WorldWideScience

Sample records for free-space quantum cryptography

  1. Practical free space quantum cryptography

    International Nuclear Information System (INIS)

    Schmitt-Manderbach, T.; Weier, H.; Regner, N.; Kurtsiefer, C.; Weinfurter, H.

    2005-01-01

    Full text: Quantum cryptography, the secure key distribution between two parties, is the first practical application of quantum information technology. By encoding digital information into different polarization states of single photons, a string of key bits can be established between two parties, where laws of quantum mechanics ensure that a possible eavesdropper has negligible knowledge of. Having shown the feasibility of a long distance quantum key distribution scheme, the emphasis of this work is to incorporate the previously developed compact sender and receiver modules into a quantum cryptography system suitable for every-day use in metropolitan areas. The permanent installation with automatic alignment allows to investigate in detail the sensitivity of the free space optical link to weather conditions and air turbulences commonly encountered in urban areas. We report on a successful free space quantum cryptography experiment over a distance of 500 m between the rooftops of two university buildings using the BB84 protocol. The obtained bit error rates in first runs of this experiment using faint coherent pulses with an average photon number ranging from 0.1 to 1.0 was measured to be below 3 percent for experiments carried out during night, leading to average raw key rates (before error correction and privacy amplification) of 50 kBits per second. Thanks to its simplicity of implementation, our experiment brings free space quantum key distribution a big step closer to practical usability in metropolitan networks and on a level with fibre-based quantum cryptography that up to now offers the only ready-to-use systems available. Compact and automated free space hardware is also a prerequisite for a possible earth-satellite quantum key distribution system in order to break the distance limit of about 100 km of current quantum cryptography schemes. (author)

  2. Quantum cryptography for secure free-space communications

    International Nuclear Information System (INIS)

    Hughes, R.J.; Buttler, W.T.; Kwiat, P.G.; Lamoreaux, S.K.; Luther, G.G.; Morgan, G.L.; Nordholt, J.E.; Peterson, C.G.

    1999-01-01

    The secure distribution of the secret random bit sequences known as key material, is an essential precursor to their use for the encryption and decryption of confidential communications. Quantum cryptography is a new technique for secure key distribution with single-photon transmissions: Heisenberg's uncertainty principle ensures that an adversary can neither successfully tap the key transmissions, nor evade detection (eavesdropping raises the key error rate above a threshold value). The authors have developed experimental quantum cryptography systems based on the transmission of non-orthogonal photon polarization states to generate shared key material over line-of-sight optical links. Key material is built up using the transmission of a single-photon per bit of an initial secret random sequence. A quantum-mechanically random subset of this sequence is identified, becoming the key material after a data reconciliation stage with the sender. The authors have developed and tested a free-space quantum key distribution (QKD) system over an outdoor optical path of ∼1 km at Los Alamos National Laboratory under nighttime conditions. Results show that free-space QKD can provide secure real-time key distribution between parties who have a need to communicate secretly. Finally, they examine the feasibility of surface to satellite QKD

  3. Entanglement-based Free Space Quantum Cryptography in Daylight

    Science.gov (United States)

    Gerhardt, Ilja; Peloso, Matthew P.; Ho, Caleb; Lamas-Linares, Antia; Kurtsiefer, Christian

    2009-05-01

    In quantum key distribution (QKD) two families of protocols are established: One, based on preparing and sending approximations of single photons, the other based on measurements on entangled photon pairs, which allow to establish a secret key using less assumptions on the size of a Hilbert space. The larger optical bandwidth of photon pairs in comparison with light used for the first family makes establishing a free space link challenging. We present a complete entanglement based QKD system following the BBM92 protocol, which generates a secure key continuously 24 hours a day between distant parties. Spectral, spatial and temporal filtering schemes were introduced to a previous setup, suppressing more than 30,B of background. We are able to establish the link during daytime, and have developed an algorithm to start and maintain time synchronization with simple crystal oscillators.

  4. Free space relativistic quantum cryptography with faint laser pulses

    International Nuclear Information System (INIS)

    Molotkov, S N; Potapova, T A

    2013-01-01

    A new protocol for quantum key distribution through empty space is proposed. Apart from the quantum mechanical restrictions on distinguishability of non-orthogonal states, the protocol employs additional restrictions imposed by special relativity. The protocol ensures generation of a secure key even for the source generating non-strictly single-photon quantum states and for arbitrary losses in quantum communication channel. (letter)

  5. Development of the polarization tracking scheme for free-space quantum cryptography

    Science.gov (United States)

    Toyoshima, Morio; Takayama, Yoshihisa; Kunimori, Hiroo; Takeoka, Masahiro; Fujiwara, Mikio; Sasaki, Masahide

    2008-04-01

    Quantum cryptography is a new technique for transmitting quantum information. The information is securely transmitted due to the laws of physics. In such systems, the vehicle that transfers quantum information is a single photon. The problem with using photons is that the transmission distance is limited by the absorption of the photons by the optical fiber along which they pass. The maximum demonstrated range so far is approximately 100 km. Using free-space quantum cryptography between a ground station and a satellite is a possible way of sending quantum information farther than is possible with optical fibers. This is because there is no birefringence effect in the atmosphere. However, there is a complication in that the directions of the polarization basis between the transmitter and the receiver must coincide with each other. This polarization changes because the mobile terminals for free-space transmission continuously change their attitudes. If the transmission protocol is based on polarization, it is necessary to compensate for the change in attitude between the mobile terminals. We are developing a scheme to track the polarization basis between the transceivers. The preliminary result is presented.

  6. On a two-pass scheme without a faraday mirror for free-space relativistic quantum cryptography

    Energy Technology Data Exchange (ETDEWEB)

    Kravtsov, K. S.; Radchenko, I. V. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation); Korol' kov, A. V. [Academy of Cryptography (Russian Federation); Kulik, S. P., E-mail: sergei.kulik@gmail.com [Moscow State University (Russian Federation); Molotkov, S. N., E-mail: sergei.molotkov@gmail.com [Academy of Cryptography (Russian Federation)

    2013-05-15

    The stability of destructive interference independent of the input polarization and the state of a quantum communication channel in fiber optic systems used in quantum cryptography plays a principal role in providing the security of communicated keys. A novel optical scheme is proposed that can be used both in relativistic quantum cryptography for communicating keys in open space and for communicating them over fiber optic lines. The scheme ensures stability of destructive interference and admits simple automatic balancing of a fiber interferometer.

  7. On a two-pass scheme without a faraday mirror for free-space relativistic quantum cryptography

    International Nuclear Information System (INIS)

    Kravtsov, K. S.; Radchenko, I. V.; Korol’kov, A. V.; Kulik, S. P.; Molotkov, S. N.

    2013-01-01

    The stability of destructive interference independent of the input polarization and the state of a quantum communication channel in fiber optic systems used in quantum cryptography plays a principal role in providing the security of communicated keys. A novel optical scheme is proposed that can be used both in relativistic quantum cryptography for communicating keys in open space and for communicating them over fiber optic lines. The scheme ensures stability of destructive interference and admits simple automatic balancing of a fiber interferometer.

  8. Quantum cryptography

    International Nuclear Information System (INIS)

    Tittel, W.; Brendel, J.; Gissin, N.; Ribordy, G.; Zbinden, H.

    1999-01-01

    The principles of quantum cryptography based on non-local correlations of entanglement photons are outlined. The method of coding and decoding of information and experiments is also described. The prospects of the technique are briefly discussed. (Z.J.)

  9. Post-Quantum Cryptography

    DEFF Research Database (Denmark)

    Gauthier Umana, Valérie

    . The public key cryptosystems that can resist these emerging attacks are called quantum resistant or post-quantum cryptosystems. There are mainly four classes of public-key cryptography that are believed to resist classical and quantum attacks: code-based cryptography, hash-based cryptography, lattice......-based cryptography and multivariate public-key cryptography. In this thesis, we focus on the rst two classes. In the rst part, we introduce coding theory and give an overview of code-based cryptography. The main contribution is an attack on two promising variants of McEliece's cryptosystem, based on quasi...

  10. Focus on Quantum Cryptography

    International Nuclear Information System (INIS)

    Kwiat, Paul G.

    2002-01-01

    Full text: In our modern era of telecommunications and the Internet, information has become a valuable commodity. Sometimes it must therefore be protected against theft - in this case, loss of secret information to an eavesdropper. Most of today's transactions are protected using encryption unproven to be secure against a computational attack by a classical computer and, in fact, the standardly used encryption algorithms are provably vulnerable to the mind-boggling parallelism of a quantum computer, should one ever be physically realized. Enter quantum cryptography. Underlying nearly all forms of encryption is the necessity for a truly secret key, a random string of zeros and ones; the basic notion of quantum cryptography is to employ single photon transmissions (or the closest attainable approximation to these) to distribute the random key material, while removing the threat of an undetected eavesdropper. Now, nearly twenty years since the seminal quantum cryptography paper by Bennett and Brassard (Bennett C H and Brassard G 1984 Proc. IEEE Int. Conf. on Computers, Systems, and Signal Processing (Bangalore) (New York: IEEE) pp 175-9), we take a look at several state-of-the-art implementations, and glimpse how future quantum cryptosystems might look. We start with papers from three of the world's leading experimental quantum cryptography efforts: Stucki et al and Bethune and Risk describe working systems for quantum key distribution (QKD) over telecommunications fibres (at 1550 nanometres and 1300 nanometres, respectively). The former's achievement of quantum key exchange over 67 kilometres of optical fibre is a world record, as is the experimental demonstration by Hughes et al of daylight free-space QKD over a 10 km atmospheric range. Next, Luetkenhaus and Jahma explore the possible vulnerabilities of such systems (which employ attenuated laser pulses instead of actual single photon states) to conceivable future eavesdropping technologies. Enzer et al have

  11. A NEW ERA OF CRYPTOGRAPHY: QUANTUM CRYPTOGRAPHY

    OpenAIRE

    Sandeepak Bhandari

    2016-01-01

    ABSTRACT Security is the first priority in today digital world for secure communication between sender and receiver. Various Cryptography techniques are developed time to time for secure communication. Quantum Cryptography is one of the latest and advanced cryptography technique, it is different from all other cryptography technique and more secure. It based on the Quantum of physics since its name which make it more secure from all other cryptography and UN breakable. In this paper about...

  12. Broadband Quantum Cryptography

    CERN Document Server

    Rogers, Daniel

    2010-01-01

    Quantum cryptography is a rapidly developing field that draws from a number of disciplines, from quantum optics to information theory to electrical engineering. By combining some fundamental quantum mechanical principles of single photons with various aspects of information theory, quantum cryptography represents a fundamental shift in the basis for security from numerical complexity to the fundamental physical nature of the communications channel. As such, it promises the holy grail of data security: theoretically unbreakable encryption. Of course, implementing quantum cryptography in real br

  13. Post-quantum cryptography.

    Science.gov (United States)

    Bernstein, Daniel J; Lange, Tanja

    2017-09-13

    Cryptography is essential for the security of online communication, cars and implanted medical devices. However, many commonly used cryptosystems will be completely broken once large quantum computers exist. Post-quantum cryptography is cryptography under the assumption that the attacker has a large quantum computer; post-quantum cryptosystems strive to remain secure even in this scenario. This relatively young research area has seen some successes in identifying mathematical operations for which quantum algorithms offer little advantage in speed, and then building cryptographic systems around those. The central challenge in post-quantum cryptography is to meet demands for cryptographic usability and flexibility without sacrificing confidence.

  14. Post-quantum cryptography

    Science.gov (United States)

    Bernstein, Daniel J.; Lange, Tanja

    2017-09-01

    Cryptography is essential for the security of online communication, cars and implanted medical devices. However, many commonly used cryptosystems will be completely broken once large quantum computers exist. Post-quantum cryptography is cryptography under the assumption that the attacker has a large quantum computer; post-quantum cryptosystems strive to remain secure even in this scenario. This relatively young research area has seen some successes in identifying mathematical operations for which quantum algorithms offer little advantage in speed, and then building cryptographic systems around those. The central challenge in post-quantum cryptography is to meet demands for cryptographic usability and flexibility without sacrificing confidence.

  15. Threshold quantum cryptography

    International Nuclear Information System (INIS)

    Tokunaga, Yuuki; Okamoto, Tatsuaki; Imoto, Nobuyuki

    2005-01-01

    We present the concept of threshold collaborative unitary transformation or threshold quantum cryptography, which is a kind of quantum version of threshold cryptography. Threshold quantum cryptography states that classical shared secrets are distributed to several parties and a subset of them, whose number is greater than a threshold, collaborates to compute a quantum cryptographic function, while keeping each share secretly inside each party. The shared secrets are reusable if no cheating is detected. As a concrete example of this concept, we show a distributed protocol (with threshold) of conjugate coding

  16. Quantum cryptography communication technology

    International Nuclear Information System (INIS)

    Cho, Jai Wan; Choi, Young Soo; Lee, Jae Chul; Choi, Yu Rak; Jung, Gwang Il; Jung, Jong Eun; Hong, Seok Boong; Koo, In Soo

    2007-09-01

    Quantum cryptography communication based on quantum mechanics provides and unconditional security between two users. Even though huge advance has been done since the 1984, having a complete system is still far away. In the case of real quantum cryptography communication systems, an unconditional security level is lowered by the imperfection of the communication unit. It is important to investigate the unconditional security of quantum communication protocols based on these experimental results and implementation examples for the advanced spread all over the world. The Japanese report, titled, 'Investigation report on the worldwide trends of quantum cryptography communications systems' was translated and summarized in this report. An unconditional security theory of the quantum cryptography and real implementation examples in the domestic area are investigated also. The goal of the report is to make quantum cryptography communication more useful and reliable alternative telecommunication infrastructure as the one of the cyber security program of the class 1-E communication system of nuclear power plant. Also another goal of this report is to provide the quantitative decision basis on the quantum cryptography communication when this secure communication system will be used in class 1-E communication channel of the nuclear power plant

  17. Quantum cryptography communication technology

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Jai Wan; Choi, Young Soo; Lee, Jae Chul; Choi, Yu Rak; Jung, Gwang Il; Jung, Jong Eun; Hong, Seok Boong; Koo, In Soo

    2007-09-15

    Quantum cryptography communication based on quantum mechanics provides and unconditional security between two users. Even though huge advance has been done since the 1984, having a complete system is still far away. In the case of real quantum cryptography communication systems, an unconditional security level is lowered by the imperfection of the communication unit. It is important to investigate the unconditional security of quantum communication protocols based on these experimental results and implementation examples for the advanced spread all over the world. The Japanese report, titled, 'Investigation report on the worldwide trends of quantum cryptography communications systems' was translated and summarized in this report. An unconditional security theory of the quantum cryptography and real implementation examples in the domestic area are investigated also. The goal of the report is to make quantum cryptography communication more useful and reliable alternative telecommunication infrastructure as the one of the cyber security program of the class 1-E communication system of nuclear power plant. Also another goal of this report is to provide the quantitative decision basis on the quantum cryptography communication when this secure communication system will be used in class 1-E communication channel of the nuclear power plant.

  18. Quantum cryptography; Kvantova kryptografie

    Energy Technology Data Exchange (ETDEWEB)

    Tittel, W; Brendel, J; Gissin, N; Ribordy, G; Zbinden, H [GAP-Optique, Universite de Geneve, 20 reu de l' Ecole de Medicine, Genf (Switzerland)

    1999-07-01

    The principles of quantum cryptography based on non-local correlations of entanglement photons are outlined. The method of coding and decoding of information and experiments is also described. The prospects of the technique are briefly discussed. (Z.J.)

  19. Relativistic quantum cryptography

    International Nuclear Information System (INIS)

    Molotkov, S. N.

    2011-01-01

    A new protocol of quantum key distribution is proposed to transmit keys through free space. Along with quantum-mechanical restrictions on the discernibility of nonorthogonal quantum states, the protocol uses additional restrictions imposed by special relativity theory. Unlike all existing quantum key distribution protocols, this protocol ensures key secrecy for a not strictly one-photon source of quantum states and an arbitrary length of a quantum communication channel.

  20. Counterfactual quantum cryptography.

    Science.gov (United States)

    Noh, Tae-Gon

    2009-12-04

    Quantum cryptography allows one to distribute a secret key between two remote parties using the fundamental principles of quantum mechanics. The well-known established paradigm for the quantum key distribution relies on the actual transmission of signal particle through a quantum channel. In this Letter, we show that the task of a secret key distribution can be accomplished even though a particle carrying secret information is not in fact transmitted through the quantum channel. The proposed protocols can be implemented with current technologies and provide practical security advantages by eliminating the possibility that an eavesdropper can directly access the entire quantum system of each signal particle.

  1. Low Cost and Compact Quantum Cryptography

    OpenAIRE

    Duligall, J. L.; Godfrey, M. S.; Harrison, K. A.; Munro, W. J.; Rarity, J. G.

    2006-01-01

    We present the design of a novel free-space quantum cryptography system, complete with purpose-built software, that can operate in daylight conditions. The transmitter and receiver modules are built using inexpensive off-the-shelf components. Both modules are compact allowing the generation of renewed shared secrets on demand over a short range of a few metres. An analysis of the software is shown as well as results of error rates and therefore shared secret yields at varying background light...

  2. Applied quantum cryptography

    International Nuclear Information System (INIS)

    Kollmitzer, Christian; Pivk, Mario

    2010-01-01

    Using the quantum properties of single photons to exchange binary keys between two partners for subsequent encryption of secret data is an absolutely novel technology. Only a few years ago quantum cryptography - or better: quantum key distribution - was the domain of basic research laboratories at universities. But during the last few years things changed. QKD left the laboratories and was picked up by more practical oriented teams that worked hard to develop a practically applicable technology out of the astonishing results of basic research. One major milestone towards a QKD technology was a large research and development project funded by the European Commission that aimed at combining quantum physics with complementary technologies that are necessary to create a technical solution: electronics, software, and network components were added within the project SECOQC (Development of a Global Network for Secure Communication based on Quantum Cryptography) that teamed up all expertise on European level to get a technology for future encryption. The practical application of QKD in a standard optical fibre network was demonstrated October 2008 in Vienna, giving a glimpse of the future of secure communication. Although many steps have still to be done in order to achieve a real mature technology, the corner stone for future secure communication is already laid. QKD will not be the Holy Grail of security, it will not be able to solve all problems for evermore. But QKD has the potential to replace one of the weakest parts of symmetric encryption: the exchange of the key. It can be proven that the key exchange process cannot be corrupted and that keys that are generated and exchanged quantum cryptographically will be secure for ever (as long as some additional conditions are kept). This book will show the state of the art of Quantum Cryptography and it will sketch how it can be implemented in standard communication infrastructure. The growing vulnerability of sensitive

  3. Autocompensating quantum cryptography

    International Nuclear Information System (INIS)

    Bethune, Donald S.; Risk, William P.

    2002-01-01

    Quantum cryptographic key distribution (QKD) uses extremely faint light pulses to carry quantum information between two parties (Alice and Bob), allowing them to generate a shared, secret cryptographic key. Autocompensating QKD systems automatically and passively compensate for uncontrolled time-dependent variations of the optical fibre properties by coding the information as a differential phase between orthogonally polarized components of a light pulse sent on a round trip through the fibre, reflected at mid-course using a Faraday mirror. We have built a prototype system based on standard telecom technology that achieves a privacy-amplified bit generation rate of ∼1000 bits s -1 over a 10 km optical fibre link. Quantum cryptography is an example of an application that, by using quantum states of individual particles to represent information, accomplishes a practical task that is impossible using classical means. (author)

  4. Composability in quantum cryptography

    International Nuclear Information System (INIS)

    Mueller-Quade, Joern; Renner, Renato

    2009-01-01

    If we combine two secure cryptographic systems, is the resulting system still secure? Answering this question is highly nontrivial and has recently sparked a considerable research effort, in particular, in the area of classical cryptography. A central insight was that the answer to the question is yes, but only within a well-specified composability framework and for carefully chosen security definitions. In this article, we review several aspects of composability in the context of quantum cryptography. The first part is devoted to key distribution. We discuss the security criteria that a quantum key distribution (QKD) protocol must fulfill to allow its safe use within a larger security application (e.g. for secure message transmission); and we demonstrate-by an explicit example-what can go wrong if conventional (non-composable) security definitions are used. Finally, to illustrate the practical use of composability, we show how to generate a continuous key stream by sequentially composing rounds of a QKD protocol. In the second part, we take a more general point of view, which is necessary for the study of cryptographic situations involving, for example, mutually distrustful parties. We explain the universal composability (UC) framework and state the composition theorem that guarantees that secure protocols can securely be composed to larger applications. We focus on the secure composition of quantum protocols into unconditionally secure classical protocols. However, the resulting security definition is so strict that some tasks become impossible without additional security assumptions. Quantum bit commitment is impossible in the UC framework even with mere computational security. Similar problems arise in the quantum bounded storage model and we observe a trade-off between the UC and the use of the weakest possible security assumptions.

  5. Relativistic quantum cryptography

    International Nuclear Information System (INIS)

    Radchenko, I V; Kravtsov, K S; Kulik, S P; Molotkov, S N

    2014-01-01

    Quantum key distribution (QKD) is a concept of secret key exchange supported by fundamentals of quantum physics. Its perfect realization offers unconditional key security, however, known practical schemes are potentially vulnerable if the quantum channel loss exceeds a certain realization-specific bound. This discrepancy is caused by the fact that any practical photon source has a non-zero probability of emitting two or more photons at a time, while theory needs exactly one. We report an essentially different QKD scheme based on both quantum physics and theory of relativity. It works flawlessly with practical photon sources at arbitrary large channel loss. Our scheme is naturally tailored for free-space optical channels, and may be used in ground-to-satellite communications, where losses are prohibitively large and unpredictable for conventional QKD. (letters)

  6. Quantum cryptography: towards realization in realistic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Imoto, M; Koashi, M; Shimizu, K [NTT Basic Research Laboratories, 3-1 Morinosato-Wakamiya, Atsugi-shi, Kanagawa 243-01 (Japan); Huttner, B [Universite de Geneve, GAP-optique, 20, Rue de l` Ecole de Medecine CH1211, Geneve 4 (Switzerland)

    1997-05-11

    Many of quantum cryptography schemes have been proposed based on some assumptions such as no transmission loss, no measurement error, and an ideal single photon generator. We have been trying to develop a theory of quantum cryptography considering realistic conditions. As such attempts, we propose quantum cryptography with coherent states, quantum cryptography with two-photon interference, and generalization of two-state cryptography to two-mixed-state cases. (author) 15 refs., 1 fig., 1 tab.

  7. Quantum cryptography: towards realization in realistic conditions

    International Nuclear Information System (INIS)

    Imoto, M.; Koashi, M.; Shimizu, K.; Huttner, B.

    1997-01-01

    Many of quantum cryptography schemes have been proposed based on some assumptions such as no transmission loss, no measurement error, and an ideal single photon generator. We have been trying to develop a theory of quantum cryptography considering realistic conditions. As such attempts, we propose quantum cryptography with coherent states, quantum cryptography with two-photon interference, and generalization of two-state cryptography to two-mixed-state cases. (author)

  8. Mesoscopic quantum cryptography

    Energy Technology Data Exchange (ETDEWEB)

    Molotkov, S. N., E-mail: sergei.molotkov@gmail.com [Russian Academy of Sciences, Institute of Solid State Physics (Russian Federation)

    2017-03-15

    Since a strictly single-photon source is not yet available, in quantum cryptography systems, one uses, as information quantum states, coherent radiation of a laser with an average number of photons of μ ≈ 0.1–0.5 in a pulse, attenuated to the quasi-single-photon level. The linear independence of a set of coherent quasi-single-photon information states leads to the possibility of unambiguous measurements that, in the presence of losses in the line, restrict the transmission range of secret keys. Starting from a certain value of critical loss (the length of the line), the eavesdropper knows the entire key, does not make errors, and is not detected—the distribution of secret keys becomes impossible. This problem is solved by introducing an additional reference state with an average number of photons of μ{sub cl} ≈ 10{sup 3}–10{sup 6}, depending on the length of the communication line. It is shown that the use of a reference state does not allow the eavesdropper to carry out measurements with conclusive outcome while remaining undetected. A reference state guarantees detecting an eavesdropper in a channel with high losses. In this case, information states may contain a mesoscopic average number of photons in the range of μ{sub q} ≈ 0.5–10{sup 2}. The protocol proposed is easy to implement technically, admits flexible adjustment of parameters to the length of the communication line, and is simple and transparent for proving the secrecy of keys.

  9. Quantum cryptography beyond quantum key distribution

    NARCIS (Netherlands)

    Broadbent, A.; Schaffner, C.

    2016-01-01

    Quantum cryptography is the art and science of exploiting quantum mechanical effects in order to perform cryptographic tasks. While the most well-known example of this discipline is quantum key distribution (QKD), there exist many other applications such as quantum money, randomness generation,

  10. A prototype quantum cryptography system

    Energy Technology Data Exchange (ETDEWEB)

    Surasak, Chiangga

    1998-07-01

    In this work we have constructed a new secure quantum key distribution system based on the BB84 protocol. Many current state-of-the-art quantum cryptography systems encounter major problems concerning low bit rate, synchronization, and stabilization. Our quantum cryptography system utilizes only laser diodes and standard passive optical components, to enhance the stability and also to decrease the space requirements. The development of this demonstration for a practical quantum key distribution system is a consequence of our previous work on the quantum cryptographic system using optical fiber components for the transmitter and receiver. There we found that the optical fiber couplers should not be used due to the problems with space, stability and alignment. The goal of the synchronization is to use as little transmission capacities as possible. The experimental results of our quantum key distribution system show the feasibility of getting more than 90 % transmission capacities with the approaches developed in this work. Therefore it becomes feasible to securely establish a random key sequence at a rate of 1 to {approx} 5K bit/s by using our stable, compact, cheap, and user-friendly modules for quantum cryptography. (author)

  11. A prototype quantum cryptography system

    International Nuclear Information System (INIS)

    Chiangga Surasak

    1998-07-01

    In this work we have constructed a new secure quantum key distribution system based on the BB84 protocol. Many current state-of-the-art quantum cryptography systems encounter major problems concerning low bit rate, synchronization, and stabilization. Our quantum cryptography system utilizes only laser diodes and standard passive optical components, to enhance the stability and also to decrease the space requirements. The development of this demonstration for a practical quantum key distribution system is a consequence of our previous work on the quantum cryptographic system using optical fiber components for the transmitter and receiver. There we found that the optical fiber couplers should not be used due to the problems with space, stability and alignment. The goal of the synchronization is to use as little transmission capacities as possible. The experimental results of our quantum key distribution system show the feasibility of getting more than 90 % transmission capacities with the approaches developed in this work. Therefore it becomes feasible to securely establish a random key sequence at a rate of 1 to ∼ 5K bit/s by using our stable, compact, cheap, and user-friendly modules for quantum cryptography. (author)

  12. Free-Space Quantum Communication with a Portable Quantum Memory

    Science.gov (United States)

    Namazi, Mehdi; Vallone, Giuseppe; Jordaan, Bertus; Goham, Connor; Shahrokhshahi, Reihaneh; Villoresi, Paolo; Figueroa, Eden

    2017-12-01

    The realization of an elementary quantum network that is intrinsically secure and operates over long distances requires the interconnection of several quantum modules performing different tasks. In this work, we report the realization of a communication network functioning in a quantum regime, consisting of four different quantum modules: (i) a random polarization qubit generator, (ii) a free-space quantum-communication channel, (iii) an ultralow-noise portable quantum memory, and (iv) a qubit decoder, in a functional elementary quantum network possessing all capabilities needed for quantum-information distribution protocols. We create weak coherent pulses at the single-photon level encoding polarization states |H ⟩ , |V ⟩, |D ⟩, and |A ⟩ in a randomized sequence. The random qubits are sent over a free-space link and coupled into a dual-rail room-temperature quantum memory and after storage and retrieval are analyzed in a four-detector polarization analysis akin to the requirements of the BB84 protocol. We also show ultralow noise and fully portable operation, paving the way towards memory-assisted all-environment free-space quantum cryptographic networks.

  13. Relativistic quantum cryptography

    Science.gov (United States)

    Kaniewski, Jedrzej

    Special relativity states that information cannot travel faster than the speed of light, which means that communication between agents occupying distinct locations incurs some minimal delay. Alternatively, we can see it as temporary communication constraints between distinct agents and such constraints turn out to be useful for cryptographic purposes. In relativistic cryptography we consider protocols in which interactions occur at distinct locations at well-defined times and we investigate why such a setting allows to implement primitives which would not be possible otherwise. (Abstract shortened by UMI.).

  14. Optimization problem in quantum cryptography

    International Nuclear Information System (INIS)

    Brandt, Howard E

    2003-01-01

    A complete optimization was recently performed, yielding the maximum information gain by a general unitary entangling probe in the four-state protocol of quantum cryptography. A larger set of optimum probe parameters was found than was known previously from an incomplete optimization. In the present work, a detailed comparison is made between the complete and incomplete optimizations. Also, a new set of optimum probe parameters is identified for the four-state protocol

  15. Key distillation in quantum cryptography

    Science.gov (United States)

    Slutsky, Boris Aron

    1998-11-01

    Quantum cryptography is a technique which permits two parties to communicate over an open channel and establish a shared sequence of bits known only to themselves. This task, provably impossible in classical cryptography, is accomplished by encoding the data on quantum particles and harnessing their unique properties. It is believed that no eavesdropping attack consistent with the laws of quantum theory can compromise the secret data unknowingly to the legitimate users of the channel. Any attempt by a hostile actor to monitor the data carrying particles while in transit reveals itself through transmission errors it must inevitably introduce. Unfortunately, in practice a communication is not free of errors even when no eavesdropping is present. Key distillation is a technique that permits the parties to overcome this difficulty and establish a secret key despite channel defects, under the assumption that every particle is handled independently from other particles by the enemy. In the present work, key distillation is described and its various aspects are studied. A relationship is derived between the average error rate resulting from an eavesdropping attack and the amount of information obtained by the attacker. Formal definition is developed of the security of the final key. The net throughput of secret bits in a quantum cryptosystem employing key distillation is assessed. An overview of quantum cryptographic protocols and related information theoretical results is also given.

  16. Quantum-chaotic cryptography

    Science.gov (United States)

    de Oliveira, G. L.; Ramos, R. V.

    2018-03-01

    In this work, it is presented an optical scheme for quantum key distribution employing two synchronized optoelectronic oscillators (OEO) working in the chaotic regime. The produced key depends on the chaotic dynamic, and the synchronization between Alice's and Bob's OEOs uses quantum states. An attack on the synchronization signals will disturb the synchronization of the chaotic systems increasing the error rate in the final key.

  17. Protocols and plan of quantum cryptography

    Directory of Open Access Journals (Sweden)

    Milorad S. Markagić

    2012-01-01

    Full Text Available Along with the development of confidentiality of data and resources, there is a need to develop systems that would provide confidentiality. Currently, the most used systems are classical cryptographic systems and encryption public key systems. However, none of these systems provides a solution for the famous 'catch 22' of cryptography. Owing to the intensive development of quantum mechanics, in the last 30 years emerged an entirely new kind of cryptography-quantum cryptography. Its greatest contribution is a possibility to discover an intercepted communication channel from a third party. The question is: is this really true? The question arises: 'If the quantum cryptography is so good, why is not widely used?' The aim of this paper is, on the one hand, to define the basic mechanisms of quantum cryptography IP, and, on the other hand, to point to the shortcomings, as they related to the opportunities of today's devices and flaws in protocols.

  18. Cryptography, quantum computation and trapped ions

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, Richard J.

    1998-03-01

    The significance of quantum computation for cryptography is discussed. Following a brief survey of the requirements for quantum computational hardware, an overview of the ion trap quantum computation project at Los Alamos is presented. The physical limitations to quantum computation with trapped ions are analyzed and an assessment of the computational potential of the technology is made.

  19. Quantum cryptography: The power of independence

    Science.gov (United States)

    Ekert, Artur

    2018-02-01

    Device-independent quantum cryptography promises unprecedented security, but it is regarded as a theorist's dream and an experimentalist's nightmare. A new mathematical tool has now pushed its experimental demonstration much closer to reality.

  20. Quantum key distribution and cryptography

    International Nuclear Information System (INIS)

    Alleaume, R.

    2005-01-01

    Full text: Originally proposed by classical cryptographers, the ideas behind Quantum Key Distribution (QKD) have attracted considerable interest among the quantum optics community, which has significantly helped bring these ideas to reality. Experimental realizations have quickly evolved from early lab demonstrations to QKD systems that are now deployed in real conditions and targeting commercial applications. Although QKD can be theoretically proven to rely on 'unconditional security proofs' and should thus be able to provide security levels unachievable through computationally-based cryptographic techniques, the debate on the cryptographic applications of QKD remains somehow controversial. It seems that a consensus on that matter cannot be reached without a careful analysis of assumptions and definitions related to security models used in classical or in quantum cryptography. In this talk, we will try to present a comprehensive synthesis on this topic. We have initiated this work as a contribution to the European IP SECOQC project, confronting views and knowledge among experimental and theoretical quantum physicists, as well as classical cryptographers. (author)

  1. Free-space entangled quantum carpets

    Science.gov (United States)

    Barros, Mariana R.; Ketterer, Andreas; Farías, Osvaldo Jiménez; Walborn, Stephen P.

    2017-04-01

    The Talbot effect in quantum physics is known to produce intricate patterns in the probability distribution of a particle, known as "quantum carpets," corresponding to the revival and replication of the initial wave function. Recently, it was shown that one can encode a D -level qudit in such a way that the Talbot effect can be used to process the D -dimensional quantum information [Farías et al., Phys. Rev. A 91, 062328 (2015), 10.1103/PhysRevA.91.062328]. Here we introduce a scheme to produce free-propagating "entangled quantum carpets" with pairs of photons produced by spontaneous parametric down-conversion. First we introduce an optical device that can be used to synthesize arbitrary superposition states of Talbot qudits. Sending spatially entangled photon pairs through a pair of these devices produces an entangled pair of qudits. As an application, we show how the Talbot effect can be used to test a D -dimensional Bell inequality. Numerical simulations show that violation of the Bell inequality depends strongly on the amount of spatial correlation in the initial two-photon state. We briefly discuss how our optical scheme might be adapted to matter wave experiments.

  2. Distinguishability of quantum states and shannon complexity in quantum cryptography

    Science.gov (United States)

    Arbekov, I. M.; Molotkov, S. N.

    2017-07-01

    The proof of the security of quantum key distribution is a rather complex problem. Security is defined in terms different from the requirements imposed on keys in classical cryptography. In quantum cryptography, the security of keys is expressed in terms of the closeness of the quantum state of an eavesdropper after key distribution to an ideal quantum state that is uncorrelated to the key of legitimate users. A metric of closeness between two quantum states is given by the trace metric. In classical cryptography, the security of keys is understood in terms of, say, the complexity of key search in the presence of side information. In quantum cryptography, side information for the eavesdropper is given by the whole volume of information on keys obtained from both quantum and classical channels. The fact that the mathematical apparatuses used in the proof of key security in classical and quantum cryptography are essentially different leads to misunderstanding and emotional discussions [1]. Therefore, one should be able to answer the question of how different cryptographic robustness criteria are related to each other. In the present study, it is shown that there is a direct relationship between the security criterion in quantum cryptography, which is based on the trace distance determining the distinguishability of quantum states, and the criterion in classical cryptography, which uses guesswork on the determination of a key in the presence of side information.

  3. Counterfactual quantum cryptography network with untrusted relay

    Science.gov (United States)

    Chen, Yuanyuan; Gu, Xuemei; Jiang, Dong; Xie, Ling; Chen, Lijun

    2015-07-01

    Counterfactual quantum cryptography allows two remote parties to share a secret key even though a physical particle is not in fact transmitted through the quantum channel. In order to extend the scope of counterfactual quantum cryptography, we use an untrusted relay to construct a multi-user network. The implementation issues are discussed to show that the scheme can be realized with current technologies. We also prove the practical security advantages of the scheme by eliminating the probability that an eavesdropper can directly access the signal or an untrusted relay can perform false operations.

  4. Quantum cryptography approaching the classical limit.

    Science.gov (United States)

    Weedbrook, Christian; Pirandola, Stefano; Lloyd, Seth; Ralph, Timothy C

    2010-09-10

    We consider the security of continuous-variable quantum cryptography as we approach the classical limit, i.e., when the unknown preparation noise at the sender's station becomes significantly noisy or thermal (even by as much as 10(4) times greater than the variance of the vacuum mode). We show that, provided the channel transmission losses do not exceed 50%, the security of quantum cryptography is not dependent on the channel transmission, and is therefore incredibly robust against significant amounts of excess preparation noise. We extend these results to consider for the first time quantum cryptography at wavelengths considerably longer than optical and find that regions of security still exist all the way down to the microwave.

  5. Conditional efficient multiuser quantum cryptography network

    International Nuclear Information System (INIS)

    Xue Peng; Li Chuanfeng; Guo Guangcan

    2002-01-01

    We propose a conditional quantum key distribution scheme with three nonorthogonal states. Combined with the idea presented by Lo et al. (H.-K. Lo, H. F. Chau, and M. Ardehali, e-print arXiv: quant-ph/0011056), the efficiency of this scheme is increased to tend to 100%. Also, such a refined data analysis guarantees the security of our scheme against the most general eavesdropping strategy. Then, based on the scheme, we present a quantum cryptography network with the addition of a device called ''space optical switch.'' Moreover, we give out a realization of a quantum random number generator. Thus, a feasible experimental scheme of this efficient quantum cryptography network is completely given

  6. EDITORIAL: Focus on Quantum Cryptography: Theory and Practice FOCUS ON QUANTUM CRYPTOGRAPHY: THEORY AND PRACTICE

    Science.gov (United States)

    Lütkenhaus, N.; Shields, A. J.

    2009-04-01

    superconducting single-photon detectors Lijun Ma, S Nam, Hai Xu, B Baek, Tiejun Chang, O Slattery, A Mink and Xiao Tang Practical gigahertz quantum key distribution based on avalanche photodiodes Z L Yuan, A R Dixon, J F Dynes, A W Sharpe and A J Shields Simple security proof of quantum key distribution based on complementarity M Koashi Feasibility of satellite quantum key distribution C Bonato, A Tomaello, V Da Deppo, G Naletto and P Villoresi Programmable instrumentation and gigahertz signaling for single-photon quantum communication systems Alan Mink, Joshua C Bienfang, Robert Carpenter, Lijun Ma, Barry Hershman, Alessandro Restelli and Xiao Tang Experimental polarization encoded quantum key distribution over optical fibres with real-time continuous birefringence compensation G B Xavier, N Walenta, G Vilela de Faria, G P Temporão, N Gisin, H Zbinden and J P von der Weid Feasibility of free space quantum key distribution with coherent polarization states D Elser, T Bartley, B Heim, Ch Wittmann, D Sych and G Leuchs A fully automated entanglement-based quantum cryptography system for telecom fiber networks Alexander Treiber, Andreas Poppe, Michael Hentschel, Daniele Ferrini, Thomas Lorünser, Edwin Querasser, Thomas Matyus, Hannes Hübel and Anton Zeilinger Dense wavelength multiplexing of 1550 nm QKD with strong classical channels in reconfigurable networking environments N A Peters, P Toliver, T E Chapuran, R J Runser, S R McNown, C G Peterson, D Rosenberg, N Dallmann, R J Hughes, K P McCabe, J E Nordholt and K T Tyagi Clock synchronization by remote detection of correlated photon pairs Caleb Ho, Antía Lamas-Linares and Christian Kurtsiefer Megabits secure key rate quantum key distribution Q Zhang, H Takesue, T Honjo, K Wen, T Hirohata, M Suyama, Y Takiguchi, H Kamada, Y Tokura, O Tadanaga, Y Nishida, M Asobe and Y Yamamoto Practical long-distance quantum key distribution system using decoy levels D Rosenberg, C G Peterson, J W Harrington, P R Rice, N Dallmann, K T Tyagi, K P

  7. Quantum discord as a resource for quantum cryptography.

    Science.gov (United States)

    Pirandola, Stefano

    2014-11-07

    Quantum discord is the minimal bipartite resource which is needed for a secure quantum key distribution, being a cryptographic primitive equivalent to non-orthogonality. Its role becomes crucial in device-dependent quantum cryptography, where the presence of preparation and detection noise (inaccessible to all parties) may be so strong to prevent the distribution and distillation of entanglement. The necessity of entanglement is re-affirmed in the stronger scenario of device-independent quantum cryptography, where all sources of noise are ascribed to the eavesdropper.

  8. Spectral coherent-state quantum cryptography.

    Science.gov (United States)

    Cincotti, Gabriella; Spiekman, Leo; Wada, Naoya; Kitayama, Ken-ichi

    2008-11-01

    A novel implementation of quantum-noise optical cryptography is proposed, which is based on a simplified architecture that allows long-haul, high-speed transmission in a fiber optical network. By using a single multiport encoder/decoder and 16 phase shifters, this new approach can provide the same confidentiality as other implementations of Yuen's encryption protocol, which use a larger number of phase or polarization coherent states. Data confidentiality and error probability for authorized and unauthorized receivers are carefully analyzed.

  9. High-rate measurement-device-independent quantum cryptography

    DEFF Research Database (Denmark)

    Pirandola, Stefano; Ottaviani, Carlo; Spedalieri, Gaetana

    2015-01-01

    Quantum cryptography achieves a formidable task - the remote distribution of secret keys by exploiting the fundamental laws of physics. Quantum cryptography is now headed towards solving the practical problem of constructing scalable and secure quantum networks. A significant step in this direction...

  10. Position-based quantum cryptography and catalytic computation

    NARCIS (Netherlands)

    Speelman, F.

    2016-01-01

    In this thesis, we present several results along two different lines of research. The first part concerns the study of position-based quantum cryptography, a topic in quantum cryptography. By combining quantum mechanics with special relativity theory, new cryptographic tasks can be developed that

  11. Experimental quantum secret sharing and third-man quantum cryptography.

    Science.gov (United States)

    Chen, Yu-Ao; Zhang, An-Ning; Zhao, Zhi; Zhou, Xiao-Qi; Lu, Chao-Yang; Peng, Cheng-Zhi; Yang, Tao; Pan, Jian-Wei

    2005-11-11

    Quantum secret sharing (QSS) and third-man quantum cryptography (TQC) are essential for advanced quantum communication; however, the low intensity and fragility of the multiphoton entanglement source in previous experiments have made their realization an extreme experimental challenge. Here, we develop and exploit an ultrastable high intensity source of four-photon entanglement to report an experimental realization of QSS and TQC. The technology developed in our experiment will be important for future multiparty quantum communication.

  12. Free-space communication based on quantum cascade laser

    International Nuclear Information System (INIS)

    Liu Chuanwei; Zhai Shenqiang; Zhang Jinchuan; Zhou Yuhong; Jia Zhiwei; Liu Fengqi; Wang Zhanguo

    2015-01-01

    A free-space communication based on a mid-infrared quantum cascade laser (QCL) is presented. A room-temperature continuous-wave distributed-feedback (DFB) QCL combined with a mid-infrared detector comprise the basic unit of the communication system. Sinusoidal signals at a highest frequency of 40 MHz and modulated video signals with a carrier frequency of 30 MHz were successfully transmitted with this experimental setup. Our research has provided a proof-of-concept demonstration of space optical communication application with QCL. The highest operation frequency of our setup was determined by the circuit-limited modulation bandwidth. A high performance communication system can be obtained with improved modulation circuit system. (paper)

  13. Continuous time quantum random walks in free space

    Science.gov (United States)

    Eichelkraut, Toni; Vetter, Christian; Perez-Leija, Armando; Christodoulides, Demetrios; Szameit, Alexander

    2014-05-01

    We show theoretically and experimentally that two-dimensional continuous time coherent random walks are possible in free space, that is, in the absence of any external potential, by properly tailoring the associated initial wave function. These effects are experimentally demonstrated using classical paraxial light. Evidently, the usage of classical beams to explore the dynamics of point-like quantum particles is possible since both phenomena are mathematically equivalent. This in turn makes our approach suitable for the realization of random walks using different quantum particles, including electrons and photons. To study the spatial evolution of a wavefunction theoretically, we consider the one-dimensional paraxial wave equation (i∂z +1/2 ∂x2) Ψ = 0 . Starting with the initially localized wavefunction Ψ (x , 0) = exp [ -x2 / 2σ2 ] J0 (αx) , one can show that the evolution of such Gaussian-apodized Bessel envelopes within a region of validity resembles the probability pattern of a quantum walker traversing a uniform lattice. In order to generate the desired input-field in our experimental setting we shape the amplitude and phase of a collimated light beam originating from a classical HeNe-Laser (633 nm) utilizing a spatial light modulator.

  14. Experimental quantum cryptography with qutrits

    Science.gov (United States)

    Gröblacher, Simon; Jennewein, Thomas; Vaziri, Alipasha; Weihs, Gregor; Zeilinger, Anton

    2006-05-01

    We produce two identical keys using, for the first time, entangled trinary quantum systems (qutrits) for quantum key distribution. The advantage of qutrits over the normally used binary quantum systems is an increased coding density and a higher security margin. The qutrits are encoded into the orbital angular momentum of photons, namely Laguerre Gaussian modes with azimuthal index l + 1, 0 and -1, respectively. The orbital angular momentum is controlled with phase holograms. In an Ekert-type protocol the violation of a three-dimensional Bell inequality verifies the security of the generated keys. A key is obtained with a qutrit error rate of approximately 10%.

  15. Quantum information. Teleporation - cryptography - quantum computer

    International Nuclear Information System (INIS)

    Breuer, Reinhard

    2010-01-01

    The following topics are dealt with: Reality in the test house, quantum teleportation, 100 years of quantum theory, the reality of quanta, interactionless quantum measurement, rules for quantum computers, quantum computers with ions, spintronics with diamond, the limits of the quantum computers, a view into the future of quantum optics. (HSI)

  16. Fast, efficient error reconciliation for quantum cryptography

    International Nuclear Information System (INIS)

    Buttler, W.T.; Lamoreaux, S.K.; Torgerson, J.R.; Nickel, G.H.; Donahue, C.H.; Peterson, C.G.

    2003-01-01

    We describe an error-reconciliation protocol, which we call Winnow, based on the exchange of parity and Hamming's 'syndrome' for N-bit subunits of a large dataset. The Winnow protocol was developed in the context of quantum-key distribution and offers significant advantages and net higher efficiency compared to other widely used protocols within the quantum cryptography community. A detailed mathematical analysis of the Winnow protocol is presented in the context of practical implementations of quantum-key distribution; in particular, the information overhead required for secure implementation is one of the most important criteria in the evaluation of a particular error-reconciliation protocol. The increase in efficiency for the Winnow protocol is largely due to the reduction in authenticated public communication required for its implementation

  17. Quantum information. Teleportation - cryptography - quantum computer

    International Nuclear Information System (INIS)

    Koenneker, Carsten

    2012-01-01

    The following topics are dealt with: Reality in the test facility, quantum teleportation, the reality of quanta, interaction-free quantum measurement, rules for quantum computers, quantum computers with ions, spintronics with diamond, the limits of the quantum computers, a view in the future of quantum optics. (HSI)

  18. Long distance free-space quantum key distribution

    International Nuclear Information System (INIS)

    Schmitt-Manderbach, T.

    2007-01-01

    The aim of the presented experiment was to investigate the feasibility of satellite-based global quantum key distribution. In this context, a free-space quantum key distribution experiment over a real distance of 144 km was performed. The transmitter and the receiver were situated in 2500 m altitude on the Canary Islands of La Palma and Tenerife, respectively. The small and compact transmitter unit generated attenuated laser pulses, that were sent to the receiver via a 15-cm optical telescope. The receiver unit for polarisation analysis and detection of the sent pulses was integrated into an existing mirror telescope designed for classical optical satellite communications. To ensure the required stability and efficiency of the optical link in the presence of atmospheric turbulence, the two telescopes were equipped with a bi-directional automatic tracking system. Still, due to stray light and high optical attenuation, secure key exchange would not be possible using attenuated pulses in connection with the standard BB84 protocol. The photon number statistics of attenuated pulses follows a Poissonian distribution. Hence, by removing a photon from all pulses containing two or more photons, an eavesdropper could measure its polarisation without disturbing the polarisation state of the remaining pulse. In this way, he can gain information about the key without introducing detectable errors. To protect against such attacks, the presented experiment employed the recently developed method of using additional ''decoy'' states, i.e., the the intensity of the pulses created by the transmitter were varied in a random manner. By analysing the detection probabilities of the different pulses individually, a photon-number-splitting attack can be detected. Thanks to the decoy-state analysis, the secrecy of the resulting quantum key could be ensured despite the Poissonian nature of the emitted pulses. For a channel attenuation as high as 35 dB, a secret key rate of up to 250 bit

  19. Long distance free-space quantum key distribution

    Energy Technology Data Exchange (ETDEWEB)

    Schmitt-Manderbach, T.

    2007-10-16

    The aim of the presented experiment was to investigate the feasibility of satellite-based global quantum key distribution. In this context, a free-space quantum key distribution experiment over a real distance of 144 km was performed. The transmitter and the receiver were situated in 2500 m altitude on the Canary Islands of La Palma and Tenerife, respectively. The small and compact transmitter unit generated attenuated laser pulses, that were sent to the receiver via a 15-cm optical telescope. The receiver unit for polarisation analysis and detection of the sent pulses was integrated into an existing mirror telescope designed for classical optical satellite communications. To ensure the required stability and efficiency of the optical link in the presence of atmospheric turbulence, the two telescopes were equipped with a bi-directional automatic tracking system. Still, due to stray light and high optical attenuation, secure key exchange would not be possible using attenuated pulses in connection with the standard BB84 protocol. The photon number statistics of attenuated pulses follows a Poissonian distribution. Hence, by removing a photon from all pulses containing two or more photons, an eavesdropper could measure its polarisation without disturbing the polarisation state of the remaining pulse. In this way, he can gain information about the key without introducing detectable errors. To protect against such attacks, the presented experiment employed the recently developed method of using additional 'decoy' states, i.e., the the intensity of the pulses created by the transmitter were varied in a random manner. By analysing the detection probabilities of the different pulses individually, a photon-number-splitting attack can be detected. Thanks to the decoy-state analysis, the secrecy of the resulting quantum key could be ensured despite the Poissonian nature of the emitted pulses. For a channel attenuation as high as 35 dB, a secret key rate of up to 250

  20. Entropy in quantum information theory - Communication and cryptography

    DEFF Research Database (Denmark)

    Majenz, Christian

    in quantum Shannon theory. While immensely more entanglement-consuming, the variant of port based teleportation is interesting for applications like instantaneous non-local computation and attacks on quantum position-based cryptography. Port based teleportation cannot be implemented perfectly......, for vanishing error. As a byproduct, a new lower bound for the size of the program register for an approximate universal programmable quantum processor is derived. Finally, the mix is completed with a result in quantum cryptography. While quantum key distribution is the most well-known quantum cryptographic...... protocol, there has been increased interest in extending the framework of symmetric key cryptography to quantum messages. We give a new denition for information-theoretic quantum non-malleability, strengthening the previous denition by Ambainis et al. We show that quantum non-malleability implies secrecy...

  1. PREFACE: Quantum Information, Communication, Computation and Cryptography

    Science.gov (United States)

    Benatti, F.; Fannes, M.; Floreanini, R.; Petritis, D.

    2007-07-01

    The application of quantum mechanics to information related fields such as communication, computation and cryptography is a fast growing line of research that has been witnessing an outburst of theoretical and experimental results, with possible practical applications. On the one hand, quantum cryptography with its impact on secrecy of transmission is having its first important actual implementations; on the other hand, the recent advances in quantum optics, ion trapping, BEC manipulation, spin and quantum dot technologies allow us to put to direct test a great deal of theoretical ideas and results. These achievements have stimulated a reborn interest in various aspects of quantum mechanics, creating a unique interplay between physics, both theoretical and experimental, mathematics, information theory and computer science. In view of all these developments, it appeared timely to organize a meeting where graduate students and young researchers could be exposed to the fundamentals of the theory, while senior experts could exchange their latest results. The activity was structured as a school followed by a workshop, and took place at The Abdus Salam International Center for Theoretical Physics (ICTP) and The International School for Advanced Studies (SISSA) in Trieste, Italy, from 12-23 June 2006. The meeting was part of the activity of the Joint European Master Curriculum Development Programme in Quantum Information, Communication, Cryptography and Computation, involving the Universities of Cergy-Pontoise (France), Chania (Greece), Leuven (Belgium), Rennes1 (France) and Trieste (Italy). This special issue of Journal of Physics A: Mathematical and Theoretical collects 22 contributions from well known experts who took part in the workshop. They summarize the present day status of the research in the manifold aspects of quantum information. The issue is opened by two review articles, the first by G Adesso and F Illuminati discussing entanglement in continuous variable

  2. Event-by-event simulation of quantum cryptography protocols

    NARCIS (Netherlands)

    Zhao, S.; Raedt, H. De

    We present a new approach to simulate quantum cryptography protocols using event-based processes. The method is validated by simulating the BB84 protocol and the Ekert protocol, both without and with the presence of an eavesdropper.

  3. Quantum cryptography and quantification of quantum correlations

    International Nuclear Information System (INIS)

    Koashi, M

    2008-01-01

    Study of the security of quantum key distribution protocols has provided us a deeper understanding about the trade-off between the amount of information extracted from a quantum system and the disturbance left in the system as a result of the extraction process. Here we discuss how such a new development helps us to understand the quantum correlations in a quantitative way. A detailed analysis of the information-disturbance trade-off for the zero-disturbance cases leads to a simple structure theorem, and the theorem can be used to derive an exact formula for the compressibility of quantum signals, which is a measure of quantum correlations in terms of the cost to preserve them. The analysis including the nonzero disturbance cases has a very close connection to the theory of entanglement. While the distillable key is regarded as a measure of entanglement, it does not coincide with either of the two operational measures of entanglement, the distillable entanglement and the entanglement cost. We discuss the physical meaning of the difference between these three measures of entanglement by providing each of them with an alternative operational definition

  4. Efficient multiuser quantum cryptography network based on entanglement.

    Science.gov (United States)

    Xue, Peng; Wang, Kunkun; Wang, Xiaoping

    2017-04-04

    We present an efficient quantum key distribution protocol with a certain entangled state to solve a special cryptographic task. Also, we provide a proof of security of this protocol by generalizing the proof of modified of Lo-Chau scheme. Based on this two-user scheme, a quantum cryptography network protocol is proposed without any quantum memory.

  5. Proposal for founding mistrustful quantum cryptography on coin tossing

    International Nuclear Information System (INIS)

    Kent, Adrian

    2003-01-01

    A significant branch of classical cryptography deals with the problems which arise when mistrustful parties need to generate, process, or exchange information. As Kilian showed a while ago, mistrustful classical cryptography can be founded on a single protocol, oblivious transfer, from which general secure multiparty computations can be built. The scope of mistrustful quantum cryptography is limited by no-go theorems, which rule out, inter alia, unconditionally secure quantum protocols for oblivious transfer or general secure two-party computations. These theorems apply even to protocols which take relativistic signaling constraints into account. The best that can be hoped for, in general, are quantum protocols which are computationally secure against quantum attack. Here a method is described for building a classically certified bit commitment, and hence every other mistrustful cryptographic task, from a secure coin-tossing protocol. No security proof is attempted, but reasons are sketched why these protocols might resist quantum computational attack

  6. A Quantum Cryptography Communication Network Based on Software Defined Network

    Directory of Open Access Journals (Sweden)

    Zhang Hongliang

    2018-01-01

    Full Text Available With the development of the Internet, information security has attracted great attention in today’s society, and quantum cryptography communication network based on quantum key distribution (QKD is a very important part of this field, since the quantum key distribution combined with one-time-pad encryption scheme can guarantee the unconditional security of the information. The secret key generated by quantum key distribution protocols is a very valuable resource, so making full use of key resources is particularly important. Software definition network (SDN is a new type of network architecture, and it separates the control plane and the data plane of network devices through OpenFlow technology, thus it realizes the flexible control of the network resources. In this paper, a quantum cryptography communication network model based on SDN is proposed to realize the flexible control of quantum key resources in the whole cryptography communication network. Moreover, we propose a routing algorithm which takes into account both the hops and the end-to-end availible keys, so that the secret key generated by QKD can be used effectively. We also simulate this quantum cryptography communication network, and the result shows that based on SDN and the proposed routing algorithm the performance of this network is improved since the effective use of the quantum key resources.

  7. Postselection technique for quantum channels with applications to quantum cryptography.

    Science.gov (United States)

    Christandl, Matthias; König, Robert; Renner, Renato

    2009-01-16

    We propose a general method for studying properties of quantum channels acting on an n-partite system, whose action is invariant under permutations of the subsystems. Our main result is that, in order to prove that a certain property holds for an arbitrary input, it is sufficient to consider the case where the input is a particular de Finetti-type state, i.e., a state which consists of n identical and independent copies of an (unknown) state on a single subsystem. Our technique can be applied to the analysis of information-theoretic problems. For example, in quantum cryptography, we get a simple proof for the fact that security of a discrete-variable quantum key distribution protocol against collective attacks implies security of the protocol against the most general attacks. The resulting security bounds are tighter than previously known bounds obtained with help of the exponential de Finetti theorem.

  8. Practical device-independent quantum cryptography via entropy accumulation.

    Science.gov (United States)

    Arnon-Friedman, Rotem; Dupuis, Frédéric; Fawzi, Omar; Renner, Renato; Vidick, Thomas

    2018-01-31

    Device-independent cryptography goes beyond conventional quantum cryptography by providing security that holds independently of the quality of the underlying physical devices. Device-independent protocols are based on the quantum phenomena of non-locality and the violation of Bell inequalities. This high level of security could so far only be established under conditions which are not achievable experimentally. Here we present a property of entropy, termed "entropy accumulation", which asserts that the total amount of entropy of a large system is the sum of its parts. We use this property to prove the security of cryptographic protocols, including device-independent quantum key distribution, while achieving essentially optimal parameters. Recent experimental progress, which enabled loophole-free Bell tests, suggests that the achieved parameters are technologically accessible. Our work hence provides the theoretical groundwork for experimental demonstrations of device-independent cryptography.

  9. Free-space quantum electrodynamics with a single Rydberg superatom

    DEFF Research Database (Denmark)

    Paris-Mandoki, Asaf; Braun, Christoph; Kumlin, Jan

    2017-01-01

    The interaction of a single photon with an individual two-level system is the textbook example of quantum electrodynamics. Achieving strong coupling in this system has so far required confinement of the light field inside resonators or waveguides. Here, we demonstrate strong coherent coupling...

  10. Description of quantum states using in free space optic communication

    Science.gov (United States)

    Kučera, Petr

    2017-11-01

    In the article we concentrate our attention on the quantum description of states which are prepared by light sources. The main goal of the article is the determination of density matrix of background radiation source. It is shown that these matrix elements satisfy Geometric distribution in the number state representation.

  11. Analysis of limiting information characteristics of quantum-cryptography protocols

    International Nuclear Information System (INIS)

    Sych, D V; Grishanin, Boris A; Zadkov, Viktor N

    2005-01-01

    The problem of increasing the critical error rate of quantum-cryptography protocols by varying a set of letters in a quantum alphabet for space of a fixed dimensionality is studied. Quantum alphabets forming regular polyhedra on the Bloch sphere and the continual alphabet equally including all the quantum states are considered. It is shown that, in the absence of basis reconciliation, a protocol with the tetrahedral alphabet has the highest critical error rate among the protocols considered, while after the basis reconciliation, a protocol with the continual alphabet possesses the highest critical error rate. (quantum optics and quantum computation)

  12. Quantum teleportation and entanglement distribution over 100-kilometre free-space channels.

    Science.gov (United States)

    Yin, Juan; Ren, Ji-Gang; Lu, He; Cao, Yuan; Yong, Hai-Lin; Wu, Yu-Ping; Liu, Chang; Liao, Sheng-Kai; Zhou, Fei; Jiang, Yan; Cai, Xin-Dong; Xu, Ping; Pan, Ge-Sheng; Jia, Jian-Jun; Huang, Yong-Mei; Yin, Hao; Wang, Jian-Yu; Chen, Yu-Ao; Peng, Cheng-Zhi; Pan, Jian-Wei

    2012-08-09

    Transferring an unknown quantum state over arbitrary distances is essential for large-scale quantum communication and distributed quantum networks. It can be achieved with the help of long-distance quantum teleportation and entanglement distribution. The latter is also important for fundamental tests of the laws of quantum mechanics. Although quantum teleportation and entanglement distribution over moderate distances have been realized using optical fibre links, the huge photon loss and decoherence in fibres necessitate the use of quantum repeaters for larger distances. However, the practical realization of quantum repeaters remains experimentally challenging. Free-space channels, first used for quantum key distribution, offer a more promising approach because photon loss and decoherence are almost negligible in the atmosphere. Furthermore, by using satellites, ultra-long-distance quantum communication and tests of quantum foundations could be achieved on a global scale. Previous experiments have achieved free-space distribution of entangled photon pairs over distances of 600 metres (ref. 14) and 13 kilometres (ref. 15), and transfer of triggered single photons over a 144-kilometre one-link free-space channel. Most recently, following a modified scheme, free-space quantum teleportation over 16 kilometres was demonstrated with a single pair of entangled photons. Here we report quantum teleportation of independent qubits over a 97-kilometre one-link free-space channel with multi-photon entanglement. An average fidelity of 80.4 ± 0.9 per cent is achieved for six distinct states. Furthermore, we demonstrate entanglement distribution over a two-link channel, in which the entangled photons are separated by 101.8 kilometres. Violation of the Clauser-Horne-Shimony-Holt inequality is observed without the locality loophole. Besides being of fundamental interest, our results represent an important step towards a global quantum network. Moreover, the high

  13. A Generic Simulation Framework for Non-Entangled based Experimental Quantum Cryptography and Communication: Quantum Cryptography and Communication Simulator (QuCCs)

    Science.gov (United States)

    Buhari, Abudhahir; Zukarnain, Zuriati Ahmad; Khalid, Roszelinda; Zakir Dato', Wira Jaafar Ahmad

    2016-11-01

    The applications of quantum information science move towards bigger and better heights for the next generation technology. Especially, in the field of quantum cryptography and quantum computation, the world already witnessed various ground-breaking tangible product and promising results. Quantum cryptography is one of the mature field from quantum mechanics and already available in the markets. The current state of quantum cryptography is still under various researches in order to reach the heights of digital cryptography. The complexity of quantum cryptography is higher due to combination of hardware and software. The lack of effective simulation tool to design and analyze the quantum cryptography experiments delays the reaching distance of the success. In this paper, we propose a framework to achieve an effective non-entanglement based quantum cryptography simulation tool. We applied hybrid simulation technique i.e. discrete event, continuous event and system dynamics. We also highlight the limitations of a commercial photonic simulation tool based experiments. Finally, we discuss ideas for achieving one-stop simulation package for quantum based secure key distribution experiments. All the modules of simulation framework are viewed from the computer science perspective.

  14. Principles of the new quantum cryptography protocols building

    International Nuclear Information System (INIS)

    Kurochkin, V.; Kurochkin, Yu.

    2009-01-01

    The main aim of the quantum cryptography protocols is the maximal secrecy under the conditions of the real experiment. This work presents the result of the new protocol building with the use of the secrecy maximization. While using some well-known approaches this method has allowed one to achieve completely new results in quantum cryptography. The process of the protocol elaboration develops from the standard BB84 protocol upgrading to the building of completely new protocol with arbitrary large bases number. The secrecy proofs of the elaborated protocol appear to be natural continuation of the protocol building process. This approach reveals possibility to reach extremely high parameters of the protocol. It suits both the restrictions of contemporary technologies and requirements for high bit rate while being absolutely secret

  15. Nonlinear laser dynamics from quantum dots to cryptography

    CERN Document Server

    Lüdge, Kathy

    2012-01-01

    A distinctive discussion of the nonlinear dynamical phenomena of semiconductor lasers. The book combines recent results of quantum dot laser modeling with mathematical details and an analytic understanding of nonlinear phenomena in semiconductor lasers and points out possible applications of lasers in cryptography and chaos control. This interdisciplinary approach makes it a unique and powerful source of knowledge for anyone intending to contribute to this field of research.By presenting both experimental and theoretical results, the distinguished authors consider solitary lase

  16. Post-Quantum Cryptography: Riemann Primitives and Chrysalis

    OpenAIRE

    Malloy, Ian; Hollenbeck, Dennis

    2018-01-01

    The Chrysalis project is a proposed method for post-quantum cryptography using the Riemann sphere. To this end, Riemann primitives are introduced in addition to a novel implementation of this new method. Chrysalis itself is the first cryptographic scheme to rely on Holomorphic Learning with Errors, which is a complex form of Learning with Errors relying on the Gauss Circle Problem within the Riemann sphere. The principle security reduction proposed by this novel cryptographic scheme applies c...

  17. Daylight operation of a free space, entanglement-based quantum key distribution system

    Energy Technology Data Exchange (ETDEWEB)

    Peloso, Matthew P; Gerhardt, Ilja; Ho, Caleb; Lamas-Linares, AntIa; Kurtsiefer, Christian [Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 (Singapore)], E-mail: christian.kurtsiefer@gmail.com

    2009-04-15

    Many quantum key distribution (QKD) implementations using a free space transmission path are restricted to operation at night time in order to distinguish the signal photons used for a secure key establishment from the background light. Here, we present a lean entanglement-based QKD system overcoming that limitation. By implementing spectral, spatial and temporal filtering techniques, we establish a secure key continuously over several days under varying light and weather conditions.

  18. Cryptography from quantum uncertainty in the presence of quantum side information

    NARCIS (Netherlands)

    Bouman, Niek Johannes

    2012-01-01

    The thesis starts with a high-level introduction into cryptography and quantum mechanics. Chapter 2 gives a theoretical foundation by introducing probability theory, information theory, functional analysis, quantum mechanics and quantum information theory. Chapter 3, 4 and 5 are editions of work

  19. Quantum cryptography as a retrodiction problem.

    Science.gov (United States)

    Werner, A H; Franz, T; Werner, R F

    2009-11-27

    We propose a quantum key distribution protocol based on a quantum retrodiction protocol, known as the Mean King problem. The protocol uses a two way quantum channel. We show security against coherent attacks in a transmission-error free scenario, even if Eve is allowed to attack both transmissions. This establishes a connection between retrodiction and key distribution.

  20. An Online Banking System Based on Quantum Cryptography Communication

    Science.gov (United States)

    Zhou, Ri-gui; Li, Wei; Huan, Tian-tian; Shen, Chen-yi; Li, Hai-sheng

    2014-07-01

    In this paper, an online banking system has been built. Based on quantum cryptography communication, this system is proved unconditional secure. Two sets of GHZ states are applied, which can ensure the safety of purchase and payment, respectively. In another word, three trading participants in each triplet state group form an interdependent and interactive relationship. In the meantime, trading authorization and blind signature is introduced by means of controllable quantum teleportation. Thus, an effective monitor is practiced on the premise that the privacy of trading partners is guaranteed. If there is a dispute or deceptive behavior, the system will find out the deceiver immediately according to the relationship mentioned above.

  1. Entanglement witnessing and quantum cryptography with nonideal ferromagnetic detectors

    Science.gov (United States)

    Kłobus, Waldemar; Grudka, Andrzej; Baumgartner, Andreas; Tomaszewski, Damian; Schönenberger, Christian; Martinek, Jan

    2014-03-01

    We investigate theoretically the use of nonideal ferromagnetic contacts as a means to detect quantum entanglement of electron spins in transport experiments. We use a designated entanglement witness and find a minimal spin polarization of η >1/√3 ≈58% required to demonstrate spin entanglement. This is significantly less stringent than the ubiquitous tests of Bell's inequality with η >1/√24 >≈84%. In addition, we discuss the impact of decoherence and noise on entanglement detection and apply the presented framework to a simple quantum cryptography protocol. Our results are directly applicable to a large variety of experiments.

  2. Three-Stage Quantum Cryptography Protocol under Collective-Rotation Noise

    OpenAIRE

    Wu, Linsen; Chen, Yuhua

    2015-01-01

    Information security is increasingly important as society migrates to the information age. Classical cryptography widely used nowadays is based on computational complexity, which means that it assumes that solving some particular mathematical problems is hard on a classical computer. With the development of supercomputers and, potentially, quantum computers, classical cryptography has more and more potential risks. Quantum cryptography provides a solution which is based on the Heisenberg unce...

  3. Free-Space Optical Communications Link at 1550-nm using Multiple-Quantum-Well Modulating Retroreflectors in a Marine Environment

    National Research Council Canada - National Science Library

    Rabinovich, W. S; Mahon, R; Burris, H. R; Gilbreath, G. C; Goetz, P. G; Moore, C. I; Stell, M. F; Vilcheck, M. J; Witkowsky, J. L; Swingen, L

    2005-01-01

    A 1550-nm eye-safe, free-space optical communications link is demonstrated at rates up to 5 Mbits/s over a distance of 2 km in the Chesapeake Bay, using quantum-well-based modulating retroreflectors...

  4. Some conservative estimates in quantum cryptography

    International Nuclear Information System (INIS)

    Molotkov, S. N.

    2006-01-01

    Relationship is established between the security of the BB84 quantum key distribution protocol and the forward and converse coding theorems for quantum communication channels. The upper bound Q c ∼ 11% on the bit error rate compatible with secure key distribution is determined by solving the transcendental equation H(Q c )=C-bar(ρ)/2, where ρ is the density matrix of the input ensemble, C-bar(ρ) is the classical capacity of a noiseless quantum channel, and H(Q) is the capacity of a classical binary symmetric channel with error rate Q

  5. Security of quantum cryptography with realistic sources

    International Nuclear Information System (INIS)

    Lutkenhaus, N.

    1999-01-01

    The interest in practical implementations of quantum key distribution is steadily growing. However, there is still a need to give a precise security statement which adapts to realistic implementation. In this paper I give the effective key rate we can obtain in a practical setting within scenario of security against individual attacks by an eavesdropper. It illustrates previous results that high losses together with detector dark counts can make secure quantum key distribution impossible. (Author)

  6. Security of quantum cryptography with realistic sources

    Energy Technology Data Exchange (ETDEWEB)

    Lutkenhaus, N [Helsinki Institute of Physics, P.O. Box 9, 00014 Helsingin yliopisto (Finland)

    1999-08-01

    The interest in practical implementations of quantum key distribution is steadily growing. However, there is still a need to give a precise security statement which adapts to realistic implementation. In this paper I give the effective key rate we can obtain in a practical setting within scenario of security against individual attacks by an eavesdropper. It illustrates previous results that high losses together with detector dark counts can make secure quantum key distribution impossible. (Author)

  7. Long-distance quantum teleportation assisted with free-space entanglement distribution

    International Nuclear Information System (INIS)

    Ji-Gang, Ren; Zhen-Huan, Yi; Fei, Zhou; Cheng-Zhi, Peng; Jian-Wei, Pan; Bin, Yang; Kai, Chen

    2009-01-01

    Faithful long-distance quantum teleportation necessitates prior entanglement distribution between two communicated locations. The particle carrying on the unknown quantum information is then combined with one particle of the entangled states for Bell-state measurements, which leads to a transfer of the original quantum information onto the other particle of the entangled states. However in most of the implemented teleportation experiments nowadays, the Bell-state measurements are performed even before successful distribution of entanglement. This leads to an instant collapse of the quantum state for the transmitted particle, which is actually a single-particle transmission thereafter. Thus the true distance for quantum teleportation is, in fact, only in a level of meters. In the present experiment we design a novel scheme which has overcome this limit by utilizing fiber as quantum memory. A complete quantum teleportation is achieved upon successful entanglement distribution over 967 meters in public free space. Active feed-forward control techniques are developed for real-time transfer of quantum information. The overall experimental fidelities for teleported states are better than 89.6%, which signify high-quality teleportation. (rapid communications)

  8. Long-distance free-space distribution of quantum entanglement over Vienna

    International Nuclear Information System (INIS)

    Lindenthal, M.; Resch, K.; Blauensteiner, B.; Boehm, H.; Fedrizzi, A.; Kurtsiefer, C.; Poppe, A.; Schmitt-Manderbach, T.; Taraba, M.; Ursin, R.; Walther, P.; Weier, H.; Weinfurter, H.; Zeilinger, A.

    2005-01-01

    Full text: We have established a real-world free-space quantum channel over 7.8 km and demonstrate the distribution of entangled photons. The transmitter is placed at an observatory and the receiver on the 46th floor of an office skyscraper in Vienna, Austria. Using locally recorded time stamps and a public internet channel, coincident counts from correlated photons are demonstrated to violate a Bell inequality by 14 standard deviations. This confirms the high quality of the shared entanglement. In this experiment the horizontal freespace distance is chosen, so that the attenuation the light undergoes corresponds approximately to the attenuation from space to earth. This work is an encouraging step towards satellite-based distribution of quantum entanglement and future intra-city quantum networks. (author)

  9. Finite key analysis in quantum cryptography

    International Nuclear Information System (INIS)

    Meyer, T.

    2007-01-01

    In view of experimental realization of quantum key distribution schemes, the study of their efficiency becomes as important as the proof of their security. The latter is the subject of most of the theoretical work about quantum key distribution, and many important results such as the proof of unconditional security have been obtained. The efficiency and also the robustness of quantum key distribution protocols against noise can be measured by figures of merit such as the secret key rate (the fraction of input signals that make it into the key) and the threshold quantum bit error rate (the maximal error rate such that one can still create a secret key). It is important to determine these quantities because they tell us whether a certain quantum key distribution scheme can be used at all in a given situation and if so, how many secret key bits it can generate in a given time. However, these figures of merit are usually derived under the ''infinite key limit'' assumption, that is, one assumes that an infinite number of quantum states are send and that all sub-protocols of the scheme (in particular privacy amplification) are carried out on these infinitely large blocks. Such an assumption usually eases the analysis, but also leads to (potentially) too optimistic values for the quantities in question. In this thesis, we are explicitly avoiding the infinite key limit for the analysis of the privacy amplification step, which plays the most important role in a quantum key distribution scheme. We still assume that an optimal error correction code is applied and we do not take into account any statistical errors that might occur in the parameter estimation step. Renner and coworkers derived an explicit formula for the obtainable key rate in terms of Renyi entropies of the quantum states describing Alice's, Bob's, and Eve's systems. This results serves as a starting point for our analysis, and we derive an algorithm that efficiently computes the obtainable key rate for any

  10. Deterministic and efficient quantum cryptography based on Bell's theorem

    International Nuclear Information System (INIS)

    Chen Zengbing; Pan Jianwei; Zhang Qiang; Bao Xiaohui; Schmiedmayer, Joerg

    2006-01-01

    We propose a double-entanglement-based quantum cryptography protocol that is both efficient and deterministic. The proposal uses photon pairs with entanglement both in polarization and in time degrees of freedom; each measurement in which both of the two communicating parties register a photon can establish one and only one perfect correlation, and thus deterministically create a key bit. Eavesdropping can be detected by violation of local realism. A variation of the protocol shows a higher security, similar to the six-state protocol, under individual attacks. Our scheme allows a robust implementation under the current technology

  11. One-way entangled-photon autocompensating quantum cryptography

    Science.gov (United States)

    Walton, Zachary D.; Abouraddy, Ayman F.; Sergienko, Alexander V.; Saleh, Bahaa E.; Teich, Malvin C.

    2003-06-01

    A quantum cryptography implementation is presented that uses entanglement to combine one-way operation with an autocompensating feature that has hitherto only been available in implementations that require the signal to make a round trip between the users. Using the concept of advanced waves, it is shown that this proposed implementation is related to the round-trip implementation in the same way that Ekert’s two-particle scheme is related to the original one-particle scheme of Bennett and Brassard. The practical advantages and disadvantages of the proposed implementation are discussed in the context of existing schemes.

  12. One-way entangled-photon autocompensating quantum cryptography

    International Nuclear Information System (INIS)

    Walton, Zachary D.; Abouraddy, Ayman F.; Sergienko, Alexander V.; Saleh, Bahaa E. A.; Teich, Malvin C.

    2003-01-01

    A quantum cryptography implementation is presented that uses entanglement to combine one-way operation with an autocompensating feature that has hitherto only been available in implementations that require the signal to make a round trip between the users. Using the concept of advanced waves, it is shown that this proposed implementation is related to the round-trip implementation in the same way that Ekert's two-particle scheme is related to the original one-particle scheme of Bennett and Brassard. The practical advantages and disadvantages of the proposed implementation are discussed in the context of existing schemes

  13. Deterministic and efficient quantum cryptography based on Bell's theorem

    International Nuclear Information System (INIS)

    Chen, Z.-B.; Zhang, Q.; Bao, X.-H.; Schmiedmayer, J.; Pan, J.-W.

    2005-01-01

    Full text: We propose a novel double-entanglement-based quantum cryptography protocol that is both efficient and deterministic. The proposal uses photon pairs with entanglement both in polarization and in time degrees of freedom; each measurement in which both of the two communicating parties register a photon can establish a key bit with the help of classical communications. Eavesdropping can be detected by checking the violation of local realism for the detected events. We also show that our protocol allows a robust implementation under current technology. (author)

  14. Quantum cryptography with an ideal local relay

    DEFF Research Database (Denmark)

    Spedalieri, Gaetana; Ottaviani, Carlo; Braunstein, Samuel L.

    2015-01-01

    We consider two remote parties connected to a relay by two quantum channels. To generate a secret key, they transmit coherent states to the relay, where the states are subject to a continuous-variable (CV) Bell detection. We study the ideal case where Alice's channel is lossless, i.e., the relay ...

  15. Finite key analysis in quantum cryptography

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, T.

    2007-10-31

    In view of experimental realization of quantum key distribution schemes, the study of their efficiency becomes as important as the proof of their security. The latter is the subject of most of the theoretical work about quantum key distribution, and many important results such as the proof of unconditional security have been obtained. The efficiency and also the robustness of quantum key distribution protocols against noise can be measured by figures of merit such as the secret key rate (the fraction of input signals that make it into the key) and the threshold quantum bit error rate (the maximal error rate such that one can still create a secret key). It is important to determine these quantities because they tell us whether a certain quantum key distribution scheme can be used at all in a given situation and if so, how many secret key bits it can generate in a given time. However, these figures of merit are usually derived under the ''infinite key limit'' assumption, that is, one assumes that an infinite number of quantum states are send and that all sub-protocols of the scheme (in particular privacy amplification) are carried out on these infinitely large blocks. Such an assumption usually eases the analysis, but also leads to (potentially) too optimistic values for the quantities in question. In this thesis, we are explicitly avoiding the infinite key limit for the analysis of the privacy amplification step, which plays the most important role in a quantum key distribution scheme. We still assume that an optimal error correction code is applied and we do not take into account any statistical errors that might occur in the parameter estimation step. Renner and coworkers derived an explicit formula for the obtainable key rate in terms of Renyi entropies of the quantum states describing Alice's, Bob's, and Eve's systems. This results serves as a starting point for our analysis, and we derive an algorithm that efficiently computes

  16. The Singapore protocol [for quantum cryptography

    International Nuclear Information System (INIS)

    Englert, B.

    2005-01-01

    The qubit protocol for quantum key distribution presented in this talk is fully tomographic and more efficient than other tomographic protocols. Under ideal circumstances the efficiency is log 2 (4/3) = 0.415 key bits per qubit sent, which is 25% more than the efficiency of 1/3 = 0.333 for the standard 6-state protocol. One can extract 0.4 key bits per qubit by a simple two-way communication scheme, and can so get close to the information-theoretical limit. The noise thresholds for secure key bit generation in the presence of unbiased noise will be reported and discussed. (author)

  17. Three-Stage Quantum Cryptography Protocol under Collective-Rotation Noise

    Directory of Open Access Journals (Sweden)

    Linsen Wu

    2015-05-01

    Full Text Available Information security is increasingly important as society migrates to the information age. Classical cryptography widely used nowadays is based on computational complexity, which means that it assumes that solving some particular mathematical problems is hard on a classical computer. With the development of supercomputers and, potentially, quantum computers, classical cryptography has more and more potential risks. Quantum cryptography provides a solution which is based on the Heisenberg uncertainty principle and no-cloning theorem. While BB84-based quantum protocols are only secure when a single photon is used in communication, the three-stage quantum protocol is multi-photon tolerant. However, existing analyses assume perfect noiseless channels. In this paper, a multi-photon analysis is performed for the three-stage quantum protocol under the collective-rotation noise model. The analysis provides insights into the impact of the noise level on a three-stage quantum cryptography system.

  18. No information flow using statistical fluctuations and quantum cryptography

    Science.gov (United States)

    Larsson, Jan-Åke

    2004-04-01

    The communication protocol of Home and Whitaker [Phys. Rev. A 67, 022306 (2003)] is examined in some detail, and found to work equally well using a separable state. The protocol is in fact completely classical, based on postselection of suitable experimental runs. The quantum-cryptography protocol proposed in the same publication is also examined, and this protocol uses entanglement, a strictly quantum property of the system. An individual eavesdropping attack on each qubit pair would be detected by the security test proposed in the mentioned paper. However, the key is provided by groups of qubits, and there exists a coherent attack, internal to these groups, that will go unnoticed in that security test. A modified test is proposed here that will ensure security, even against such a coherent attack.

  19. No information flow using statistical fluctuations and quantum cryptography

    International Nuclear Information System (INIS)

    Larsson, Jan-Aake

    2004-01-01

    The communication protocol of Home and Whitaker [Phys. Rev. A 67, 022306 (2003)] is examined in some detail, and found to work equally well using a separable state. The protocol is in fact completely classical, based on postselection of suitable experimental runs. The quantum-cryptography protocol proposed in the same publication is also examined, and this protocol uses entanglement, a strictly quantum property of the system. An individual eavesdropping attack on each qubit pair would be detected by the security test proposed in the mentioned paper. However, the key is provided by groups of qubits, and there exists a coherent attack, internal to these groups, that will go unnoticed in that security test. A modified test is proposed here that will ensure security, even against such a coherent attack

  20. Position-based quantum cryptography over untrusted networks

    International Nuclear Information System (INIS)

    Nadeem, Muhammad

    2014-01-01

    In this article, we propose quantum position verification (QPV) schemes where all the channels are untrusted except the position of the prover and distant reference stations of verifiers. We review and analyze the existing QPV schemes containing some pre-shared data between the prover and verifiers. Most of these schemes are based on non-cryptographic assumptions, i.e. quantum/classical channels between the verifiers are secure. It seems impractical in an environment fully controlled by adversaries and would lead to security compromise in practical implementations. However, our proposed formula for QPV is more robust, secure and according to the standard assumptions of cryptography. Furthermore, once the position of the prover is verified, our schemes establish secret keys in parallel and can be used for authentication and secret communication between the prover and verifiers. (paper)

  1. Tight finite-key analysis for quantum cryptography.

    Science.gov (United States)

    Tomamichel, Marco; Lim, Charles Ci Wen; Gisin, Nicolas; Renner, Renato

    2012-01-17

    Despite enormous theoretical and experimental progress in quantum cryptography, the security of most current implementations of quantum key distribution is still not rigorously established. One significant problem is that the security of the final key strongly depends on the number, M, of signals exchanged between the legitimate parties. Yet, existing security proofs are often only valid asymptotically, for unrealistically large values of M. Another challenge is that most security proofs are very sensitive to small differences between the physical devices used by the protocol and the theoretical model used to describe them. Here we show that these gaps between theory and experiment can be simultaneously overcome by using a recently developed proof technique based on the uncertainty relation for smooth entropies.

  2. Measurement-Device-Independent Quantum Cryptography

    Science.gov (United States)

    Tang, Zhiyuan

    Quantum key distribution (QKD) enables two legitimate parties to share a secret key even in the presence of an eavesdropper. The unconditional security of QKD is based on the fundamental laws of quantum physics. Original security proofs of QKD are based on a few assumptions, e.g., perfect single photon sources and perfect single-photon detectors. However, practical implementations of QKD systems do not fully comply with such assumptions due to technical limitations. The gap between theory and implementations leads to security loopholes in most QKD systems, and several attacks have been launched on sophisticated QKD systems. Particularly, the detectors have been found to be the most vulnerable part of QKD. Much effort has been put to build side-channel-free QKD systems. Solutions such as security patches and device-independent QKD have been proposed. However, the former are normally ad-hoc, and cannot close unidentified loopholes. The latter, while having the advantages of removing all assumptions on devices, is impractical to implement today. Measurement-device-independent QKD (MDI-QKD) turns out to be a promising solution to the security problem of QKD. In MDI-QKD, all security loopholes, including those yet-to-be discovered, have been removed from the detectors, the most critical part in QKD. In this thesis, we investigate issues related to the practical implementation and security of MDI-QKD. We first present a demonstration of polarization-encoding MDI-QKD. Taking finite key effect into account, we achieve a secret key rate of 0.005 bit per second (bps) over 10 km spooled telecom fiber, and a 1600-bit key is distributed. This work, together with other demonstrations, shows the practicality of MDI-QKD. Next we investigate a critical assumption of MDI-QKD: perfect state preparation. We apply the loss-tolerant QKD protocol and adapt it to MDI-QKD to quantify information leakage due to imperfect state preparation. We then present an experimental demonstration of

  3. Quantum information. Teleportation - cryptography - quantum computer; Quanteninformation. Teleportation - Kryptografie - Quantencomputer

    Energy Technology Data Exchange (ETDEWEB)

    Koenneker, Carsten (comp.)

    2012-11-01

    The following topics are dealt with: Reality in the test facility, quantum teleportation, the reality of quanta, interaction-free quantum measurement, rules for quantum computers, quantum computers with ions, spintronics with diamond, the limits of the quantum computers, a view in the future of quantum optics. (HSI)

  4. Demonstration of free-space reference frame independent quantum key distribution

    International Nuclear Information System (INIS)

    Wabnig, J; Bitauld, D; Li, H W; Niskanen, A O; Laing, A; O'Brien, J L

    2013-01-01

    Quantum key distribution (QKD) is moving from research laboratories towards applications. As computing becomes more mobile, cashless as well as cardless payment solutions are introduced. A possible route to increase the security of wireless communications is to incorporate QKD in a mobile device. Handheld devices present a particular challenge as the orientation and the phase of a qubit will depend on device motion. This problem is addressed by the reference frame independent (RFI) QKD scheme. The scheme tolerates an unknown phase between logical states that vary slowly compared to the rate of particle repetition. Here we experimentally demonstrate the feasibility of RFI QKD over a free-space link in a prepare and measure scheme using polarization encoding. We extend the security analysis of the RFI QKD scheme to be able to deal with uncalibrated devices and a finite number of measurements. Together these advances are an important step towards mass production of handheld QKD devices. (paper)

  5. Code-Based Cryptography: New Security Solutions Against a Quantum Adversary

    OpenAIRE

    Sendrier , Nicolas; Tillich , Jean-Pierre

    2016-01-01

    International audience; Cryptography is one of the key tools for providing security in our quickly evolving technological society. An adversary with the ability to use a quantum computer would defeat most of the cryptographic solutions that are deployed today to secure our communications. We do not know when quantum computing will become available, but nevertheless, the cryptographic research community must get ready for it now. Code-based cryptography is among the few cryptographic technique...

  6. Implementation of multiplexing in a subcarrier-wave quantum cryptography system

    International Nuclear Information System (INIS)

    Chistyakov, V V; Gleim, A V; Egorov, V I; Nazarov, Yu V

    2014-01-01

    Quantum cryptography allows distributing secure keys in a way that any eavesdropping in the channel is inevitably detected. This work is dedicated to introducing wavelength division multiplexing in a subcarrier-wave quantum cryptography system. Compared to other existing schemes, the resulting device is able to achieve higher bitrates (up to 2.26 Mbit/s at 20 km), is robust against external conditions and compatible with standard telecommunication fibres in multi-user environment

  7. Quantum foundations in the light of quantum cryptography

    International Nuclear Information System (INIS)

    Brassard, G.; Fuchs, C.A.

    2005-01-01

    Full text: Consider the two great physical theories of the twentieth century: relativity and quantum mechanics. Einstein derived relativity from very simple principles such as: 'The speed of light in empty space is independent of the speed of its source' and 'Physics should appear the same in all inertial reference frames'. By contrast, the foundation of quantum mechanics is built on a set of rather strange, disjointed and ad hoc axioms. Why is that? Must quantum mechanics be inherently less elegant than relativity? Or is it rather that the current axioms of quantum mechanics reflect at best the history that led to its discovery by too many people (compared to one person for relativity), over too long a period of time? The purpose of this talk is to argue that a better foundation for quantum mechanics lies within the teachings of quantum information science. We postulate that the truly fundamental laws of nature concern information, not waves or particles. For example, it has been proven, from the current axioms of quantum mechanics, that 'nature allows for the unconditionally secure transmission of confidential information', but 'nature does not allow for unconditionally secure bit commitment' (these are standard classical cryptographic primitives). We propose to turn the table around, start from these two theorems and possibly a few others, upgrade them as axioms, and ask how much of quantum mechanics they can derive. This provocative talk is meant as an eye-opener: we shall ask far more questions than we shall resolve. (author)

  8. Quantum cryptography using coherent states: Randomized encryption and key generation

    Science.gov (United States)

    Corndorf, Eric

    With the advent of the global optical-telecommunications infrastructure, an increasing number of individuals, companies, and agencies communicate information with one another over public networks or physically-insecure private networks. While the majority of the traffic flowing through these networks requires little or no assurance of secrecy, the same cannot be said for certain communications between banks, between government agencies, within the military, and between corporations. In these arenas, the need to specify some level of secrecy in communications is a high priority. While the current approaches to securing sensitive information (namely the public-key-cryptography infrastructure and deterministic private-key ciphers like AES and 3DES) seem to be cryptographically strong based on empirical evidence, there exist no mathematical proofs of secrecy for any widely deployed cryptosystem. As an example, the ubiquitous public-key cryptosystems infer all of their secrecy from the assumption that factoring of the product of two large primes is necessarily time consuming---something which has not, and perhaps cannot, be proven. Since the 1980s, the possibility of using quantum-mechanical features of light as a physical mechanism for satisfying particular cryptographic objectives has been explored. This research has been fueled by the hopes that cryptosystems based on quantum systems may provide provable levels of secrecy which are at least as valid as quantum mechanics itself. Unfortunately, the most widely considered quantum-cryptographic protocols (BB84 and the Ekert protocol) have serious implementation problems. Specifically, they require quantum-mechanical states which are not readily available, and they rely on unproven relations between intrusion-level detection and the information available to an attacker. As a result, the secrecy level provided by these experimental implementations is entirely unspecified. In an effort to provably satisfy the cryptographic

  9. Topics in quantum cryptography, quantum error correction, and channel simulation

    Science.gov (United States)

    Luo, Zhicheng

    In this thesis, we mainly investigate four different topics: efficiently implementable codes for quantum key expansion [51], quantum error-correcting codes based on privacy amplification [48], private classical capacity of quantum channels [44], and classical channel simulation with quantum side information [49, 50]. For the first topic, we propose an efficiently implementable quantum key expansion protocol, capable of increasing the size of a pre-shared secret key by a constant factor. Previously, the Shor-Preskill proof [64] of the security of the Bennett-Brassard 1984 (BB84) [6] quantum key distribution protocol relied on the theoretical existence of good classical error-correcting codes with the "dual-containing" property. But the explicit and efficiently decodable construction of such codes is unknown. We show that we can lift the dual-containing constraint by employing the non-dual-containing codes with excellent performance and efficient decoding algorithms. For the second topic, we propose a construction of Calderbank-Shor-Steane (CSS) [19, 68] quantum error-correcting codes, which are originally based on pairs of mutually dual-containing classical codes, by combining a classical code with a two-universal hash function. We show, using the results of Renner and Koenig [57], that the communication rates of such codes approach the hashing bound on tensor powers of Pauli channels in the limit of large block-length. For the third topic, we prove a regularized formula for the secret key assisted capacity region of a quantum channel for transmitting private classical information. This result parallels the work of Devetak on entanglement assisted quantum communication capacity. This formula provides a new family protocol, the private father protocol, under the resource inequality framework that includes the private classical communication without the assisted secret keys as a child protocol. For the fourth topic, we study and solve the problem of classical channel

  10. Fast and simple high-capacity quantum cryptography with error detection

    Science.gov (United States)

    Lai, Hong; Luo, Ming-Xing; Pieprzyk, Josef; Zhang, Jun; Pan, Lei; Li, Shudong; Orgun, Mehmet A.

    2017-04-01

    Quantum cryptography is commonly used to generate fresh secure keys with quantum signal transmission for instant use between two parties. However, research shows that the relatively low key generation rate hinders its practical use where a symmetric cryptography component consumes the shared key. That is, the security of the symmetric cryptography demands frequent rate of key updates, which leads to a higher consumption of the internal one-time-pad communication bandwidth, since it requires the length of the key to be as long as that of the secret. In order to alleviate these issues, we develop a matrix algorithm for fast and simple high-capacity quantum cryptography. Our scheme can achieve secure private communication with fresh keys generated from Fibonacci- and Lucas- valued orbital angular momentum (OAM) states for the seed to construct recursive Fibonacci and Lucas matrices. Moreover, the proposed matrix algorithm for quantum cryptography can ultimately be simplified to matrix multiplication, which is implemented and optimized in modern computers. Most importantly, considerably information capacity can be improved effectively and efficiently by the recursive property of Fibonacci and Lucas matrices, thereby avoiding the restriction of physical conditions, such as the communication bandwidth.

  11. Fast and simple high-capacity quantum cryptography with error detection.

    Science.gov (United States)

    Lai, Hong; Luo, Ming-Xing; Pieprzyk, Josef; Zhang, Jun; Pan, Lei; Li, Shudong; Orgun, Mehmet A

    2017-04-13

    Quantum cryptography is commonly used to generate fresh secure keys with quantum signal transmission for instant use between two parties. However, research shows that the relatively low key generation rate hinders its practical use where a symmetric cryptography component consumes the shared key. That is, the security of the symmetric cryptography demands frequent rate of key updates, which leads to a higher consumption of the internal one-time-pad communication bandwidth, since it requires the length of the key to be as long as that of the secret. In order to alleviate these issues, we develop a matrix algorithm for fast and simple high-capacity quantum cryptography. Our scheme can achieve secure private communication with fresh keys generated from Fibonacci- and Lucas- valued orbital angular momentum (OAM) states for the seed to construct recursive Fibonacci and Lucas matrices. Moreover, the proposed matrix algorithm for quantum cryptography can ultimately be simplified to matrix multiplication, which is implemented and optimized in modern computers. Most importantly, considerably information capacity can be improved effectively and efficiently by the recursive property of Fibonacci and Lucas matrices, thereby avoiding the restriction of physical conditions, such as the communication bandwidth.

  12. Security proof of counterfactual quantum cryptography against general intercept-resend attacks and its vulnerability

    International Nuclear Information System (INIS)

    Zhang Sheng; Wang Jian; Tang Chao-Jing

    2012-01-01

    Counterfactual quantum cryptography, recently proposed by Noh, is featured with no transmission of signal particles. This exhibits evident security advantages, such as its immunity to the well-known photon-number-splitting attack. In this paper, the theoretical security of counterfactual quantum cryptography protocol against the general intercept-resend attacks is proved by bounding the information of an eavesdropper Eve more tightly than in Yin's proposal [Phys. Rev. A 82 042335 (2010)]. It is also shown that practical counterfactual quantum cryptography implementations may be vulnerable when equipped with imperfect apparatuses, by proving that a negative key rate can be achieved when Eve launches a time-shift attack based on imperfect detector efficiency. (general)

  13. Security improvement by using a modified coherent state for quantum cryptography

    International Nuclear Information System (INIS)

    Lu, Y.J.; Zhu, Luobei; Ou, Z.Y.

    2005-01-01

    Weak coherent states as a photon source for quantum cryptography have a limit in secure data rate and transmission distance because of the presence of multiphoton events and loss in transmission line. Two-photon events in a coherent state can be taken out by a two-photon interference scheme. We investigate the security issue of utilizing this modified coherent state in quantum cryptography. A 4-dB improvement in the secure data rate or a nearly twofold increase in transmission distance over the coherent state are found. With a recently proposed and improved encoding strategy, further improvement is possible

  14. Decoy state method for quantum cryptography based on phase coding into faint laser pulses

    Science.gov (United States)

    Kulik, S. P.; Molotkov, S. N.

    2017-12-01

    We discuss the photon number splitting attack (PNS) in systems of quantum cryptography with phase coding. It is shown that this attack, as well as the structural equations for the PNS attack for phase encoding, differs physically from the analogous attack applied to the polarization coding. As far as we know, in practice, in all works to date processing of experimental data has been done for phase coding, but using formulas for polarization coding. This can lead to inadequate results for the length of the secret key. These calculations are important for the correct interpretation of the results, especially if it concerns the criterion of secrecy in quantum cryptography.

  15. Cryptographic robustness of practical quantum cryptography: BB84 key distribution protocol

    International Nuclear Information System (INIS)

    Molotkov, S. N.

    2008-01-01

    In real fiber-optic quantum cryptography systems, the avalanche photodiodes are not perfect, the source of quantum states is not a single-photon one, and the communication channel is lossy. For these reasons, key distribution is impossible under certain conditions for the system parameters. A simple analysis is performed to find relations between the parameters of real cryptography systems and the length of the quantum channel that guarantee secure quantum key distribution when the eavesdropper's capabilities are limited only by fundamental laws of quantum mechanics while the devices employed by the legitimate users are based on current technologies. Critical values are determined for the rate of secure real-time key generation that can be reached under the current technology level. Calculations show that the upper bound on channel length can be as high as 300 km for imperfect photodetectors (avalanche photodiodes) with present-day quantum efficiency (η ∼ 20%) and dark count probability (p dark ∼ 10 -7 )

  16. Breaking the Unbreakable : Exploiting Loopholes in Bell’s Theorem to Hack Quantum Cryptography

    OpenAIRE

    Jogenfors, Jonathan

    2017-01-01

    In this thesis we study device-independent quantum key distribution based on energy-time entanglement. This is a method for cryptography that promises not only perfect secrecy, but also to be a practical method for quantum key distribution thanks to the reduced complexity when compared to other quantum key distribution protocols. However, there still exist a number of loopholes that must be understood and eliminated in order to rule out eavesdroppers. We study several relevant loopholes and s...

  17. Insecurity of position-based quantum-cryptography protocols against entanglement attacks

    International Nuclear Information System (INIS)

    Lau, Hoi-Kwan; Lo, Hoi-Kwong

    2011-01-01

    Recently, position-based quantum cryptography has been claimed to be unconditionally secure. On the contrary, here we show that the existing proposals for position-based quantum cryptography are, in fact, insecure if entanglement is shared among two adversaries. Specifically, we demonstrate how the adversaries can incorporate ideas of quantum teleportation and quantum secret sharing to compromise the security with certainty. The common flaw to all current protocols is that the Pauli operators always map a codeword to a codeword (up to an irrelevant overall phase). We propose a modified scheme lacking this property in which the same cheating strategy used to undermine the previous protocols can succeed with a rate of at most 85%. We prove the modified protocol is secure when the shared quantum resource between the adversaries is a two- or three-level system.

  18. One-time pad, complexity of verification of keys, and practical security of quantum cryptography

    Energy Technology Data Exchange (ETDEWEB)

    Molotkov, S. N., E-mail: sergei.molotkov@gmail.com [Russian Academy of Sciences, Institute of Solid State Physics (Russian Federation)

    2016-11-15

    A direct relation between the complexity of the complete verification of keys, which is one of the main criteria of security in classical systems, and a trace distance used in quantum cryptography is demonstrated. Bounds for the minimum and maximum numbers of verification steps required to determine the actual key are obtained.

  19. Characterization of collective Gaussian attacks and security of coherent-state quantum cryptography.

    Science.gov (United States)

    Pirandola, Stefano; Braunstein, Samuel L; Lloyd, Seth

    2008-11-14

    We provide a simple description of the most general collective Gaussian attack in continuous-variable quantum cryptography. In the scenario of such general attacks, we analyze the asymptotic secret-key rates which are achievable with coherent states, joint measurements of the quadratures and one-way classical communication.

  20. Quantum cryptography using a photon source based on postselection from entangled two-photon states

    Czech Academy of Sciences Publication Activity Database

    Peřina ml., Jan; Haderka, Ondřej; Soubusta, Jan

    2001-01-01

    Roč. 64, - (2001), s. 052305-1-152305-13 ISSN 1050-2947 R&D Projects: GA MŠk LN00A015 Institutional research plan: CEZ:AV0Z1010914 Keywords : quantum cryptography * photon number squeezing Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.810, year: 2001

  1. One-time pad, complexity of verification of keys, and practical security of quantum cryptography

    International Nuclear Information System (INIS)

    Molotkov, S. N.

    2016-01-01

    A direct relation between the complexity of the complete verification of keys, which is one of the main criteria of security in classical systems, and a trace distance used in quantum cryptography is demonstrated. Bounds for the minimum and maximum numbers of verification steps required to determine the actual key are obtained.

  2. Quantum-tomographic cryptography with a semiconductor single-photon source

    International Nuclear Information System (INIS)

    Kaszlikowski, D.; Yang, L.J.; Yong, L.S.; Willeboordse, F.H.; Kwek, L.C.

    2005-01-01

    We analyze the security of so-called quantum-tomographic cryptography with the source producing entangled photons via an experimental scheme proposed by Fattal et al. [Phys. Rev. Lett. 92, 37903 (2004)]. We determine the range of the experimental parameters for which the protocol is secure against the most general incoherent attacks

  3. Comment on 'Two-way protocols for quantum cryptography with a nonmaximally entangled qubit pair'

    International Nuclear Information System (INIS)

    Qin Sujuan; Gao Fei; Wen Qiaoyan; Guo Fenzhuo

    2010-01-01

    Three protocols of quantum cryptography with a nonmaximally entangled qubit pair [Phys. Rev. A 80, 022323 (2009)] were recently proposed by Shimizu, Tamaki, and Fukasaka. The security of these protocols is based on the quantum-mechanical constraint for a state transformation between nonmaximally entangled states. However, we find that the second protocol is vulnerable under the correlation-elicitation attack. An eavesdropper can obtain the encoded bit M although she has no knowledge about the random bit R.

  4. Perspectives on Entangled Nuclear Particle Pairs Generation and Manipulation in Quantum Communication and Cryptography Systems

    Directory of Open Access Journals (Sweden)

    Octavian Dănilă

    2012-01-01

    Full Text Available Entanglement between two quantum elements is a phenomenon which presents a broad application spectrum, being used largely in quantum cryptography schemes and in physical characterisation of the universe. Commonly known entangled states have been obtained with photons and electrons, but other quantum elements such as quarks, leptons, and neutrinos have shown their informational potential. In this paper, we present the perspective of exploiting the phenomenon of entanglement that appears in nuclear particle interactions as a resource for quantum key distribution protocols.

  5. Quantum cryptography to satellites for global secure key distribution

    Science.gov (United States)

    Rarity, John G.; Gorman, Philip M.; Knight, Paul; Wallace, Kotska; Tapster, Paul R.

    2017-11-01

    We have designed and built a free space secure key exchange system using weak laser pulses with polarisation modulation by acousto-optic switching. We have used this system to exchange keys over a 1.2km ground range with absolute security. Building from this initial result we analyse the feasibility of exchanging keys to a low earth orbit satellite.

  6. Polarization tracking system for free-space optical communication, including quantum communication

    Science.gov (United States)

    Nordholt, Jane Elizabeth; Newell, Raymond Thorson; Peterson, Charles Glen; Hughes, Richard John

    2018-01-09

    Quantum communication transmitters include beacon lasers that transmit a beacon optical signal in a predetermined state of polarization such as one of the states of polarization of a quantum communication basis. Changes in the beacon polarization are detected at a receiver, and a retarder is adjusted so that the states of polarization in a received quantum communication optical signal are matched to basis polarizations. The beacon and QC signals can be at different wavelengths so that the beacon does not interfere with detection and decoding of the QC optical signal.

  7. Femtosecond Laser--Pumped Source of Entangled Photons for Quantum Cryptography Applications

    International Nuclear Information System (INIS)

    Pan, D.; Donaldson, W.; Sobolewski, R.

    2007-01-01

    We present an experimental setup for generation of entangled-photon pairs via spontaneous parametric down-conversion, based on the femtosecond-pulsed laser. Our entangled-photon source utilizes a 76-MHz-repetition-rate, 100-fs-pulse-width, mode-locked, ultrafast femtosecond laser, which can produce, on average, more photon pairs than a cw laser of an equal pump power. The resulting entangled pairs are counted by a pair of high-quantum-efficiency, single-photon, silicon avalanche photodiodes. Our apparatus s intended as an efficient source/receiver system for the quantum communications and quantum cryptography applications

  8. A Novel Basis Splitting Eavesdropping Scheme in Quantum Cryptography Based on the BB84 Protocol

    International Nuclear Information System (INIS)

    Zhao Nan; Zhu Chang-Hua; Quan Dong-Xiao

    2015-01-01

    We propose a novel strategy named basis-splitting scheme to split the intercepted quanta into several portions based on different bases, for eavesdropping in the process of quantum cryptography. Compared with intercept-resend strategy, our simulation results of the basis-splitting scheme under the non-ideal condition show a greater performance, especially with the increase of the length of shifted bits. Consequently our scheme can aid eavesdropper to gather much more useful information. (paper)

  9. A photonic nanowire trumpet for interfacing a quantum dot and a Gaussian free-space mode

    DEFF Research Database (Denmark)

    Gregersen, Niels; Munsch, Mathieu; Malik, Nitin S.

    2013-01-01

    Efficient coupling between a localized quantum emitter and a well defined optical channel represents a powerful route to realize single-photon sources and spin-photon interfaces. The tailored fiber-like photonic nanowire embedding a single quantum dot has recently demonstrated an appealing...... potential. However, the device requires a delicate, sharp needle-like taper with performance sensitive to minute geometrical details. To overcome this limitation we demonstrate the photonic trumpet, exploiting an opposite tapering strategy. The trumpet features a strongly Gaussian far-field emission...

  10. Is long distance free space quantum communication with the OAM state of light feasible [Presentation

    CSIR Research Space (South Africa)

    Hamadou Ibrahim, A

    2013-06-01

    Full Text Available -space quantum communication with the OAM state of light feasible? A. HAMADOU IBRAHIM1,2, F.S. ROUX1, M. McLAREN1,3 , A. FORBES1,2,3 & T. KONRAD2 1. CSIR National Laser Centre, PO Box 395, Pretoria 0001 2. School of Physics, University of Kwazulu...

  11. Field test of a practical secure communication network with decoy-state quantum cryptography.

    Science.gov (United States)

    Chen, Teng-Yun; Liang, Hao; Liu, Yang; Cai, Wen-Qi; Ju, Lei; Liu, Wei-Yue; Wang, Jian; Yin, Hao; Chen, Kai; Chen, Zeng-Bing; Peng, Cheng-Zhi; Pan, Jian-Wei

    2009-04-13

    We present a secure network communication system that operated with decoy-state quantum cryptography in a real-world application scenario. The full key exchange and application protocols were performed in real time among three nodes, in which two adjacent nodes were connected by approximate 20 km of commercial telecom optical fiber. The generated quantum keys were immediately employed and demonstrated for communication applications, including unbreakable real-time voice telephone between any two of the three communication nodes, or a broadcast from one node to the other two nodes by using one-time pad encryption.

  12. Reduced randomness in quantum cryptography with sequences of qubits encoded in the same basis

    International Nuclear Information System (INIS)

    Lamoureux, L.-P.; Cerf, N. J.; Bechmann-Pasquinucci, H.; Gisin, N.; Macchiavello, C.

    2006-01-01

    We consider the cloning of sequences of qubits prepared in the states used in the BB84 or six-state quantum cryptography protocol, and show that the single-qubit fidelity is unaffected even if entire sequences of qubits are prepared in the same basis. This result is only valid provided that the sequences are much shorter than the total key. It is of great importance for practical quantum cryptosystems because it reduces the need for high-speed random number generation without impairing on the security against finite-size cloning attacks

  13. Cryptography In The Bounded Quantum-Storage Model

    DEFF Research Database (Denmark)

    Damgård, Ivan Bjerre; Salvail, Louis; Schaffner, Christian

    2005-01-01

    We initiate the study of two-party cryptographic primitives with unconditional security, assuming that the adversary's quantum memory is of bounded size. We show that oblivious transfer and bit commitment can be implemented in this model using protocols where honest parties need no quantum memory...

  14. Cryptography in the Bounded Quantum-Storage Model

    DEFF Research Database (Denmark)

    Damgård, Ivan Bjerre; Serge, Fehr; Schaffner, Christian

    2008-01-01

    We initiate the study of two-party cryptographic primitives with unconditional security, assuming that the adversary's quantum memory is of bounded size. We show that oblivious transfer and bit commitment can be implemented in this model using protocols where honest parties need no quantum memory...

  15. Quantum cryptography: Theoretical protocols for quantum key distribution and tests of selected commercial QKD systems in commercial fiber networks

    Science.gov (United States)

    Jacak, Monika; Jacak, Janusz; Jóźwiak, Piotr; Jóźwiak, Ireneusz

    2016-06-01

    The overview of the current status of quantum cryptography is given in regard to quantum key distribution (QKD) protocols, implemented both on nonentangled and entangled flying qubits. Two commercial R&D platforms of QKD systems are described (the Clavis II platform by idQuantique implemented on nonentangled photons and the EPR S405 Quelle platform by AIT based on entangled photons) and tested for feasibility of their usage in commercial TELECOM fiber metropolitan networks. The comparison of systems efficiency, stability and resistivity against noise and hacker attacks is given with some suggestion toward system improvement, along with assessment of two models of QKD.

  16. Free-Space Quantum Key Distribution with a High Generation Rate Potassium Titanyl Phosphate Waveguide Photon-Pair Source

    Science.gov (United States)

    Wilson, Jeffrey D.; Chaffee, Dalton W.; Wilson, Nathaniel C.; Lekki, John D.; Tokars, Roger P.; Pouch, John J.; Roberts, Tony D.; Battle, Philip; Floyd, Bertram M.; Lind, Alexander J.; hide

    2016-01-01

    A high generation rate photon-pair source using a dual element periodically-poled potassium titanyl phosphate (PP KTP) waveguide is described. The fully integrated photon-pair source consists of a 1064-nanometer pump diode laser, fiber-coupled to a dual element waveguide within which a pair of 1064-nanometer photons are up-converted to a single 532-nanometer photon in the first stage. In the second stage, the 532-nanometer photon is down-converted to an entangled photon-pair at 800 nanometer and 1600 nanometer which are fiber-coupled at the waveguide output. The photon-pair source features a high pair generation rate, a compact power-efficient package, and continuous wave (CW) or pulsed operation. This is a significant step towards the long term goal of developing sources for high-rate Quantum Key Distribution (QKD) to enable Earth-space secure communications. Characterization and test results are presented. Details and preliminary results of a laboratory free-space QKD experiment with the B92 protocol are also presented.

  17. Free-space measurement-device-independent quantum-key-distribution protocol using decoy states with orbital angular momentum

    International Nuclear Information System (INIS)

    Wang Le; Zhao Sheng-Mei; Cheng Wei-Wen; Gong Long-Yan

    2015-01-01

    In this paper, we propose a measurement-device-independent quantum-key-distribution (MDI-QKD) protocol using orbital angular momentum (OAM) in free space links, named the OAM-MDI-QKD protocol. In the proposed protocol, the OAM states of photons, instead of polarization states, are used as the information carriers to avoid the reference frame alignment, the decoy-state is adopted to overcome the security loophole caused by the weak coherent pulse source, and the high efficient OAM-sorter is adopted as the measurement tool for Charlie to obtain the output OAM state. Here, Charlie may be an untrusted third party. The results show that the authorized users, Alice and Bob, could distill a secret key with Charlie’s successful measurements, and the key generation performance is slightly better than that of the polarization-based MDI-QKD protocol in the two-dimensional OAM cases. Simultaneously, Alice and Bob can reduce the number of flipping the bits in the secure key distillation. It is indicated that a higher key generation rate performance could be obtained by a high dimensional OAM-MDI-QKD protocol because of the unlimited degree of freedom on OAM states. Moreover, the results show that the key generation rate and the transmission distance will decrease as the growth of the strength of atmospheric turbulence (AT) and the link attenuation. In addition, the decoy states used in the proposed protocol can get a considerable good performance without the need for an ideal source. (paper)

  18. A Narrow-Linewidth Atomic Line Filter for Free Space Quantum Key Distribution under Daytime Atmospheric Conditions

    Science.gov (United States)

    Brown, Justin; Woolf, David; Hensley, Joel

    2016-05-01

    Quantum key distribution can provide secure optical data links using the established BB84 protocol, though solar backgrounds severely limit the performance through free space. Several approaches to reduce the solar background include time-gating the photon signal, limiting the field of view through geometrical design of the optical system, and spectral rejection using interference filters. Despite optimization of these parameters, the solar background continues to dominate under daytime atmospheric conditions. We demonstrate an improved spectral filter by replacing the interference filter (Δν ~ 50 GHz) with an atomic line filter (Δν ~ 1 GHz) based on optical rotation of linearly polarized light through a warm Rb vapor. By controlling the magnetic field and the optical depth of the vapor, a spectrally narrow region can be transmitted between crossed polarizers. We find that the transmission is more complex than a single peak and evaluate peak transmission as well as a ratio of peak transmission to average transmission of the local spectrum. We compare filters containing a natural abundance of Rb with those containing isotopically pure 87 Rb and 85 Rb. A filter providing > 95 % transmission and Δν ~ 1.1 GHz is achieved.

  19. Hacking commercial quantum cryptography systems by tailored bright illumination

    Science.gov (United States)

    Lydersen, Lars; Wiechers, Carlos; Wittmann, Christoffer; Elser, Dominique; Skaar, Johannes; Makarov, Vadim

    2010-10-01

    The peculiar properties of quantum mechanics allow two remote parties to communicate a private, secret key, which is protected from eavesdropping by the laws of physics. So-called quantum key distribution (QKD) implementations always rely on detectors to measure the relevant quantum property of single photons. Here we demonstrate experimentally that the detectors in two commercially available QKD systems can be fully remote-controlled using specially tailored bright illumination. This makes it possible to tracelessly acquire the full secret key; we propose an eavesdropping apparatus built from off-the-shelf components. The loophole is likely to be present in most QKD systems using avalanche photodiodes to detect single photons. We believe that our findings are crucial for strengthening the security of practical QKD, by identifying and patching technological deficiencies.

  20. Quantum Cryptography Based on the Deutsch-Jozsa Algorithm

    Science.gov (United States)

    Nagata, Koji; Nakamura, Tadao; Farouk, Ahmed

    2017-09-01

    Recently, secure quantum key distribution based on Deutsch's algorithm using the Bell state is reported (Nagata and Nakamura, Int. J. Theor. Phys. doi: 10.1007/s10773-017-3352-4, 2017). Our aim is of extending the result to a multipartite system. In this paper, we propose a highly speedy key distribution protocol. We present sequre quantum key distribution based on a special Deutsch-Jozsa algorithm using Greenberger-Horne-Zeilinger states. Bob has promised to use a function f which is of one of two kinds; either the value of f( x) is constant for all values of x, or else the value of f( x) is balanced, that is, equal to 1 for exactly half of the possible x, and 0 for the other half. Here, we introduce an additional condition to the function when it is balanced. Our quantum key distribution overcomes a classical counterpart by a factor O(2 N ).

  1. Invisible transmission in quantum cryptography using continuous variables: A proof of Eve's vulnerability

    International Nuclear Information System (INIS)

    Navez, Patrick; Gatti, Alessandra; Lugiato, Luigi A.

    2002-01-01

    By analogy to classical cryptography, we develop a quantum cryptographic scheme in which the two public and private keys consist in each of two entangled beams of squeezed light. An analog secret information is encrypted by modulating the phase of the beam sent in public. The knowledge of the degree of nonclassical correlation between the beam quadratures measured in private and in public allows only the receiver to decrypt the secret information. Finally, in a view towards absolute security, we formally prove that any external intervention of an eavesdropper makes him vulnerable to any subsequent detection

  2. Quantum cryptography with a predetermined key, using continuous-variable Einstein-Podolsky-Rosen correlations

    Science.gov (United States)

    Reid, M. D.

    2000-12-01

    Correlations of the type discussed by EPR in their original 1935 paradox for continuous variables exist for the quadrature phase amplitudes of two spatially separated fields. These correlations were first experimentally reported in 1992. We propose to use such EPR beams in quantum cryptography, to transmit with high efficiency messages in such a way that the receiver and sender may later determine whether eavesdropping has occurred. The merit of the new proposal is in the possibility of transmitting a reasonably secure yet predetermined key. This would allow relay of a cryptographic key over long distances in the presence of lossy channels.

  3. General Theory of Decoy-State Quantum Cryptography with Dark Count Rate Fluctuation

    International Nuclear Information System (INIS)

    Xiang, Gao; Shi-Hai, Sun; Lin-Mei, Liang

    2009-01-01

    The existing theory of decoy-state quantum cryptography assumes that the dark count rate is a constant, but in practice there exists fluctuation. We develop a new scheme of the decoy state, achieve a more practical key generation rate in the presence of fluctuation of the dark count rate, and compare the result with the result of the decoy-state without fluctuation. It is found that the key generation rate and maximal secure distance will be decreased under the influence of the fluctuation of the dark count rate

  4. Gaps between equations and experiments in quantum cryptography

    International Nuclear Information System (INIS)

    Myers, John M; Madjid, F Hadi

    2002-01-01

    Traditional methods of cryptographic key distribution rest on judgments about an attacker. With the advent of quantum key distribution (QKD) came proofs of security for the mathematical models that define the protocols BB84 and B92; however, applying such proofs to actual transmitting and receiving devices has been questioned. Proofs of QKD security are propositions about models written in the mathematical language of quantum mechanics, and the issue is the linking of such models to actual devices in an experiment on security. To explore this issue, we adapt Wittgenstein's method of language games to view quantum language in its application to experimental activity involving transmitting and receiving devices. We sketch concepts with which to think about models in relation to experiments, without assuming the experiments accord with any model; included is a concept of one quantum mechanical model enveloping another. For any model that agrees with given experimental results and implies the security of a key, there is an enveloping model that agrees with the same results while denying that security. As a result there is a gap between equations and the behaviour recorded from devices in an experiment, a gap bridged only by resort to something beyond the reach of logic and measured data, well named by the word guesswork. While this recognition of guesswork encourages eavesdropping, a related recognition of guesswork in the design of feedback loops can help a transmitter and receiver to reduce their vulnerability to eavesdropping

  5. Optimality of Gaussian attacks in continuous-variable quantum cryptography.

    Science.gov (United States)

    Navascués, Miguel; Grosshans, Frédéric; Acín, Antonio

    2006-11-10

    We analyze the asymptotic security of the family of Gaussian modulated quantum key distribution protocols for continuous-variables systems. We prove that the Gaussian unitary attack is optimal for all the considered bounds on the key rate when the first and second momenta of the canonical variables involved are known by the honest parties.

  6. Gaps between equations and experiments in quantum cryptography

    Energy Technology Data Exchange (ETDEWEB)

    Myers, John M [Gordon McKay Laboratory, Division of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138 (United States); Madjid, F Hadi [82 Powers Road, Concord, MA 01742 (United States)

    2002-06-01

    Traditional methods of cryptographic key distribution rest on judgments about an attacker. With the advent of quantum key distribution (QKD) came proofs of security for the mathematical models that define the protocols BB84 and B92; however, applying such proofs to actual transmitting and receiving devices has been questioned. Proofs of QKD security are propositions about models written in the mathematical language of quantum mechanics, and the issue is the linking of such models to actual devices in an experiment on security. To explore this issue, we adapt Wittgenstein's method of language games to view quantum language in its application to experimental activity involving transmitting and receiving devices. We sketch concepts with which to think about models in relation to experiments, without assuming the experiments accord with any model; included is a concept of one quantum mechanical model enveloping another. For any model that agrees with given experimental results and implies the security of a key, there is an enveloping model that agrees with the same results while denying that security. As a result there is a gap between equations and the behaviour recorded from devices in an experiment, a gap bridged only by resort to something beyond the reach of logic and measured data, well named by the word guesswork. While this recognition of guesswork encourages eavesdropping, a related recognition of guesswork in the design of feedback loops can help a transmitter and receiver to reduce their vulnerability to eavesdropping.

  7. Full-field implementation of a perfect eavesdropper on a quantum cryptography system.

    Science.gov (United States)

    Gerhardt, Ilja; Liu, Qin; Lamas-Linares, Antía; Skaar, Johannes; Kurtsiefer, Christian; Makarov, Vadim

    2011-06-14

    Quantum key distribution (QKD) allows two remote parties to grow a shared secret key. Its security is founded on the principles of quantum mechanics, but in reality it significantly relies on the physical implementation. Technological imperfections of QKD systems have been previously explored, but no attack on an established QKD connection has been realized so far. Here we show the first full-field implementation of a complete attack on a running QKD connection. An installed eavesdropper obtains the entire 'secret' key, while none of the parameters monitored by the legitimate parties indicate a security breach. This confirms that non-idealities in physical implementations of QKD can be fully practically exploitable, and must be given increased scrutiny if quantum cryptography is to become highly secure.

  8. Thermal blinding of gated detectors in quantum cryptography.

    Science.gov (United States)

    Lydersen, Lars; Wiechers, Carlos; Wittmann, Christoffer; Elser, Dominique; Skaar, Johannes; Makarov, Vadim

    2010-12-20

    It has previously been shown that the gated detectors of two commercially available quantum key distribution (QKD) systems are blindable and controllable by an eavesdropper using continuous-wave illumination and short bright trigger pulses, manipulating voltages in the circuit [Nat. Photonics 4, 686 (2010)]. This allows for an attack eavesdropping the full raw and secret key without increasing the quantum bit error rate (QBER). Here we show how thermal effects in detectors under bright illumination can lead to the same outcome. We demonstrate that the detectors in a commercial QKD system Clavis2 can be blinded by heating the avalanche photo diodes (APDs) using bright illumination, so-called thermal blinding. Further, the detectors can be triggered using short bright pulses once they are blind. For systems with pauses between packet transmission such as the plug-and-play systems, thermal inertia enables Eve to apply the bright blinding illumination before eavesdropping, making her more difficult to catch.

  9. A sessional blind signature based on quantum cryptography

    Science.gov (United States)

    Khodambashi, Siavash; Zakerolhosseini, Ali

    2014-01-01

    In this paper, we present a sessional blind signature protocol whose security is guaranteed by fundamental principles of quantum physics. It allows a message owner to get his message signed by an authorized signatory. However, the signatory is not capable of reading the message contents and everyone can verify authenticity of the message. For this purpose, we took advantage of a sessional signature as well as quantum entangled pairs which are generated with respect to it in our proposed protocol. We describe our proposed blind signature through an example and briefly discuss about its unconditional security. Due to the feasibility of the protocol, it can be widely employed for e-payment, e-government, e-business and etc.

  10. High-Rate Strong-Signal Quantum Cryptography

    Science.gov (United States)

    Yuen, Horace P.

    1996-01-01

    Several quantum cryptosystems utilizing different kinds of nonclassical lights, which can accommodate high intensity fields and high data rate, are described. However, they are all sensitive to loss and both the high rate and the strong-signal character rapidly disappear. A squeezed light homodyne detection scheme is proposed which, with present-day technology, leads to more than two orders of magnitude data rate improvement over other current experimental systems for moderate loss.

  11. Entanglement witnessing and quantum cryptography with nonideal ferromagnetic detectors

    OpenAIRE

    Kłobus, Waldemar; Grudka, Andrzej; Baumgartner, Andreas; Tomaszewski, Damian; Schönenberger, Christian; Martinek, Jan

    2014-01-01

    We investigate theoretically the use of non-ideal ferromagnetic contacts as a mean to detect quantum entanglement of electron spins in transport experiments. We use a designated entanglement witness and find a minimal spin polarization of $\\eta > 1/\\sqrt{3} \\approx 58 %$ required to demonstrate spin entanglement. This is significantly less stringent than the ubiquitous tests of Bell's inequality with $\\eta > 1/\\sqrt[4]{2}\\approx 84%$. In addition, we discuss the impact of decoherence and nois...

  12. Unconditionally secure commitment in position-based quantum cryptography.

    Science.gov (United States)

    Nadeem, Muhammad

    2014-10-27

    A new commitment scheme based on position-verification and non-local quantum correlations is presented here for the first time in literature. The only credential for unconditional security is the position of committer and non-local correlations generated; neither receiver has any pre-shared data with the committer nor does receiver require trusted and authenticated quantum/classical channels between him and the committer. In the proposed scheme, receiver trusts the commitment only if the scheme itself verifies position of the committer and validates her commitment through non-local quantum correlations in a single round. The position-based commitment scheme bounds committer to reveal valid commitment within allocated time and guarantees that the receiver will not be able to get information about commitment unless committer reveals. The scheme works for the commitment of both bits and qubits and is equally secure against committer/receiver as well as against any third party who may have interests in destroying the commitment. Our proposed scheme is unconditionally secure in general and evades Mayers and Lo-Chau attacks in particular.

  13. On lattices, learning with errors, cryptography, and quantum

    International Nuclear Information System (INIS)

    Regev, O.

    2004-01-01

    Full Text:Our main result is a reduction from worst-case lattice problems such as SVP and SIVP to a certain learning problem. This learning problem is a natural extension of the 'learning from parity with error' problem to higher moduli. It can also be viewed as the problem of decoding from a random linear code. This, we believe, gives a strong indication that these problems are hard. Our reduction, however, is quantum. Hence, an efficient solution to the learning problem implies a quantum algorithm for SVP and SIVP. A main open question is whether this reduction can be made classical. Using the main result, we obtain a public-key cryptosystem whose hardness is based on the worst-case quantum hardness of SVP and SIVP. Previous lattice-based public-key cryptosystems such as the one by Ajtai and Dwork were only based on unique-SVP, a special case of SVP. The new cryptosystem is much more efficient than previous cryptosystems: the public key is of size Ο((n 2 ) and encrypting a message increases its size by Ο((n) (in previous cryptosystems these values are Ο((n 4 ) and Ο(n 2 ), respectively)

  14. Intermediate states in quantum cryptography and Bell inequalities

    International Nuclear Information System (INIS)

    Bechmann-Pasquinucci, H.; Gisin, N.

    2003-01-01

    Intermediate states are known from intercept/resend eavesdropping in the Bennett-Brassard 1984 (BB84) quantum cryptographic protocol. But they also play fundamental roles in the optimal eavesdropping strategy on the BB84 protocol and in the CHSH (Clauser-Horne-Shimony-Holt) inequality. We generalize the intermediate states to an arbitrary dimension and consider intercept/resend eavesdropping, optimal eavesdropping on the generalized BB84 protocol and present a generalized Clauser-Horne-Shimony-Holt inequality for two entangled qudits based on these states

  15. Memory attacks on device-independent quantum cryptography.

    Science.gov (United States)

    Barrett, Jonathan; Colbeck, Roger; Kent, Adrian

    2013-01-04

    Device-independent quantum cryptographic schemes aim to guarantee security to users based only on the output statistics of any components used, and without the need to verify their internal functionality. Since this would protect users against untrustworthy or incompetent manufacturers, sabotage, or device degradation, this idea has excited much interest, and many device-independent schemes have been proposed. Here we identify a critical weakness of device-independent protocols that rely on public communication between secure laboratories. Untrusted devices may record their inputs and outputs and reveal information about them via publicly discussed outputs during later runs. Reusing devices thus compromises the security of a protocol and risks leaking secret data. Possible defenses include securely destroying or isolating used devices. However, these are costly and often impractical. We propose other more practical partial defenses as well as a new protocol structure for device-independent quantum key distribution that aims to achieve composable security in the case of two parties using a small number of devices to repeatedly share keys with each other (and no other party).

  16. Laser damage helps the eavesdropper in quantum cryptography.

    Science.gov (United States)

    Bugge, Audun Nystad; Sauge, Sebastien; Ghazali, Aina Mardhiyah M; Skaar, Johannes; Lydersen, Lars; Makarov, Vadim

    2014-02-21

    We propose a class of attacks on quantum key distribution (QKD) systems where an eavesdropper actively engineers new loopholes by using damaging laser illumination to permanently change properties of system components. This can turn a perfect QKD system into a completely insecure system. A proof-of-principle experiment performed on an avalanche photodiode-based detector shows that laser damage can be used to create loopholes. After ∼1  W illumination, the detectors' dark count rate reduces 2-5 times, permanently improving single-photon counting performance. After ∼1.5  W, the detectors switch permanently into the linear photodetection mode and become completely insecure for QKD applications.

  17. Upper bounds for the security of two distributed-phase reference protocols of quantum cryptography

    International Nuclear Information System (INIS)

    Branciard, Cyril; Gisin, Nicolas; Scarani, Valerio

    2008-01-01

    The differential-phase-shift (DPS) and the coherent-one-way (COW) are among the most practical protocols for quantum cryptography, and are therefore the object of fast-paced experimental developments. The assessment of their security is also a challenge for theorists: the existing tools, that allow to prove security against the most general attacks, do not apply to these two protocols in any straightforward way. We present new upper bounds for their security in the limit of large distances (d∼>50 km with typical values in optical fibers) by considering a large class of collective attacks, namely those in which the adversary attaches ancillary quantum systems to each pulse or to each pair of pulses. We introduce also two modified versions of the COW protocol, which may prove more robust than the original one

  18. A fully automated entanglement-based quantum cryptography system for telecom fiber networks

    International Nuclear Information System (INIS)

    Treiber, Alexander; Ferrini, Daniele; Huebel, Hannes; Zeilinger, Anton; Poppe, Andreas; Loruenser, Thomas; Querasser, Edwin; Matyus, Thomas; Hentschel, Michael

    2009-01-01

    We present in this paper a quantum key distribution (QKD) system based on polarization entanglement for use in telecom fibers. A QKD exchange up to 50 km was demonstrated in the laboratory with a secure key rate of 550 bits s -1 . The system is compact and portable with a fully automated start-up, and stabilization modules for polarization, synchronization and photon coupling allow hands-off operation. Stable and reliable key exchange in a deployed optical fiber of 16 km length was demonstrated. In this fiber network, we achieved over 2 weeks an automatic key generation with an average key rate of 2000 bits s -1 without manual intervention. During this period, the system had an average entanglement visibility of 93%, highlighting the technical level and stability achieved for entanglement-based quantum cryptography.

  19. Effect of imperfect Faraday mirrors on the security of a Faraday–Michelson quantum cryptography system

    International Nuclear Information System (INIS)

    Wang, Wei-Long; Gao, Ming; Ma, Zhi

    2013-01-01

    The one-way Faraday–Michelson system is a very useful practical quantum cryptography system where Faraday mirrors (FMs) play an important role. In this paper we analyze the security of this system against imperfect FMs. We consider the security loophole caused by imperfect FMs in Alice’s and Bob’s security zones. Then we implement a passive FM attack in this system. By changing the values of the imperfection parameters of Alice’s FMs, we calculate the quantum bit error rate between Alice and Bob induced by Eve and the probability that Eve obtains outcomes successfully. It is shown that the imperfection of one of Alice’s two FMs makes the system sensitive to an attack. Finally we give a modified key rate as a function of the FM imperfections. The security analysis indicates that both Alice’s and Bob’s imperfect FMs can compromise the secure key. (paper)

  20. Application of AVK and selective encryption in improving performance of quantum cryptography and networks

    International Nuclear Information System (INIS)

    Bhunia, C.T.

    2006-07-01

    The subject of quantum cryptography has emerged as an important area of research. Reported theoretical and practical investigations have conclusively established the reliable quantum key distribution (QKD) protocols with a higher level of security. For perfect security, the implementation of a time variant key is essential. The nature of cost and operation involved in quantum key distribution to distribute a time variant key from session to session/message to message has yet to be addressed from an implementation angle, yet it is understood to be hard with current available technology. Besides, the disadvantages of the subject quantum cryptanalysis, in the name of 'quantum cheating' and quantum error are demonstrated in the literature. This calls for an investigation for an affordable hybrid solution using QKD with conventional classical methods of key distribution to implement a time variant key. The paper proposes a hybrid solution towards this investigation. The solutions suggested will improve the performance of computer networks for secure transport of data in general. (author)

  1. High-dimensional quantum cryptography with twisted light

    International Nuclear Information System (INIS)

    Mirhosseini, Mohammad; Magaña-Loaiza, Omar S; O’Sullivan, Malcolm N; Rodenburg, Brandon; Malik, Mehul; Boyd, Robert W; Lavery, Martin P J; Padgett, Miles J; Gauthier, Daniel J

    2015-01-01

    Quantum key distribution (QKD) systems often rely on polarization of light for encoding, thus limiting the amount of information that can be sent per photon and placing tight bounds on the error rates that such a system can tolerate. Here we describe a proof-of-principle experiment that indicates the feasibility of high-dimensional QKD based on the transverse structure of the light field allowing for the transfer of more than 1 bit per photon. Our implementation uses the orbital angular momentum (OAM) of photons and the corresponding mutually unbiased basis of angular position (ANG). Our experiment uses a digital micro-mirror device for the rapid generation of OAM and ANG modes at 4 kHz, and a mode sorter capable of sorting single photons based on their OAM and ANG content with a separation efficiency of 93%. Through the use of a seven-dimensional alphabet encoded in the OAM and ANG bases, we achieve a channel capacity of 2.05 bits per sifted photon. Our experiment demonstrates that, in addition to having an increased information capacity, multilevel QKD systems based on spatial-mode encoding can be more resilient against intercept-resend eavesdropping attacks. (paper)

  2. Advanced active quenching circuit for ultra-fast quantum cryptography.

    Science.gov (United States)

    Stipčević, Mario; Christensen, Bradley G; Kwiat, Paul G; Gauthier, Daniel J

    2017-09-04

    Commercial photon-counting modules based on actively quenched solid-state avalanche photodiode sensors are used in a wide variety of applications. Manufacturers characterize their detectors by specifying a small set of parameters, such as detection efficiency, dead time, dark counts rate, afterpulsing probability and single-photon arrival-time resolution (jitter). However, they usually do not specify the range of conditions over which these parameters are constant or present a sufficient description of the characterization process. In this work, we perform a few novel tests on two commercial detectors and identify an additional set of imperfections that must be specified to sufficiently characterize their behavior. These include rate-dependence of the dead time and jitter, detection delay shift, and "twilighting". We find that these additional non-ideal behaviors can lead to unexpected effects or strong deterioration of the performance of a system using these devices. We explain their origin by an in-depth analysis of the active quenching process. To mitigate the effects of these imperfections, a custom-built detection system is designed using a novel active quenching circuit. Its performance is compared against two commercial detectors in a fast quantum key distribution system with hyper-entangled photons and a random number generator.

  3. Experimental fault-tolerant quantum cryptography in a decoherence-free subspace

    International Nuclear Information System (INIS)

    Zhang Qiang; Pan Jianwei; Yin Juan; Chen Tengyun; Lu Shan; Zhang Jun; Li Xiaoqiang; Yang Tao; Wang Xiangbin

    2006-01-01

    We experimentally implement a fault-tolerant quantum key distribution protocol with two photons in a decoherence-free subspace [Phys. Rev. A 72, 050304(R) (2005)]. It is demonstrated that our protocol can yield a good key rate even with a large bit-flip error rate caused by collective rotation, while the usual realization of the Bennett-Brassard 1984 protocol cannot produce any secure final key given the same channel. Since the experiment is performed in polarization space and does not need the calibration of a reference frame, important applications in free-space quantum communication are expected. Moreover, our method can also be used to robustly transmit an arbitrary two-level quantum state in a type of decoherence-free subspace

  4. Wigner representation for experiments on quantum cryptography using two-photon polarization entanglement produced in parametric down-conversion

    International Nuclear Information System (INIS)

    Casado, A; Guerra, S; Placido, J

    2008-01-01

    In this paper, the theory of parametric down-conversion in the Wigner representation is applied to Ekert's quantum cryptography protocol. We analyse the relation between two-photon entanglement and (non-secure) quantum key distribution within the Wigner framework in the Heisenberg picture. Experiments using two-qubit polarization entanglement generated in nonlinear crystals are analysed in this formalism, along with the effects of eavesdropping attacks in the case of projective measurements

  5. Wigner representation for experiments on quantum cryptography using two-photon polarization entanglement produced in parametric down-conversion

    Energy Technology Data Exchange (ETDEWEB)

    Casado, A [Departamento de Fisica Aplicada III, Escuela Superior de Ingenieros, Universidad de Sevilla, 41092 Sevilla (Spain); Guerra, S [Centro Asociado de la Universidad Nacional de Educacion a Distancia de Las Palmas de Gran Canaria (Spain); Placido, J [Departamento de Fisica, Universidad de Las Palmas de Gran Canaria (Spain)], E-mail: acasado@us.es

    2008-02-28

    In this paper, the theory of parametric down-conversion in the Wigner representation is applied to Ekert's quantum cryptography protocol. We analyse the relation between two-photon entanglement and (non-secure) quantum key distribution within the Wigner framework in the Heisenberg picture. Experiments using two-qubit polarization entanglement generated in nonlinear crystals are analysed in this formalism, along with the effects of eavesdropping attacks in the case of projective measurements.

  6. Free-space measurement-device-independent quantum-key-distribution protocol using decoy states with orbital angular momentum

    Science.gov (United States)

    Wang, Le; Zhao, Sheng-Mei; Gong, Long-Yan; Cheng, Wei-Wen

    2015-12-01

    In this paper, we propose a measurement-device-independent quantum-key-distribution (MDI-QKD) protocol using orbital angular momentum (OAM) in free space links, named the OAM-MDI-QKD protocol. In the proposed protocol, the OAM states of photons, instead of polarization states, are used as the information carriers to avoid the reference frame alignment, the decoy-state is adopted to overcome the security loophole caused by the weak coherent pulse source, and the high efficient OAM-sorter is adopted as the measurement tool for Charlie to obtain the output OAM state. Here, Charlie may be an untrusted third party. The results show that the authorized users, Alice and Bob, could distill a secret key with Charlie’s successful measurements, and the key generation performance is slightly better than that of the polarization-based MDI-QKD protocol in the two-dimensional OAM cases. Simultaneously, Alice and Bob can reduce the number of flipping the bits in the secure key distillation. It is indicated that a higher key generation rate performance could be obtained by a high dimensional OAM-MDI-QKD protocol because of the unlimited degree of freedom on OAM states. Moreover, the results show that the key generation rate and the transmission distance will decrease as the growth of the strength of atmospheric turbulence (AT) and the link attenuation. In addition, the decoy states used in the proposed protocol can get a considerable good performance without the need for an ideal source. Project supported by the National Natural Science Foundation of China (Grant Nos. 61271238 and 61475075), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20123223110003), the Natural Science Research Foundation for Universities of Jiangsu Province of China (Grant No. 11KJA510002), the Open Research Fund of Key Laboratory of Broadband Wireless Communication and Sensor Network Technology, Ministry of Education, China (Grant No. NYKL2015011), and the

  7. Quantum Information, computation and cryptography. An introductory survey of theory, technology and experiments

    International Nuclear Information System (INIS)

    Benatti, Fabio; Fannes, Mark; Floreanini, Roberto; Petritis, Dimitri

    2010-01-01

    This multi-authored textbook addresses graduate students with a background in physics, mathematics or computer science. No research experience is necessary. Consequently, rather than comprehensively reviewing the vast body of knowledge and literature gathered in the past twenty years, this book concentrates on a number of carefully selected aspects of quantum information theory and technology. Given the highly interdisciplinary nature of the subject, the multi-authored approach brings together different points of view from various renowned experts, providing a coherent picture of the subject matter. The book consists of ten chapters and includes examples, problems, and exercises. The first five present the mathematical tools required for a full comprehension of various aspects of quantum mechanics, classical information, and coding theory. Chapter 6 deals with the manipulation and transmission of information in the quantum realm. Chapters 7 and 8 discuss experimental implementations of quantum information ideas using photons and atoms. Finally, chapters 9 and 10 address ground-breaking applications in cryptography and computation. (orig.)

  8. Examination of China's performance and thematic evolution in quantum cryptography research using quantitative and computational techniques.

    Directory of Open Access Journals (Sweden)

    Nicholas V Olijnyk

    Full Text Available This study performed two phases of analysis to shed light on the performance and thematic evolution of China's quantum cryptography (QC research. First, large-scale research publication metadata derived from QC research published from 2001-2017 was used to examine the research performance of China relative to that of global peers using established quantitative and qualitative measures. Second, this study identified the thematic evolution of China's QC research using co-word cluster network analysis, a computational science mapping technique. The results from the first phase indicate that over the past 17 years, China's performance has evolved dramatically, placing it in a leading position. Among the most significant findings is the exponential rate at which all of China's performance indicators (i.e., Publication Frequency, citation score, H-index are growing. China's H-index (a normalized indicator has surpassed all other countries' over the last several years. The second phase of analysis shows how China's main research focus has shifted among several QC themes, including quantum-key-distribution, photon-optical communication, network protocols, and quantum entanglement with an emphasis on applied research. Several themes were observed across time periods (e.g., photons, quantum-key-distribution, secret-messages, quantum-optics, quantum-signatures; some themes disappeared over time (e.g., computer-networks, attack-strategies, bell-state, polarization-state, while others emerged more recently (e.g., quantum-entanglement, decoy-state, unitary-operation. Findings from the first phase of analysis provide empirical evidence that China has emerged as the global driving force in QC. Considering China is the premier driving force in global QC research, findings from the second phase of analysis provide an understanding of China's QC research themes, which can provide clarity into how QC technologies might take shape. QC and science and technology

  9. Examination of China's performance and thematic evolution in quantum cryptography research using quantitative and computational techniques.

    Science.gov (United States)

    Olijnyk, Nicholas V

    2018-01-01

    This study performed two phases of analysis to shed light on the performance and thematic evolution of China's quantum cryptography (QC) research. First, large-scale research publication metadata derived from QC research published from 2001-2017 was used to examine the research performance of China relative to that of global peers using established quantitative and qualitative measures. Second, this study identified the thematic evolution of China's QC research using co-word cluster network analysis, a computational science mapping technique. The results from the first phase indicate that over the past 17 years, China's performance has evolved dramatically, placing it in a leading position. Among the most significant findings is the exponential rate at which all of China's performance indicators (i.e., Publication Frequency, citation score, H-index) are growing. China's H-index (a normalized indicator) has surpassed all other countries' over the last several years. The second phase of analysis shows how China's main research focus has shifted among several QC themes, including quantum-key-distribution, photon-optical communication, network protocols, and quantum entanglement with an emphasis on applied research. Several themes were observed across time periods (e.g., photons, quantum-key-distribution, secret-messages, quantum-optics, quantum-signatures); some themes disappeared over time (e.g., computer-networks, attack-strategies, bell-state, polarization-state), while others emerged more recently (e.g., quantum-entanglement, decoy-state, unitary-operation). Findings from the first phase of analysis provide empirical evidence that China has emerged as the global driving force in QC. Considering China is the premier driving force in global QC research, findings from the second phase of analysis provide an understanding of China's QC research themes, which can provide clarity into how QC technologies might take shape. QC and science and technology policy researchers

  10. Generalized optical angular momentum sorter and its application to high-dimensional quantum cryptography.

    Science.gov (United States)

    Larocque, Hugo; Gagnon-Bischoff, Jérémie; Mortimer, Dominic; Zhang, Yingwen; Bouchard, Frédéric; Upham, Jeremy; Grillo, Vincenzo; Boyd, Robert W; Karimi, Ebrahim

    2017-08-21

    The orbital angular momentum (OAM) carried by optical beams is a useful quantity for encoding information. This form of encoding has been incorporated into various works ranging from telecommunications to quantum cryptography, most of which require methods that can rapidly process the OAM content of a beam. Among current state-of-the-art schemes that can readily acquire this information are so-called OAM sorters, which consist of devices that spatially separate the OAM components of a beam. Such devices have found numerous applications in optical communications, a field that is in constant demand for additional degrees of freedom, such as polarization and wavelength, into which information can also be encoded. Here, we report the implementation of a device capable of sorting a beam based on its OAM and polarization content, which could be of use in works employing both of these degrees of freedom as information channels. After characterizing our fabricated device, we demonstrate how it can be used for quantum communications via a quantum key distribution protocol.

  11. De Finetti representation theorem for infinite-dimensional quantum systems and applications to quantum cryptography.

    Science.gov (United States)

    Renner, R; Cirac, J I

    2009-03-20

    We show that the quantum de Finetti theorem holds for states on infinite-dimensional systems, provided they satisfy certain experimentally verifiable conditions. This result can be applied to prove the security of quantum key distribution based on weak coherent states or other continuous variable states against general attacks.

  12. Quantum Privacy Amplification and the Security of Quantum Cryptography over Noisy Channels

    International Nuclear Information System (INIS)

    Deutsch, D.; Ekert, A.; Jozsa, R.; Macchiavello, C.; Popescu, S.; Sanpera, A.

    1996-01-01

    Existing quantum cryptographic schemes are not, as they stand, operable in the presence of noise on the quantum communication channel. Although they become operable if they are supplemented by classical privacy-amplification techniques, the resulting schemes are difficult to analyze and have not been proved secure. We introduce the concept of quantum privacy amplification and a cryptographic scheme incorporating it which is provably secure over a noisy channel. The scheme uses an open-quote open-quote entanglement purification close-quote close-quote procedure which, because it requires only a few quantum controlled-not and single-qubit operations, could be implemented using technology that is currently being developed. copyright 1996 The American Physical Society

  13. Free-Space Quantum Key Distribution with a High Generation Rate KTP Waveguide Photon-Pair Source

    Science.gov (United States)

    Wilson, J.; Chaffee, D.; Wilson, N.; Lekki, J.; Tokars, R.; Pouch, J.; Lind, A.; Cavin, J.; Helmick, S.; Roberts, T.; hide

    2016-01-01

    NASA awarded Small Business Innovative Research (SBIR) contracts to AdvR, Inc to develop a high generation rate source of entangled photons that could be used to explore quantum key distribution (QKD) protocols. The final product, a photon pair source using a dual-element periodically- poled potassium titanyl phosphate (KTP) waveguide, was delivered to NASA Glenn Research Center in June of 2015. This paper describes the source, its characterization, and its performance in a B92 (Bennett, 1992) protocol QKD experiment.

  14. Coherent eavesdropping attacks in tomographic quantum cryptography: Nonequivalence of quantum and classical key distillation

    International Nuclear Information System (INIS)

    Kaszlikowski, Dagomir; Lim, J.Y.; Englert, Berthold-Georg; Kwek, L.C.

    2005-01-01

    The security of a cryptographic key that is generated by communication through a noisy quantum channel relies on the ability to distill a shorter secure key sequence from a longer insecure one. We show that - for protocols that use quantum channels of any dimension and completely characterize them by state tomography - the noise threshold for classical advantage distillation of a specific kind is substantially lower than the threshold for quantum entanglement distillation if the eavesdropper can perform powerful coherent attacks. In marked contrast, earlier investigations had shown that the thresholds are identical for incoherent attacks on the same classical distillation scheme. It remains an open question whether other schemes for classical advantage distillation have higher thresholds for coherent eavesdropping attacks

  15. Calculator Cryptography.

    Science.gov (United States)

    Hall, Matthew

    2003-01-01

    Uses cryptography to demonstrate the importance of algebra and the use of technology as an effective real application of mathematics. Explains simple encoding and decoding of messages for student learning of modular arithmetic. This elementary encounter with cryptography along with its historical and modern background serves to motivate student…

  16. About approximation of integer factorization problem by the combination fixed-point iteration method and Bayesian rounding for quantum cryptography

    Science.gov (United States)

    Ogorodnikov, Yuri; Khachay, Michael; Pljonkin, Anton

    2018-04-01

    We describe the possibility of employing the special case of the 3-SAT problem stemming from the well known integer factorization problem for the quantum cryptography. It is known, that for every instance of our 3-SAT setting the given 3-CNF is satisfiable by a unique truth assignment, and the goal is to find this assignment. Since the complexity status of the factorization problem is still undefined, development of approximation algorithms and heuristics adopts interest of numerous researchers. One of promising approaches to construction of approximation techniques is based on real-valued relaxation of the given 3-CNF followed by minimizing of the appropriate differentiable loss function, and subsequent rounding of the fractional minimizer obtained. Actually, algorithms developed this way differ by the rounding scheme applied on their final stage. We propose a new rounding scheme based on Bayesian learning. The article shows that the proposed method can be used to determine the security in quantum key distribution systems. In the quantum distribution the Shannon rules is applied and the factorization problem is paramount when decrypting secret keys.

  17. Free space optical communication

    CERN Document Server

    Kaushal, Hemani; Kar, Subrat

    2017-01-01

    This book provides an in-depth understanding of free space optical (FSO) communication with a particular emphasis on optical beam propagation through atmospheric turbulence. The book is structured in such a way that it provides a basic framework for the beginners and also gives a concise description from a designer’s perspective. The book provides an exposure to FSO technology, fundamental limitations, design methodologies, system trade-offs, acquisition, tracking and pointing (ATP) techniques and link-feasibility analysis. The contents of this book will be of interest to professionals and researchers alike. The book may also be used as a textbook for engineering coursework and professional training.

  18. Contemporary cryptography

    CERN Document Server

    Oppliger, Rolf

    2011-01-01

    Whether you're new to the field or looking to broaden your knowledge of contemporary cryptography, this newly revised edition of an Artech House classic puts all aspects of this important topic into perspective. Delivering an accurate introduction to the current state-of-the-art in modern cryptography, the book offers you an in-depth understanding of essential tools and applications to help you with your daily work. The second edition has been reorganized and expanded, providing mathematical fundamentals and important cryptography principles in the appropriate appendixes, rather than summarize

  19. Conventional Cryptography.

    Science.gov (United States)

    Wright, Marie A.

    1993-01-01

    Cryptography is the science that renders data unintelligible to prevent its unauthorized disclosure or modification. Presents an application of matrices used in linear transformations to illustrate a cryptographic system. An example is provided. (17 references) (MDH)

  20. Examination of China’s performance and thematic evolution in quantum cryptography research using quantitative and computational techniques

    Science.gov (United States)

    2018-01-01

    This study performed two phases of analysis to shed light on the performance and thematic evolution of China’s quantum cryptography (QC) research. First, large-scale research publication metadata derived from QC research published from 2001–2017 was used to examine the research performance of China relative to that of global peers using established quantitative and qualitative measures. Second, this study identified the thematic evolution of China’s QC research using co-word cluster network analysis, a computational science mapping technique. The results from the first phase indicate that over the past 17 years, China’s performance has evolved dramatically, placing it in a leading position. Among the most significant findings is the exponential rate at which all of China’s performance indicators (i.e., Publication Frequency, citation score, H-index) are growing. China’s H-index (a normalized indicator) has surpassed all other countries’ over the last several years. The second phase of analysis shows how China’s main research focus has shifted among several QC themes, including quantum-key-distribution, photon-optical communication, network protocols, and quantum entanglement with an emphasis on applied research. Several themes were observed across time periods (e.g., photons, quantum-key-distribution, secret-messages, quantum-optics, quantum-signatures); some themes disappeared over time (e.g., computer-networks, attack-strategies, bell-state, polarization-state), while others emerged more recently (e.g., quantum-entanglement, decoy-state, unitary-operation). Findings from the first phase of analysis provide empirical evidence that China has emerged as the global driving force in QC. Considering China is the premier driving force in global QC research, findings from the second phase of analysis provide an understanding of China’s QC research themes, which can provide clarity into how QC technologies might take shape. QC and science and technology

  1. RSA cryptography and multi prime RSA cryptography

    Science.gov (United States)

    Sani, Nur Atiqah Abdul; Kamarulhaili, Hailiza

    2017-08-01

    RSA cryptography is one of the most powerful and popular cryptosystem which is being applied until now. There is one variant of RSA cryptography named Multi Prime RSA (MPRSA) cryptography. MPRSA cryptography is the improved version of RSA cryptography. We only need to modify a few steps in key generation part and apply the Chinese Remainder Theorem (CRT) in the decryption part to get the MPRSA algorithm. The focus of this research is to compare between the standard RSA cryptography and MPRSA cryptography in a few aspects. The research shows that MPRSA cryptography is more efficient than the RSA cryptography. Time complexity using Mathematica software is also conducted and it is proven that MPRSA cryptography has shorter time taken. It also implies the computational time is less than RSA cryptography. Mathematica software version 9.0 and a laptop HP ProBook 4331s are used to check the timing and to implement both algorithms.

  2. Quantum-Secure Symmetric-Key Cryptography Based on Hidden Shifts

    DEFF Research Database (Denmark)

    Alagic, Gorjan; Russell, Alexander

    2017-01-01

    Recent results of Kaplan et al., building on work by Kuwakado and Morii, have shown that a wide variety of classically-secure symmetric-key cryptosystems can be completely broken by quantum chosen-plaintext attacks (qCPA). In such an attack, the quantum adversary has the ability to query the cryp...

  3. Randomized dynamical decoupling strategies and improved one-way key rates for quantum cryptography

    Energy Technology Data Exchange (ETDEWEB)

    Kern, Oliver

    2009-05-25

    The present thesis deals with various methods of quantum error correction. It is divided into two parts. In the first part, dynamical decoupling methods are considered which have the task of suppressing the influence of residual imperfections in a quantum memory. Such imperfections might be given by couplings between the finite dimensional quantum systems (qudits) constituting the quantum memory, for instance. The suppression is achieved by altering the dynamics of an imperfect quantum memory with the help of a sequence of local unitary operations applied to the qudits. Whereas up to now the operations of such decoupling sequences have been constructed in a deterministic fashion, strategies are developed in this thesis which construct the operations by random selection from a suitable set. Formulas are derived which estimate the average performance of such strategies. As it turns out, randomized decoupling strategies offer advantages and disadvantages over deterministic ones. It is possible to benefit from the advantages of both kind of strategies by designing combined strategies. Furthermore, it is investigated if and how the discussed decoupling strategies can be employed to protect a quantum computation running on the quantum memory. It is shown that a purely randomized decoupling strategy may be used by applying the decoupling operations and adjusted gates of the quantum algorithm in an alternating fashion. Again this method can be enhanced by the means of deterministic methods in order to obtain a combined decoupling method for quantum computations analogously to the combining strategies for quantum memories. The second part of the thesis deals with quantum error-correcting codes and protocols for quantum key distribution. The focus is on the BB84 and the 6-state protocol making use of only one-way communication during the error correction and privacy amplification steps. It is shown that by adding additional errors to the preliminary key (a process called

  4. Randomized dynamical decoupling strategies and improved one-way key rates for quantum cryptography

    International Nuclear Information System (INIS)

    Kern, Oliver

    2009-01-01

    The present thesis deals with various methods of quantum error correction. It is divided into two parts. In the first part, dynamical decoupling methods are considered which have the task of suppressing the influence of residual imperfections in a quantum memory. Such imperfections might be given by couplings between the finite dimensional quantum systems (qudits) constituting the quantum memory, for instance. The suppression is achieved by altering the dynamics of an imperfect quantum memory with the help of a sequence of local unitary operations applied to the qudits. Whereas up to now the operations of such decoupling sequences have been constructed in a deterministic fashion, strategies are developed in this thesis which construct the operations by random selection from a suitable set. Formulas are derived which estimate the average performance of such strategies. As it turns out, randomized decoupling strategies offer advantages and disadvantages over deterministic ones. It is possible to benefit from the advantages of both kind of strategies by designing combined strategies. Furthermore, it is investigated if and how the discussed decoupling strategies can be employed to protect a quantum computation running on the quantum memory. It is shown that a purely randomized decoupling strategy may be used by applying the decoupling operations and adjusted gates of the quantum algorithm in an alternating fashion. Again this method can be enhanced by the means of deterministic methods in order to obtain a combined decoupling method for quantum computations analogously to the combining strategies for quantum memories. The second part of the thesis deals with quantum error-correcting codes and protocols for quantum key distribution. The focus is on the BB84 and the 6-state protocol making use of only one-way communication during the error correction and privacy amplification steps. It is shown that by adding additional errors to the preliminary key (a process called

  5. Cryptography Basics

    DEFF Research Database (Denmark)

    Wattenhofer, Roger; Förster, Klaus-Tycho

    2017-01-01

    Public-key cryptography is one of the biggest scientific achievements of the last century. Two people that never met before can establish a common secret in plain sight? Sounds like pure magic! The idea of this chapter is to reveal some of the tricks of this “crypto magic”. This chapter is not ta......Public-key cryptography is one of the biggest scientific achievements of the last century. Two people that never met before can establish a common secret in plain sight? Sounds like pure magic! The idea of this chapter is to reveal some of the tricks of this “crypto magic”. This chapter...

  6. Quantum cryptography: individual eavesdropping with the knowledge of the error-correcting protocol

    International Nuclear Information System (INIS)

    Horoshko, D B

    2007-01-01

    The quantum key distribution protocol BB84 combined with the repetition protocol for error correction is analysed from the point of view of its security against individual eavesdropping relying on quantum memory. It is shown that the mere knowledge of the error-correcting protocol changes the optimal attack and provides the eavesdropper with additional information on the distributed key. (fifth seminar in memory of d.n. klyshko)

  7. Shor's factoring algorithm and modern cryptography. An illustration of the capabilities inherent in quantum computers

    Science.gov (United States)

    Gerjuoy, Edward

    2005-06-01

    The security of messages encoded via the widely used RSA public key encryption system rests on the enormous computational effort required to find the prime factors of a large number N using classical (conventional) computers. In 1994 Peter Shor showed that for sufficiently large N, a quantum computer could perform the factoring with much less computational effort. This paper endeavors to explain, in a fashion comprehensible to the nonexpert, the RSA encryption protocol; the various quantum computer manipulations constituting the Shor algorithm; how the Shor algorithm performs the factoring; and the precise sense in which a quantum computer employing Shor's algorithm can be said to accomplish the factoring of very large numbers with less computational effort than a classical computer. It is made apparent that factoring N generally requires many successive runs of the algorithm. Our analysis reveals that the probability of achieving a successful factorization on a single run is about twice as large as commonly quoted in the literature.

  8. A monogamy-of-entanglement game with applications to device-independent quantum cryptography

    NARCIS (Netherlands)

    M. Tomamichel; S. Fehr (Serge); J. Kaniewski; S.D.C. Wehner (Stephanie); T. Johansson; P.Q. Nguyen

    2013-01-01

    htmlabstractWe consider a game in which two separate laboratories collaborate to prepare a quantum system and are then asked to guess the outcome of a measurement performed by a third party in a random basis on that system. Intuitively, by the uncertainty principle and the monogamy of entanglement,

  9. Hybrid ququart-encoded quantum cryptography protected by Kochen-Specker contextuality

    International Nuclear Information System (INIS)

    Cabello, Adan; D'Ambrosio, Vincenzo; Nagali, Eleonora; Sciarrino, Fabio

    2011-01-01

    Quantum cryptographic protocols based on complementarity are not secure against attacks in which complementarity is imitated with classical resources. The Kochen-Specker (KS) theorem provides protection against these attacks, without requiring entanglement or spatially separated composite systems. We analyze the maximum tolerated noise to guarantee the security of a KS-protected cryptographic scheme against these attacks and describe a photonic realization of this scheme using hybrid ququarts defined by the polarization and orbital angular momentum of single photons.

  10. Improvement of two-way continuous variable quantum cryptography by using additional noise

    International Nuclear Information System (INIS)

    Wang Minjie; Pan Wei

    2010-01-01

    The performance of quantum key distribution such as one-way continuous variable protocols, can be increased by adding some noise on the reference side of error correction in the error-correction phase. For this reason, we here study this possibility in the case of two-way continuous variable system. Finally, the numerical results show that the using of additional noise gives two-way schemes better security performance in terms of secret key rates and resistance to channel excess noise.

  11. Security of continuous-variable quantum cryptography using coherent states: Decline of postselection advantage

    International Nuclear Information System (INIS)

    Namiki, Ryo; Hirano, Takuya

    2005-01-01

    We investigate the security of continuous-variable (CV) quantum key distribution (QKD) using coherent states in the presence of quadrature excess noise. We consider an eavesdropping attack that uses a linear amplifier and a beam splitter. This attack makes a link between the beam-splitting attack and the intercept-resend attack (classical teleportation attack). We also show how postselection loses its efficiency in a realistic channel

  12. A monogamy-of-entanglement game with applications to device-independent quantum cryptography

    International Nuclear Information System (INIS)

    Tomamichel, Marco; Kaniewski, Jędrzej; Wehner, Stephanie; Fehr, Serge

    2013-01-01

    We consider a game in which two separate laboratories collaborate to prepare a quantum system and are then asked to guess the outcome of a measurement performed by a third party in a random basis on that system. Intuitively, by the uncertainty principle and the monogamy of entanglement, the probability that both players simultaneously succeed in guessing the outcome correctly is bounded. We are interested in the question of how the success probability scales when many such games are performed in parallel. We show that any strategy that maximizes the probability to win every game individually is also optimal for the parallel repetition of the game. Our result implies that the optimal guessing probability can be achieved without the use of entanglement. We explore several applications of this result. Firstly, we show that it implies security for standard BB84 quantum key distribution when the receiving party uses fully untrusted measurement devices, i.e. we show that BB84 is one-sided device independent. Secondly, we show how our result can be used to prove security of a one-round position-verification scheme. Finally, we generalize a well-known uncertainty relation for the guessing probability to quantum side information. (paper)

  13. General immunity and superadditivity of two-way Gaussian quantum cryptography.

    Science.gov (United States)

    Ottaviani, Carlo; Pirandola, Stefano

    2016-03-01

    We consider two-way continuous-variable quantum key distribution, studying its security against general eavesdropping strategies. Assuming the asymptotic limit of many signals exchanged, we prove that two-way Gaussian protocols are immune to coherent attacks. More precisely we show the general superadditivity of the two-way security thresholds, which are proven to be higher than the corresponding one-way counterparts in all cases. We perform the security analysis first reducing the general eavesdropping to a two-mode coherent Gaussian attack, and then showing that the superadditivity is achieved by exploiting the random on/off switching of the two-way quantum communication. This allows the parties to choose the appropriate communication instances to prepare the key, accordingly to the tomography of the quantum channel. The random opening and closing of the circuit represents, in fact, an additional degree of freedom allowing the parties to convert, a posteriori, the two-mode correlations of the eavesdropping into noise. The eavesdropper is assumed to have no access to the on/off switching and, indeed, cannot adapt her attack. We explicitly prove that this mechanism enhances the security performance, no matter if the eavesdropper performs collective or coherent attacks.

  14. Characterization of polarization-independent phase modulation method for practical plug and play quantum cryptography

    International Nuclear Information System (INIS)

    Kwon, Osung; Lee, Min-Soo; Woo, Min Ki; Park, Byung Kwon; Kim, Il Young; Kim, Yong-Su; Han, Sang-Wook; Moon, Sung

    2015-01-01

    We characterized a polarization-independent phase modulation method, called double phase modulation, for a practical plug and play quantum key distribution (QKD) system. Following investigation of theoretical backgrounds, we applied the method to the practical QKD system and characterized the performance through comparing single phase modulation (SPM) and double phase modulation. Consequently, we obtained repeatable and accurate phase modulation confirmed by high visibility single photon interference even for input signals with arbitrary polarization. Further, the results show that only 80% of the bias voltage required in the case of single phase modulation is needed to obtain the target amount of phase modulation. (paper)

  15. A simple coherent attack and practical security of differential phase shift quantum cryptography

    International Nuclear Information System (INIS)

    Kronberg, D A

    2014-01-01

    The differential phase shift quantum key distribution protocol reveals good security against such powerful attacks as unambiguous state discrimination and beam splitting attacks. Its complete security analysis is complex due to high dimensions of the supposed spaces and density operators. In this paper, we consider a particular and conceptually simple coherent attack, available in practical implementations. The main condition for this attack is the length of used coherent state tuples of order 8–12. We show that under this condition, no high level of practical distance between legitimate users can be achieved. (paper)

  16. Single-photon counting in the 1550-nm wavelength region for quantum cryptography

    International Nuclear Information System (INIS)

    Park, Chul-Woo; Park, Jun-Bum; Park, Young-Soo; Lee, Seung-Hun; Shin, Hyun-Jun; Bae, Byung-Seong; Moon, Sung; Han, Sang-Kook

    2006-01-01

    In this paper, we report the measured performance of an InGaAs avalanche photodiode (APD) Module fabricated for single-photon counting. We measured the dark current noise, the after-pulse noise, and the quantum efficiency of the single- photon detector for different temperatures. We then examined our single-photon source and detection system by measuring the coincident probability. From our measurement, we observed that the after-pulse effect of the APD at temperatures below 105 .deg. C caused cascade noise build-up on the succeeding electrical signals.

  17. Cryptographic robustness of a quantum cryptography system using phase-time coding

    International Nuclear Information System (INIS)

    Molotkov, S. N.

    2008-01-01

    A cryptographic analysis is presented of a new quantum key distribution protocol using phase-time coding. An upper bound is obtained for the error rate that guarantees secure key distribution. It is shown that the maximum tolerable error rate for this protocol depends on the counting rate in the control time slot. When no counts are detected in the control time slot, the protocol guarantees secure key distribution if the bit error rate in the sifted key does not exceed 50%. This protocol partially discriminates between errors due to system defects (e.g., imbalance of a fiber-optic interferometer) and eavesdropping. In the absence of eavesdropping, the counts detected in the control time slot are not caused by interferometer imbalance, which reduces the requirements for interferometer stability.

  18. A contribution to quantum cryptography in finite-dimensional systems including further results from the field of quantum information theory

    International Nuclear Information System (INIS)

    Ranade, Kedar S.

    2009-01-01

    This PhD thesis deals with quantum-cryptographic protocols which allow general finite-dimensional quantum systems (qudits) as carriers of information in contrast to the predominantly used two-dimensional quantum systems (qubits). The main focus of investigations is the maximum tolerable error rate of such protocols and its behaviour as a function of the dimension of the information carriers. For this purpose, several concepts are introduced which allow the treatment of this problem. In particular, protocols are presented which work up to a maximum tolerate error rate, and it is shown that a wide class of protocols cannot be used for higher error rates. Among other things, it turns out that the maximum tolerable error rate for two-basis protocols increases up to 50% for high dimensions. Apart from the above-mentioned main subjects of this thesis, some other results from the field of quantum information theory are given, which were achieved during this PhD project. (orig.)

  19. Chocolate Key Cryptography

    Science.gov (United States)

    Bachman, Dale J.; Brown, Ezra A.; Norton, Anderson H.

    2010-01-01

    Cryptography is the science of hidden or secret writing. More generally, cryptography refers to the science of safeguarding information. Cryptography allows people to use a public medium such as the Internet to transmit private information securely, thus enabling a whole range of conveniences, from online shopping to personally printed movie…

  20. Introduction to modern cryptography

    CERN Document Server

    Katz, Jonathan

    2014-01-01

    Praise for the First Edition:""This book is a comprehensive, rigorous introduction to what the authors name 'modern' cryptography. … a novel approach to how cryptography is taught, replacing the older, construction-based approach. … The concepts are clearly stated, both in an intuitive fashion and formally. … I would heartily recommend this book to anyone who is interested in cryptography. … The exercises are challenging and interesting, and can benefit readers of all academic levels.""-IACR Book Reviews, January 2010""Over the past 30 years, cryptography has been transformed from a mysterious

  1. Electroluminescence from a single InGaN quantum dot in the green spectral region up to 150 K

    International Nuclear Information System (INIS)

    Kalden, J; Sebald, K; Gutowski, J; Tessarek, C; Figge, S; Kruse, C; Hommel, D

    2010-01-01

    We present electrically driven luminescence from single InGaN quantum dots embedded into a light emitting diode structure grown by metal-organic vapor-phase epitaxy. Single sharp emission lines in the green spectral region can be identified. Temperature dependent measurements demonstrate thermal stability of the emission of a single quantum dot up to 150 K. These results are an important step towards applications like electrically driven single-photon emitters, which are a basis for applications incorporating plastic optical fibers as well as for modern concepts of free space quantum cryptography.

  2. Quantum Security of Cryptographic Primitives

    OpenAIRE

    Gagliardoni, Tommaso

    2017-01-01

    We call quantum security the area of IT security dealing with scenarios where one or more parties have access to quantum hardware. This encompasses both the fields of post-quantum cryptography (that is, traditional cryptography engineered to be resistant against quantum adversaries), and quantum cryptography (that is, security protocols designed to be natively run on a quantum infrastructure, such as quantum key distribution). Moreover, there exist also hybrid models, where traditional crypto...

  3. Propagation of spatially entangled qudits through free space

    International Nuclear Information System (INIS)

    Lima, G.; Neves, Leonardo; Santos, Ivan F.; Padua, S.; Aguirre Gomez, J. G.; Saavedra, C.

    2006-01-01

    We show the propagation of entangled states of high-dimensional quantum systems. The qudits states were generated using the transverse correlation of the twin photons produced by spontaneous parametric down-conversion. Their free-space distribution was performed at the laboratory scale and the propagated states maintained a high fidelity with their original form. The use of entangled qudits allow an increase in the quantity of information that can be transmitted and may also guarantee more privacy for communicating parties. Therefore, studies about propagating entangled states of qudits are important for the effort of building quantum communication networks

  4. Efficiency of coherent-state quantum cryptography in the presence of loss: Influence of realistic error correction

    International Nuclear Information System (INIS)

    Heid, Matthias; Luetkenhaus, Norbert

    2006-01-01

    We investigate the performance of a continuous-variable quantum key distribution scheme in a practical setting. More specifically, we take a nonideal error reconciliation procedure into account. The quantum channel connecting the two honest parties is assumed to be lossy but noiseless. Secret key rates are given for the case that the measurement outcomes are postselected or a reverse reconciliation scheme is applied. The reverse reconciliation scheme loses its initial advantage in the practical setting. If one combines postselection with reverse reconciliation, however, much of this advantage can be recovered

  5. Entropy uncertainty relations and stability of phase-temporal quantum cryptography with finite-length transmitted strings

    Energy Technology Data Exchange (ETDEWEB)

    Molotkov, S. N., E-mail: sergei.molotkov@gmail.com [Russian Federation, Academy of Cryptography (Russian Federation)

    2012-12-15

    Any key-generation session contains a finite number of quantum-state messages, and it is there-fore important to understand the fundamental restrictions imposed on the minimal length of a string required to obtain a secret key with a specified length. The entropy uncertainty relations for smooth min and max entropies considerably simplify and shorten the proof of security. A proof of security of quantum key distribution with phase-temporal encryption is presented. This protocol provides the maximum critical error compared to other protocols up to which secure key distribution is guaranteed. In addition, unlike other basic protocols (of the BB84 type), which are vulnerable with respect to an attack by 'blinding' of avalanche photodetectors, this protocol is stable with respect to such an attack and guarantees key security.

  6. Entropy uncertainty relations and stability of phase-temporal quantum cryptography with finite-length transmitted strings

    International Nuclear Information System (INIS)

    Molotkov, S. N.

    2012-01-01

    Any key-generation session contains a finite number of quantum-state messages, and it is there-fore important to understand the fundamental restrictions imposed on the minimal length of a string required to obtain a secret key with a specified length. The entropy uncertainty relations for smooth min and max entropies considerably simplify and shorten the proof of security. A proof of security of quantum key distribution with phase-temporal encryption is presented. This protocol provides the maximum critical error compared to other protocols up to which secure key distribution is guaranteed. In addition, unlike other basic protocols (of the BB84 type), which are vulnerable with respect to an attack by “blinding” of avalanche photodetectors, this protocol is stable with respect to such an attack and guarantees key security.

  7. Analysis of Free-Space Optics Development

    Directory of Open Access Journals (Sweden)

    Mikołajczyk Janusz

    2017-12-01

    Full Text Available The article presents state of work in technology of free-space optical communications (Free Space Optics − FSO. Both commercially available optical data links and their further development are described. The main elements and operation limiting factors of FSO systems have been identified. Additionally, analyses of FSO/RF hybrid systems application are included. The main aspects of LasBITer project related to such hybrid technology for security and defence applications are presented.

  8. Quantum photonic network and physical layer security.

    Science.gov (United States)

    Sasaki, Masahide; Endo, Hiroyuki; Fujiwara, Mikio; Kitamura, Mitsuo; Ito, Toshiyuki; Shimizu, Ryosuke; Toyoshima, Morio

    2017-08-06

    Quantum communication and quantum cryptography are expected to enhance the transmission rate and the security (confidentiality of data transmission), respectively. We study a new scheme which can potentially bridge an intermediate region covered by these two schemes, which is referred to as quantum photonic network. The basic framework is information theoretically secure communications in a free space optical (FSO) wiretap channel, in which an eavesdropper has physically limited access to the main channel between the legitimate sender and receiver. We first review a theoretical framework to quantify the optimal balance of the transmission efficiency and the security level under power constraint and at finite code length. We then present experimental results on channel characterization based on 10 MHz on-off keying transmission in a 7.8 km terrestrial FSO wiretap channel.This article is part of the themed issue 'Quantum technology for the 21st century'. © 2017 The Author(s).

  9. Public Key Cryptography.

    Science.gov (United States)

    Tapson, Frank

    1996-01-01

    Describes public key cryptography, also known as RSA, which is a system using two keys, one used to put a message into cipher and another used to decipher the message. Presents examples using small prime numbers. (MKR)

  10. Neural cryptography with feedback.

    Science.gov (United States)

    Ruttor, Andreas; Kinzel, Wolfgang; Shacham, Lanir; Kanter, Ido

    2004-04-01

    Neural cryptography is based on a competition between attractive and repulsive stochastic forces. A feedback mechanism is added to neural cryptography which increases the repulsive forces. Using numerical simulations and an analytic approach, the probability of a successful attack is calculated for different model parameters. Scaling laws are derived which show that feedback improves the security of the system. In addition, a network with feedback generates a pseudorandom bit sequence which can be used to encrypt and decrypt a secret message.

  11. Halftone visual cryptography.

    Science.gov (United States)

    Zhou, Zhi; Arce, Gonzalo R; Di Crescenzo, Giovanni

    2006-08-01

    Visual cryptography encodes a secret binary image (SI) into n shares of random binary patterns. If the shares are xeroxed onto transparencies, the secret image can be visually decoded by superimposing a qualified subset of transparencies, but no secret information can be obtained from the superposition of a forbidden subset. The binary patterns of the n shares, however, have no visual meaning and hinder the objectives of visual cryptography. Extended visual cryptography [1] was proposed recently to construct meaningful binary images as shares using hypergraph colourings, but the visual quality is poor. In this paper, a novel technique named halftone visual cryptography is proposed to achieve visual cryptography via halftoning. Based on the blue-noise dithering principles, the proposed method utilizes the void and cluster algorithm [2] to encode a secret binary image into n halftone shares (images) carrying significant visual information. The simulation shows that the visual quality of the obtained halftone shares are observably better than that attained by any available visual cryptography method known to date.

  12. Quantum cryptography with finite resources: unconditional security bound for discrete-variable protocols with one-way postprocessing.

    Science.gov (United States)

    Scarani, Valerio; Renner, Renato

    2008-05-23

    We derive a bound for the security of quantum key distribution with finite resources under one-way postprocessing, based on a definition of security that is composable and has an operational meaning. While our proof relies on the assumption of collective attacks, unconditional security follows immediately for standard protocols such as Bennett-Brassard 1984 and six-states protocol. For single-qubit implementations of such protocols, we find that the secret key rate becomes positive when at least N approximately 10(5) signals are exchanged and processed. For any other discrete-variable protocol, unconditional security can be obtained using the exponential de Finetti theorem, but the additional overhead leads to very pessimistic estimates.

  13. Quantum Cryptography II: How to re-use a one-time pad safely even if P=NP.

    Science.gov (United States)

    Bennett, Charles H; Brassard, Gilles; Breidbart, Seth

    2014-01-01

    When elementary quantum systems, such as polarized photons, are used to transmit digital information, the uncertainty principle gives rise to novel cryptographic phenomena unachievable with traditional transmission media, e.g. a communications channel on which it is impossible in principle to eavesdrop without a high probability of being detected. With such a channel, a one-time pad can safely be reused many times as long as no eavesdrop is detected, and, planning ahead, part of the capacity of these uncompromised transmissions can be used to send fresh random bits with which to replace the one-time pad when an eavesdrop finally is detected. Unlike other schemes for stretching a one-time pad, this scheme does not depend on complexity-theoretic assumptions such as the difficulty of factoring.

  14. Intrinsic imperfection of self-differencing single-photon detectors harms the security of high-speed quantum cryptography systems

    Science.gov (United States)

    Jiang, Mu-Sheng; Sun, Shi-Hai; Tang, Guang-Zhao; Ma, Xiang-Chun; Li, Chun-Yan; Liang, Lin-Mei

    2013-12-01

    Thanks to the high-speed self-differencing single-photon detector (SD-SPD), the secret key rate of quantum key distribution (QKD), which can, in principle, offer unconditionally secure private communications between two users (Alice and Bob), can exceed 1 Mbit/s. However, the SD-SPD may contain loopholes, which can be exploited by an eavesdropper (Eve) to hack into the unconditional security of the high-speed QKD systems. In this paper, we analyze the fact that the SD-SPD can be remotely controlled by Eve in order to spy on full information without being discovered, then proof-of-principle experiments are demonstrated. Here, we point out that this loophole is introduced directly by the operating principle of the SD-SPD, thus, it cannot be removed, except for the fact that some active countermeasures are applied by the legitimate parties.

  15. Cryptography for Big Data Security

    Science.gov (United States)

    2015-07-13

    Cryptography for Big Data Security Book Chapter for Big Data: Storage, Sharing, and Security (3S) Distribution A: Public Release Ariel Hamlin1 Nabil...Email: arkady@ll.mit.edu ii Contents 1 Cryptography for Big Data Security 1 1.1 Introduction...48 Chapter 1 Cryptography for Big Data Security 1.1 Introduction With the amount

  16. Free Space Optical Communication for Tactical Operations

    Science.gov (United States)

    2016-09-01

    higher energy level to a lower energy level. The photons are focused to optical lenses before transmission into the air medium. The primary purpose...Security of a free space optical transmission . (n.d.). SONA Optical Wireless , [Online]. Available: http://htcbn.com/HTC_Profile_CD/fSONA/APPNOTE...almost always require on-the-move wireless communications. Radio frequency (RF) communication is used to fill the gap, but RF systems are hard pressed to

  17. Device-independence for two-party cryptography and position verification

    DEFF Research Database (Denmark)

    Ribeiro, Jeremy; Thinh, Le Phuc; Kaniewski, Jedrzej

    Quantum communication has demonstrated its usefulness for quantum cryptography far beyond quantum key distribution. One domain is two-party cryptography, whose goal is to allow two parties who may not trust each other to solve joint tasks. Another interesting application is position......-based cryptography whose goal is to use the geographical location of an entity as its only identifying credential. Unfortunately, security of these protocols is not possible against an all powerful adversary. However, if we impose some realistic physical constraints on the adversary, there exist protocols for which...... security can be proven, but these so far relied on the knowledge of the quantum operations performed during the protocols. In this work we give device-independent security proofs of two-party cryptography and Position Verification for memoryless devices under different physical constraints on the adversary...

  18. Free-space communication with over 100 spatial modes

    CSIR Research Space (South Africa)

    Rosales-Guzmán, C

    2016-10-01

    Full Text Available Congress 2016: Advanced Solid State Lasers (ASSL); Applications of Lasers for Sensing and Free Space Communications (LS&C), 30 October - 3 November 2016, Boston, Massachusetts, United States Free-space communication with over 100 spatial modes...

  19. Dynamics of neural cryptography.

    Science.gov (United States)

    Ruttor, Andreas; Kinzel, Wolfgang; Kanter, Ido

    2007-05-01

    Synchronization of neural networks has been used for public channel protocols in cryptography. In the case of tree parity machines the dynamics of both bidirectional synchronization and unidirectional learning is driven by attractive and repulsive stochastic forces. Thus it can be described well by a random walk model for the overlap between participating neural networks. For that purpose transition probabilities and scaling laws for the step sizes are derived analytically. Both these calculations as well as numerical simulations show that bidirectional interaction leads to full synchronization on average. In contrast, successful learning is only possible by means of fluctuations. Consequently, synchronization is much faster than learning, which is essential for the security of the neural key-exchange protocol. However, this qualitative difference between bidirectional and unidirectional interaction vanishes if tree parity machines with more than three hidden units are used, so that those neural networks are not suitable for neural cryptography. In addition, the effective number of keys which can be generated by the neural key-exchange protocol is calculated using the entropy of the weight distribution. As this quantity increases exponentially with the system size, brute-force attacks on neural cryptography can easily be made unfeasible.

  20. Low power cryptography

    International Nuclear Information System (INIS)

    Kitsos, P; Koufopavlou, O; Selimis, G; Sklavos, N

    2005-01-01

    Today more and more sensitive data is stored digitally. Bank accounts, medical records and personal emails are some categories that data must keep secure. The science of cryptography tries to encounter the lack of security. Data confidentiality, authentication, non-reputation and data integrity are some of the main parts of cryptography. The evolution of cryptography drove in very complex cryptographic models which they could not be implemented before some years. The use of systems with increasing complexity, which usually are more secure, has as result low throughput rate and more energy consumption. However the evolution of cipher has no practical impact, if it has only theoretical background. Every encryption algorithm should exploit as much as possible the conditions of the specific system without omitting the physical, area and timing limitations. This fact requires new ways in design architectures for secure and reliable crypto systems. A main issue in the design of crypto systems is the reduction of power consumption, especially for portable systems as smart cards. (invited paper)

  1. Dynamics of neural cryptography

    International Nuclear Information System (INIS)

    Ruttor, Andreas; Kinzel, Wolfgang; Kanter, Ido

    2007-01-01

    Synchronization of neural networks has been used for public channel protocols in cryptography. In the case of tree parity machines the dynamics of both bidirectional synchronization and unidirectional learning is driven by attractive and repulsive stochastic forces. Thus it can be described well by a random walk model for the overlap between participating neural networks. For that purpose transition probabilities and scaling laws for the step sizes are derived analytically. Both these calculations as well as numerical simulations show that bidirectional interaction leads to full synchronization on average. In contrast, successful learning is only possible by means of fluctuations. Consequently, synchronization is much faster than learning, which is essential for the security of the neural key-exchange protocol. However, this qualitative difference between bidirectional and unidirectional interaction vanishes if tree parity machines with more than three hidden units are used, so that those neural networks are not suitable for neural cryptography. In addition, the effective number of keys which can be generated by the neural key-exchange protocol is calculated using the entropy of the weight distribution. As this quantity increases exponentially with the system size, brute-force attacks on neural cryptography can easily be made unfeasible

  2. Dynamics of neural cryptography

    Science.gov (United States)

    Ruttor, Andreas; Kinzel, Wolfgang; Kanter, Ido

    2007-05-01

    Synchronization of neural networks has been used for public channel protocols in cryptography. In the case of tree parity machines the dynamics of both bidirectional synchronization and unidirectional learning is driven by attractive and repulsive stochastic forces. Thus it can be described well by a random walk model for the overlap between participating neural networks. For that purpose transition probabilities and scaling laws for the step sizes are derived analytically. Both these calculations as well as numerical simulations show that bidirectional interaction leads to full synchronization on average. In contrast, successful learning is only possible by means of fluctuations. Consequently, synchronization is much faster than learning, which is essential for the security of the neural key-exchange protocol. However, this qualitative difference between bidirectional and unidirectional interaction vanishes if tree parity machines with more than three hidden units are used, so that those neural networks are not suitable for neural cryptography. In addition, the effective number of keys which can be generated by the neural key-exchange protocol is calculated using the entropy of the weight distribution. As this quantity increases exponentially with the system size, brute-force attacks on neural cryptography can easily be made unfeasible.

  3. Distribution of high-dimensional entanglement via an intra-city free-space link.

    Science.gov (United States)

    Steinlechner, Fabian; Ecker, Sebastian; Fink, Matthias; Liu, Bo; Bavaresco, Jessica; Huber, Marcus; Scheidl, Thomas; Ursin, Rupert

    2017-07-24

    Quantum entanglement is a fundamental resource in quantum information processing and its distribution between distant parties is a key challenge in quantum communications. Increasing the dimensionality of entanglement has been shown to improve robustness and channel capacities in secure quantum communications. Here we report on the distribution of genuine high-dimensional entanglement via a 1.2-km-long free-space link across Vienna. We exploit hyperentanglement, that is, simultaneous entanglement in polarization and energy-time bases, to encode quantum information, and observe high-visibility interference for successive correlation measurements in each degree of freedom. These visibilities impose lower bounds on entanglement in each subspace individually and certify four-dimensional entanglement for the hyperentangled system. The high-fidelity transmission of high-dimensional entanglement under real-world atmospheric link conditions represents an important step towards long-distance quantum communications with more complex quantum systems and the implementation of advanced quantum experiments with satellite links.

  4. Long-distance multipartite quantum communication

    International Nuclear Information System (INIS)

    Herbst, T.

    2014-01-01

    This work addresses two long-distance free-space experiments based on multi-photon polarization entanglement. The highlighted measurements were performed between the Canary Islands La Palma and Tenerife, featuring a 143 km horizontal free-space quantum channel. Based on the superposition principle, quantum entanglement constitutes the key building block in quantum information sciences. Its nonclassical correlations lay the ground for exciting new protocols like quantum cryptography, quantum computation or quantum teleportation. Our first experiment targeted on the teleportation of entanglement, also known as entanglement swapping, where the entanglement from two polarization entangled photon pairs 0-1 and 2-3 is swapped onto photons 1-2 and 0-3. This feature constitutes the fundamental resource for so-called quantum repeaters. In the future such devices could be used to subdivide large distances into shorter links and finally extend the entanglement over the whole range by entanglement swapping. In the second experiment we realized four-photon entanglement in the form of a GHZ-state, named after the researchers Daniel Greenberger, Michael Horne and Anton Zeilinger. At the base station on La Palma we employed two sources for polarization-entanglement, generating photon pairs of 808 nm wavelength by spontaneous parametric down-conversion of femtosecond pulsed laser light. In both experiments one of the four photons per pulse was transmitted over a 143 km free-space link to the receiver station on Tenerife, whereas the remaining three photons were measured locally on La Palma. Long term atmospheric turbulences in the near-ground quantum channel were compensated by means of a bi-directional closed-loop tracking of the transceiver telescopes. Despite an average link attenuation of around 30 dB over the 143 km free-space channel, we successfully showed entanglement swapping with a statistical significance of more than 6 standard deviations. Moreover we faithfully

  5. Cryptography cracking codes

    CERN Document Server

    2014-01-01

    While cracking a code might seem like something few of us would encounter in our daily lives, it is actually far more prevalent than we may realize. Anyone who has had personal information taken because of a hacked email account can understand the need for cryptography and the importance of encryption-essentially the need to code information to keep it safe. This detailed volume examines the logic and science behind various ciphers, their real world uses, how codes can be broken, and the use of technology in this oft-overlooked field.

  6. Infrared Free Space Communication - The Autonomous Testing of Free Space Infrared Communication

    Science.gov (United States)

    Heldman, Christopher

    2017-01-01

    Fiber optics has been a winning player in the game of high-speed communication and data transfer in cable connections. Yet, in free space RF has been the repeated choice of communication medium of the space industry. Investigating the benefits of free space optical communication over radio frequency is worthwhile. An increase in science data rate return capabilities could occur if optical communication is implemented. Optical communication systems also provide efficiencies in power, mass, and volume over RF systems1. Optical communication systems have been demonstrated from a satellite in orbit with the moon to earth, and resulted in the highest data rates ever seen through space (622Mbps)2. Because of these benefits, optical communication is far superior to RF. The HiDRA (High Data Rate Architecture) project is researching Passive Misalignment Mitigation of Dynamic Free Apace Optical Communication Links. The goal of this effort is to enable gigabit per second transmission of data in short range dynamic links (less than 100 meters). In practice this would enhance data rates between sites on the International Space Station with minimal size, weight, and power requirements. This paper will focus on an autonomous code and a hardware setup that will be used to fulfill the next step in the research being conducted. The free space optical communications pointing downfalls will be investigated. This was achieved by creating 5 python programs and a top-level code to automate this test.

  7. Lightweight cryptography for constrained devices

    DEFF Research Database (Denmark)

    Alippi, Cesare; Bogdanov, Andrey; Regazzoni, Francesco

    2014-01-01

    Lightweight cryptography is a rapidly evolving research field that responds to the request for security in resource constrained devices. This need arises from crucial pervasive IT applications, such as those based on RFID tags where cost and energy constraints drastically limit the solution...... complexity, with the consequence that traditional cryptography solutions become too costly to be implemented. In this paper, we survey design strategies and techniques suitable for implementing security primitives in constrained devices....

  8. Free-space QKD system hacking by wavelength control using an external laser.

    Science.gov (United States)

    Lee, Min Soo; Woo, Min Ki; Jung, Jisung; Kim, Yong-Su; Han, Sang-Wook; Moon, Sung

    2017-05-15

    We develop a way to hack free-space quantum key distribution (QKD) systems by changing the wavelength of the quantum signal laser using an external laser. Most free-space QKD systems use four distinct lasers for each polarization, thereby making the characteristics of each laser indistinguishable. We also discover a side-channel that can distinguish the lasers by using an external laser. Our hacking scheme identifies the lasers by automatically applying the external laser to each signal laser at different intensities and detecting the wavelength variation according to the amount of incident external laser power. We conduct a proof-of-principle experiment to verify the proposed hacking structure and confirm that the wavelength varies by several gigahertzes to several nanometers, depending on the intensity of the external laser. The risk of hacking is successfully proven through the experimental results. Methods for prevention are also suggested.

  9. Cryptography Engineering Design Principles and Practical Applications

    CERN Document Server

    Ferguson, Niels; Kohno, Tadayoshi

    2012-01-01

    The ultimate guide to cryptography, updated from an author team of the world's top cryptography experts. Cryptography is vital to keeping information safe, in an era when the formula to do so becomes more and more challenging. Written by a team of world-renowned cryptography experts, this essential guide is the definitive introduction to all major areas of cryptography: message security, key negotiation, and key management. You'll learn how to think like a cryptographer. You'll discover techniques for building cryptography into products from the start and you'll examine the many technical chan

  10. Understanding and applying cryptography and data security

    CERN Document Server

    Elbirt, Adam J

    2009-01-01

    Introduction A Brief History of Cryptography and Data Security Cryptography and Data Security in the Modern World Existing Texts Book Organization Symmetric-Key Cryptography Cryptosystem Overview The Modulo Operator Greatest Common Divisor The Ring ZmHomework ProblemsSymmetric-Key Cryptography: Substitution Ciphers Basic Cryptanalysis Shift Ciphers Affine Ciphers Homework ProblemsSymmetric-Key Cryptography: Stream Ciphers Random Numbers The One-Time Pad Key Stream GeneratorsReal-World ApplicationsHomework ProblemsSymmetric-Key Cryptography: Block Ciphers The Data Encryption StandardThe Advance

  11. Introduction to cryptography

    CERN Document Server

    Buchmann, Johannes A

    2004-01-01

    Cryptography is a key technology in electronic key systems. It is used to keep data secret, digitally sign documents, access control, etc. Therefore, users should not only know how its techniques work, but they must also be able to estimate their efficiency and security. For this new edition, the author has updated the discussion of the security of encryption and signature schemes and recent advances in factoring and computing discrete logarithms. He has also added descriptions of time-memory trade of attacks and algebraic attacks on block ciphers, the Advanced Encryption Standard, the Secure Hash Algorithm, secret sharing schemes, and undeniable and blind signatures. Johannes A. Buchmann is a Professor of Computer Science and Mathematics at the Technical University of Darmstadt, and the Associate Editor of the Journal of Cryptology. In 1985, he received the Feodor Lynen Fellowship of the Alexander von Humboldt Foundation. Furthermore, he has received the most prestigious award in science in Germany, the Leib...

  12. Systems and methods for free space optical communication

    Science.gov (United States)

    Harper, Warren W [Benton City, WA; Aker, Pamela M [Richland, WA; Pratt, Richard M [Richland, WA

    2011-05-10

    Free space optical communication methods and systems, according to various aspects are described. The methods and systems are characterized by transmission of data through free space with a digitized optical signal acquired using wavelength modulation, and by discrimination between bit states in the digitized optical signal using a spectroscopic absorption feature of a chemical substance.

  13. Quantum information

    International Nuclear Information System (INIS)

    Kilin, Sergei Ya

    1999-01-01

    A new research direction known as quantum information is a multidisciplinary subject which involves quantum mechanics, optics, information theory, programming, discrete mathematics, laser physics and spectroscopy, and depends heavily on contributions from such areas as quantum computing, quantum teleportation and quantum cryptography, decoherence studies, and single-molecule and impurity spectroscopy. Some new results achieved in this rapidly growing field are discussed. (reviews of topical problems)

  14. Quantum information

    Energy Technology Data Exchange (ETDEWEB)

    Kilin, Sergei Ya [B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, Minsk (Belarus)

    1999-05-31

    A new research direction known as quantum information is a multidisciplinary subject which involves quantum mechanics, optics, information theory, programming, discrete mathematics, laser physics and spectroscopy, and depends heavily on contributions from such areas as quantum computing, quantum teleportation and quantum cryptography, decoherence studies, and single-molecule and impurity spectroscopy. Some new results achieved in this rapidly growing field are discussed. (reviews of topical problems)

  15. Coding Theory, Cryptography and Related Areas

    DEFF Research Database (Denmark)

    Buchmann, Johannes; Stichtenoth, Henning; Tapia-Recillas, Horacio

    Proceedings of anInternational Conference on Coding Theory, Cryptography and Related Areas, held in Guanajuato, Mexico. in april 1998......Proceedings of anInternational Conference on Coding Theory, Cryptography and Related Areas, held in Guanajuato, Mexico. in april 1998...

  16. Energy Pooling Upconversion in Free Space and Optical Cavities

    Science.gov (United States)

    LaCount, Michael D.

    energy pooling rate efficiency of 99%. This demonstrates that the energy pooling rate can be made faster than its competing processes. Based on the results of this study, a set of design rules was developed to optimize the rate efficiency of energy pooling. Prior to this research, no attempt had been made to determine if energy pooling could be made to out-pace competing processes--i.e. whether or not a molecular system could be designed to utilize energy pooling as an efficient means of upconversion. This initial investigation was part of a larger effort involving a team of researchers at the University of Colorado, Boulder and at the National Renewable Energy Laboratory. After establishing our computational proof-of-concept, we collectively used the new design rules to select an improved system for energy pooling. This consisted of rhodamine 6G and stilbene-420. These molecules were fabricated into a thin film, and the maximum internal quantum yield was measured to be 36% under sufficiently high intensity light. To further increase the efficiency of energy pooling, encapsulation within optical cavities was considered as a way of changing the rate of processes characterized by electric dipole-dipole coupling. This was carried out using a combination of classical electromagnetism, quantum electrodynamics, and perturbation theory. It was found that, in the near field, if the distance of the energy transfer is smaller than the distance from the energy transfer site and the cavity wall, then the electric dipole-dipole coupling tensor is not influenced by the cavity environment and the rates of energy transfer processes are the same as those in free space. Any increase in energy transfer efficiencies that are experimentally measured must therefore be caused by changing the rate of light absorption and emission. This is an important finding because earlier, less rigorous studies had concluded otherwise. It has been previously demonstrated that an optical cavity can be used to

  17. Theory and practice of chaotic cryptography

    International Nuclear Information System (INIS)

    Amigo, J.M.; Kocarev, L.; Szczepanski, J.

    2007-01-01

    In this Letter we address some basic questions about chaotic cryptography, not least the very definition of chaos in discrete systems. We propose a conceptual framework and illustrate it with different examples from private and public key cryptography. We elaborate also on possible limits of chaotic cryptography

  18. Secure quantum key distribution

    Science.gov (United States)

    Lo, Hoi-Kwong; Curty, Marcos; Tamaki, Kiyoshi

    2014-08-01

    Secure communication is crucial in the Internet Age, and quantum mechanics stands poised to revolutionize cryptography as we know it today. In this Review, we introduce the motivation and the current state of the art of research in quantum cryptography. In particular, we discuss the present security model together with its assumptions, strengths and weaknesses. After briefly introducing recent experimental progress and challenges, we survey the latest developments in quantum hacking and countermeasures against it.

  19. Coding, cryptography and combinatorics

    CERN Document Server

    Niederreiter, Harald; Xing, Chaoping

    2004-01-01

    It has long been recognized that there are fascinating connections between cod­ ing theory, cryptology, and combinatorics. Therefore it seemed desirable to us to organize a conference that brings together experts from these three areas for a fruitful exchange of ideas. We decided on a venue in the Huang Shan (Yellow Mountain) region, one of the most scenic areas of China, so as to provide the additional inducement of an attractive location. The conference was planned for June 2003 with the official title Workshop on Coding, Cryptography and Combi­ natorics (CCC 2003). Those who are familiar with events in East Asia in the first half of 2003 can guess what happened in the end, namely the conference had to be cancelled in the interest of the health of the participants. The SARS epidemic posed too serious a threat. At the time of the cancellation, the organization of the conference was at an advanced stage: all invited speakers had been selected and all abstracts of contributed talks had been screened by the p...

  20. Quantum: information theory: technological challenge

    International Nuclear Information System (INIS)

    Calixto, M.

    2001-01-01

    The new Quantum Information Theory augurs powerful machines that obey the entangled logic of the subatomic world. Parallelism, entanglement, teleportation, no-cloning and quantum cryptography are typical peculiarities of this novel way of understanding computation. (Author) 24 refs

  1. Free space optical networks for ultra-broad band services

    CERN Document Server

    Kartalopoulos, Stamatios V

    2011-01-01

    "Free Space Optical Network is a next generation communication network which uses optical waves instead of microwaves, potentially offering faster communication with ultra band width, meaning more complex communication services can be simultaneously offered. This book describes the network concepts in simple language starting with point-to-point free space optics basics and discusses networking, interoperability with existing communication network, and security. An ideal resource for communication professionals just entering the free space optical communication field and graduate students majoring in optical communications"--Provided by publisher.

  2. An introduction to mathematical cryptography

    CERN Document Server

    Hoffstein, Jeffrey; Silverman, Joseph H

    2014-01-01

    This self-contained introduction to modern cryptography emphasizes the mathematics behind the theory of public key cryptosystems and digital signature schemes. The book focuses on these key topics while developing the mathematical tools needed for the construction and security analysis of diverse cryptosystems. Only basic linear algebra is required of the reader; techniques from algebra, number theory, and probability are introduced and developed as required. This text provides an ideal introduction for mathematics and computer science students to the mathematical foundations of modern cryptography. The book includes an extensive bibliography and index; supplementary materials are available online. The book covers a variety of topics that are considered central to mathematical cryptography. Key topics include: classical cryptographic constructions, such as Diffie–Hellmann key exchange, discrete logarithm-based cryptosystems, the RSA cryptosystem, and digital signatures; fundamental mathematical tools for cr...

  3. Lightweight Cryptography for Passive RFID Tags

    DEFF Research Database (Denmark)

    David, Mathieu

    2012-01-01

    were mostly unsatisfactory. As a conclusion, a new branch of cryptography, commonly called Lightweight Cryptography, emerged to address the issues of these tiny ubiquitous devices. This Thesis presents a comprehensive engineering to lightweight cryptography, proposes a classification and explores its...... various ramifications by giving key examples in each of them. We select two of these branches, ultralightweight cryptography and symmetric-key cryptography, and propose a cryptographic primitive in each of them. In the case of symmetric-key cryptography, we propose a stream cipher that has a footprint...... of an integrator for a particular application. Finally, we conclude that the research for finding robust cryptographic primitive in the branch of lightweight cryptography still has some nice days ahead, and that providing a secure cryptosystem for printed electronics RFID tags remains an open research topic....

  4. Atmospheric free-space coherent optical communications with adaptive optics

    Science.gov (United States)

    Ting, Chueh; Zhang, Chengyu; Yang, Zikai

    2017-02-01

    Free-space coherent optical communications have a potential application to offer last mile bottleneck solution in future local area networks (LAN) because of their information carrier, information security and license-free status. Coherent optical communication systems using orthogonal frequency division multiplexing (OFDM) digital modulation are successfully demonstrated in a long-haul tens Giga bits via optical fiber, but they are not yet available in free space due to atmospheric turbulence-induced channel fading. Adaptive optics is recognized as a promising technology to mitigate the effects of atmospheric turbulence in free-space optics. In this paper, a free-space coherent optical communication system using an OFDM digital modulation scheme and adaptive optics (FSO OFDM AO) is proposed, a Gamma-Gamma distribution statistical channel fading model for the FSO OFDM AO system is examined, and FSO OFDM AO system performance is evaluated in terms of bit error rate (BER) versus various propagation distances.

  5. Cryptography from noisy storage.

    Science.gov (United States)

    Wehner, Stephanie; Schaffner, Christian; Terhal, Barbara M

    2008-06-06

    We show how to implement cryptographic primitives based on the realistic assumption that quantum storage of qubits is noisy. We thereby consider individual-storage attacks; i.e., the dishonest party attempts to store each incoming qubit separately. Our model is similar to the model of bounded-quantum storage; however, we consider an explicit noise model inspired by present-day technology. To illustrate the power of this new model, we show that a protocol for oblivious transfer is secure for any amount of quantum-storage noise, as long as honest players can perform perfect quantum operations. Our model also allows us to show the security of protocols that cope with noise in the operations of the honest players and achieve more advanced tasks such as secure identification.

  6. Exotic Optical Beam Classes for Free-Space Communication

    Science.gov (United States)

    2016-03-24

    wandering of an optical vortex is one of the significant problems with the application of vortex beams to FSO applications. From a geometrical optics ...AFRL-AFOSR-VA-TR-2016-0131 Exotic optical beam classes for free-space communication Greg Gbur UNIVERSITY OF NOTH CAROLINA AT CHARLOTTE Final Report...12-2015 4. TITLE AND SUBTITLE Exotic optical beam classes for free-space communication 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA9550-13-1-0009 5c

  7. Numerical simulation of the optimal two-mode attacks for two-way continuous-variable quantum cryptography in reverse reconciliation

    International Nuclear Information System (INIS)

    Zhang, Yichen; Zhao, Yijia; Yu, Song; Li, Zhengyu; Guo, Hong

    2017-01-01

    We analyze the security of the two-way continuous-variable quantum key distribution protocol in reverse reconciliation against general two-mode attacks, which represent all accessible attacks at fixed channel parameters. Rather than against one specific attack model, the expression of secret key rates of the two-way protocol are derived against all accessible attack models. It is found that there is an optimal two-mode attack to minimize the performance of the protocol in terms of both secret key rates and maximal transmission distances. We identify the optimal two-mode attack, give the specific attack model of the optimal two-mode attack and show the performance of the two-way protocol against the optimal two-mode attack. Even under the optimal two-mode attack, the performances of two-way protocol are still better than the corresponding one-way protocol, which shows the advantage of making double use of the quantum channel and the potential of long-distance secure communication using a two-way protocol. (paper)

  8. Cryptography as a Pedagogical Tool

    Science.gov (United States)

    Kaur, Manmohan

    2008-01-01

    In order to get undergraduates interested in mathematics, it is necessary to motivate them, give them good reasons to spend time on a subject that requires hard work, and, if possible, involve them in undergraduate research. This article discusses how cryptography can be used for all these purposes. In particular, a special topics course on…

  9. Multivariate Cryptography Based on Clipped Hopfield Neural Network.

    Science.gov (United States)

    Wang, Jia; Cheng, Lee-Ming; Su, Tong

    2018-02-01

    Designing secure and efficient multivariate public key cryptosystems [multivariate cryptography (MVC)] to strengthen the security of RSA and ECC in conventional and quantum computational environment continues to be a challenging research in recent years. In this paper, we will describe multivariate public key cryptosystems based on extended Clipped Hopfield Neural Network (CHNN) and implement it using the MVC (CHNN-MVC) framework operated in space. The Diffie-Hellman key exchange algorithm is extended into the matrix field, which illustrates the feasibility of its new applications in both classic and postquantum cryptography. The efficiency and security of our proposed new public key cryptosystem CHNN-MVC are simulated and found to be NP-hard. The proposed algorithm will strengthen multivariate public key cryptosystems and allows hardware realization practicality.

  10. Modern Quantum Technologies of Information Security

    OpenAIRE

    Korchenko, Oleksandr; Vasiliu, Yevhen; Gnatyuk, Sergiy

    2010-01-01

    In this paper, the systematisation and classification of modern quantum technologies of information security against cyber-terrorist attack are carried out. The characteristic of the basic directions of quantum cryptography from the viewpoint of the quantum technologies used is given. A qualitative analysis of the advantages and disadvantages of concrete quantum protocols is made. The current status of the problem of practical quantum cryptography use in telecommunication networks is consider...

  11. Phase-locking to a free-space terahertz comb for metrological-grade terahertz lasers.

    Science.gov (United States)

    Consolino, L; Taschin, A; Bartolini, P; Bartalini, S; Cancio, P; Tredicucci, A; Beere, H E; Ritchie, D A; Torre, R; Vitiello, M S; De Natale, P

    2012-01-01

    Optical frequency comb synthesizers have represented a revolutionary approach to frequency metrology, providing a grid of frequency references for any laser emitting within their spectral coverage. Extending the metrological features of optical frequency comb synthesizers to the terahertz domain would be a major breakthrough, due to the widespread range of accessible strategic applications and the availability of stable, high-power and widely tunable sources such as quantum cascade lasers. Here we demonstrate phase-locking of a 2.5 THz quantum cascade laser to a free-space comb, generated in a LiNbO(3) waveguide and covering the 0.1-6 THz frequency range. We show that even a small fraction (quantum cascade laser is sufficient to generate a beat note suitable for phase-locking to the comb, paving the way to novel metrological-grade terahertz applications, including high-resolution spectroscopy, manipulation of cold molecules, astronomy and telecommunications.

  12. Security by quantum key distribution and IPSEC (SEQKEIP): feasibility

    International Nuclear Information System (INIS)

    Sfaxi, M.A.; Ghernaouti-Helie, S.; Ribordy, G; Gay, O.

    2005-01-01

    Full text: Classical cryptography algorithms are based on mathematical functions. The robustness of a given cryptosystem is based essentially on the secrecy of its (private) key and the difficulty with which the inverse of its one-way function(s) can be calculated. Unfortunately, there is no mathematical proof that will establish whether it is not possible to find the inverse of a given one-way function. On the contrary, quantum cryptography is a method for sharing secret keys, whose security can be formally demonstrated. It is based on the laws of physics. The possible applications of quantum cryptography are mainly linked to telecommunication services that require very high level of security. Quantum cryptography could be integrated in various existing concepts and protocols. One of the possible use of quantum cryptography is within IPSEC. The aim of this paper is to analyse the feasibility of using quantum cryptography in IPSEC and to present the estimated performances of this solution. (author)

  13. Quantum secure communication models comparison

    Directory of Open Access Journals (Sweden)

    Georgi Petrov Bebrov

    2017-12-01

    Full Text Available The paper concerns the quantum cryptography, more specifically, the quantum secure communication type of schemes. The main focus here is on making a comparison between the distinct secure quantum communication models – quantum secure direct communication and deterministic secure quantum communication, in terms of three parameters: resource efficiency, eavesdropping check efficiency, and security (degree of preserving the confidentiality.

  14. Research progress of free space coherent optical communication

    Science.gov (United States)

    Tan, Zhenkun; Ke, Xizheng

    2018-02-01

    This paper mainly introduces the research progress of free space coherent optical communication in Xi'an University of Technology. In recent years, the research on the outer modulation technology of the laser, free-space-to-fiber coupling technique, the design of transmitting and receiving optical antenna, adaptive optical technology with or without wave-front sensor, automatic polarization control technology, frequency stabilization technology, heterodyne detection technology and high speed signal processing technology. Based on the above related research, the digital signal modulation, transmission, detection and data recovery are realized by the heterodyne detection technology in the free space optical communication system, and finally the function of smooth viewing high-definition video is realized.

  15. Everyday cryptography fundamental principles and applications

    CERN Document Server

    Martin, Keith M

    2012-01-01

    Cryptography is a vital technology that underpins the security of information in computer networks. This book presents a comprehensive introduction to the role that cryptography plays in providing information security for technologies such as the Internet, mobile phones, payment cards, and wireless local area networks. Focusing on the fundamental principles that ground modern cryptography as they arise in modern applications, it avoids both an over-reliance on transient currenttechnologies and over-whelming theoretical research.Everyday Cryptography is a self-contained and widely accessible in

  16. NASA's current activities in free space optical communications

    Science.gov (United States)

    Edwards, Bernard L.

    2017-11-01

    NASA and other space agencies around the world are currently developing free space optical communication systems for both space-to-ground links and space-to-space links. This paper provides an overview of NASA's current activities in free space optical communications with a focus on Near Earth applications. Activities to be discussed include the Lunar Laser Communication Demonstration, the Laser Communications Relay Demonstration, and the commercialization of the underlying technology. The paper will also briefly discuss ongoing efforts and studies for Deep Space optical communications. Finally the paper will discuss the development of international optical communication standards within the Consultative Committee for Space Data Systems.

  17. Optical hiding with visual cryptography

    Science.gov (United States)

    Shi, Yishi; Yang, Xiubo

    2017-11-01

    We propose an optical hiding method based on visual cryptography. In the hiding process, we convert the secret information into a set of fabricated phase-keys, which are completely independent of each other, intensity-detected-proof and image-covered, leading to the high security. During the extraction process, the covered phase-keys are illuminated with laser beams and then incoherently superimposed to extract the hidden information directly by human vision, without complicated optical implementations and any additional computation, resulting in the convenience of extraction. Also, the phase-keys are manufactured as the diffractive optical elements that are robust to the attacks, such as the blocking and the phase-noise. Optical experiments verify that the high security, the easy extraction and the strong robustness are all obtainable in the visual-cryptography-based optical hiding.

  18. Device independence for two-party cryptography and position verification with memoryless devices

    Science.gov (United States)

    Ribeiro, Jérémy; Thinh, Le Phuc; Kaniewski, Jedrzej; Helsen, Jonas; Wehner, Stephanie

    2018-06-01

    Quantum communication has demonstrated its usefulness for quantum cryptography far beyond quantum key distribution. One domain is two-party cryptography, whose goal is to allow two parties who may not trust each other to solve joint tasks. Another interesting application is position-based cryptography whose goal is to use the geographical location of an entity as its only identifying credential. Unfortunately, security of these protocols is not possible against an all powerful adversary. However, if we impose some realistic physical constraints on the adversary, there exist protocols for which security can be proven, but these so far relied on the knowledge of the quantum operations performed during the protocols. In this work we improve the device-independent security proofs of Kaniewski and Wehner [New J. Phys. 18, 055004 (2016), 10.1088/1367-2630/18/5/055004] for two-party cryptography (with memoryless devices) and we add a security proof for device-independent position verification (also memoryless devices) under different physical constraints on the adversary. We assess the quality of the devices by observing a Bell violation, and, as for Kaniewski and Wehner [New J. Phys. 18, 055004 (2016), 10.1088/1367-2630/18/5/055004], security can be attained for any violation of the Clauser-Holt-Shimony-Horne inequality.

  19. Free Space Optics Communication for Mobile Military Platforms

    Science.gov (United States)

    2003-12-01

    Federal Communications Commission FDA Food and Drug Administration FOV Field-of-View FSO Free Space Optics FWHM Full Width at Half Maximum Gbps...Physique et de Métrologie des Oscillateurs (LPMO) du CNRS UPR3203, associé à l’Université de Franche -Comté, 15 March 2002 [Schenk 2000] H. Schenk

  20. One-carrier free space charge motion under applied voltage

    International Nuclear Information System (INIS)

    Camargo, P.C.; Ferreira, G.F.L.

    1976-01-01

    The system of partial differential equations describing the one-carrier free space-charge motion under a given applied voltage is transformed into a system of two ordinary differential equations. The method is applied to find the external current injection [pt

  1. Quantum optics

    Energy Technology Data Exchange (ETDEWEB)

    Drummond, P D [University of Queensland, St. Lucia, QLD (Australia).Physics Department

    1999-07-01

    Full text: Quantum optics in Australia has been an active research field for some years. I shall focus on recent developments in quantum and atom optics. Generally, the field as a whole is becoming more and more diverse, as technological developments drive experiments into new areas, and theorists either attempt to explain the new features, or else develop models for even more exotic ideas. The recent developments include quantum solitons, quantum computing, Bose-Einstein condensation, atom lasers, quantum cryptography, and novel tests of quantum mechanics. The talk will briefly cover current progress and outstanding problems in each of these areas. Copyright (1999) Australian Optical Society.

  2. Three-dimensional theory for interaction between atomic ensembles and free-space light

    International Nuclear Information System (INIS)

    Duan, L.-M.; Cirac, J.I.; Zoller, P.

    2002-01-01

    Atomic ensembles have shown to be a promising candidate for implementations of quantum information processing by many recently discovered schemes. All these schemes are based on the interaction between optical beams and atomic ensembles. For description of these interactions, one assumed either a cavity-QED model or a one-dimensional light propagation model, which is still inadequate for a full prediction and understanding of most of the current experimental efforts that are actually taken in the three-dimensional free space. Here, we propose a perturbative theory to describe the three-dimensional effects in interaction between atomic ensembles and free-space light with a level configuration important for several applications. The calculations reveal some significant effects that were not known before from the other approaches, such as the inherent mode-mismatching noise and the optimal mode-matching conditions. The three-dimensional theory confirms the collective enhancement of the signal-to-noise ratio which is believed to be one of the main advantages of the ensemble-based quantum information processing schemes, however, it also shows that this enhancement needs to be understood in a more subtle way with an appropriate mode-matching method

  3. Quantum key distribution via quantum encryption

    CERN Document Server

    Yong Sheng Zhang; Guang Can Guo

    2001-01-01

    A quantum key distribution protocol based on quantum encryption is presented in this Brief Report. In this protocol, the previously shared Einstein-Podolsky-Rosen pairs act as the quantum key to encode and decode the classical cryptography key. The quantum key is reusable and the eavesdropper cannot elicit any information from the particle Alice sends to Bob. The concept of quantum encryption is also discussed. (21 refs).

  4. Report of the Public Cryptography Study Group.

    Science.gov (United States)

    American Council on Education, Washington, DC.

    Concerns of the National Security Agency (NSA) that information contained in some articles about cryptography in learned and professional journals and in monographs might be inimical to the national security are addressed. The Public Cryptography Study Group, with one dissenting opinion, recommends that a voluntary system of prior review of…

  5. Security, Privacy, and Applied Cryptography Engineering

    DEFF Research Database (Denmark)

    This book constitutes the refereed proceedings of the Second International Conference on Security, Privacy and Applied Cryptography Engineering held in Chennai, India, in November 2012. The 11 papers presented were carefully reviewed and selected from 61 submissions. The papers are organized...... and applications, high-performance computing in cryptology and cryptography in ubiquitous devices....

  6. Eavesdropping without quantum memory

    International Nuclear Information System (INIS)

    Bechmann-Pasquinucci, H.

    2006-01-01

    In quantum cryptography the optimal eavesdropping strategy requires that the eavesdropper uses ancillas and quantum memories in order to optimize her information. What happens if the eavesdropper has no quantum memory? It is shown that in this case the eavesdropper obtains a better information/disturbance trade-off by adopting the simple intercept/resend strategy

  7. Device-independent two-party cryptography secure against sequential attacks

    DEFF Research Database (Denmark)

    Kaniewski, Jedrzej; Wehner, Stephanie

    2016-01-01

    The goal of two-party cryptography is to enable two parties, Alice and Bob, to solve common tasks without the need for mutual trust. Examples of such tasks are private access to a database, and secure identification. Quantum communication enables security for all of these problems in the noisy......-storage model by sending more signals than the adversary can store in a certain time frame. Here, we initiate the study of device-independent (DI) protocols for two-party cryptography in the noisy-storage model. Specifically, we present a relatively easy to implement protocol for a cryptographic building block...... known as weak string erasure and prove its security even if the devices used in the protocol are prepared by the dishonest party. DI two-party cryptography is made challenging by the fact that Alice and Bob do not trust each other, which requires new techniques to establish security. We fully analyse...

  8. Special Issue on Entropy-Based Applied Cryptography and Enhanced Security for Ubiquitous Computing

    Directory of Open Access Journals (Sweden)

    James (Jong Hyuk Park

    2016-09-01

    Full Text Available Entropy is a basic and important concept in information theory. It is also often used as a measure of the unpredictability of a cryptographic key in cryptography research areas. Ubiquitous computing (Ubi-comp has emerged rapidly as an exciting new paradigm. In this special issue, we mainly selected and discussed papers related with ore theories based on the graph theory to solve computational problems on cryptography and security, practical technologies; applications and services for Ubi-comp including secure encryption techniques, identity and authentication; credential cloning attacks and countermeasures; switching generator with resistance against the algebraic and side channel attacks; entropy-based network anomaly detection; applied cryptography using chaos function, information hiding and watermark, secret sharing, message authentication, detection and modeling of cyber attacks with Petri Nets, and quantum flows for secret key distribution, etc.

  9. A contribution to quantum cryptography in finite-dimensional systems including further results from the field of quantum information theory; Ein Beitrag zur Quantenkryptographie in endlichdimensionalen Systemen nebst weiteren Ergebnissen aus dem Gebiet der Quanteninformationstheorie

    Energy Technology Data Exchange (ETDEWEB)

    Ranade, Kedar S.

    2009-02-04

    This PhD thesis deals with quantum-cryptographic protocols which allow general finite-dimensional quantum systems (qudits) as carriers of information in contrast to the predominantly used two-dimensional quantum systems (qubits). The main focus of investigations is the maximum tolerable error rate of such protocols and its behaviour as a function of the dimension of the information carriers. For this purpose, several concepts are introduced which allow the treatment of this problem. In particular, protocols are presented which work up to a maximum tolerate error rate, and it is shown that a wide class of protocols cannot be used for higher error rates. Among other things, it turns out that the maximum tolerable error rate for two-basis protocols increases up to 50% for high dimensions. Apart from the above-mentioned main subjects of this thesis, some other results from the field of quantum information theory are given, which were achieved during this PhD project. (orig.)

  10. Quantum computing with trapped ions

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, R.J.

    1998-01-01

    The significance of quantum computation for cryptography is discussed. Following a brief survey of the requirements for quantum computational hardware, an overview of the ion trap quantum computation project at Los Alamos is presented. The physical limitations to quantum computation with trapped ions are analyzed and an assessment of the computational potential of the technology is made.

  11. Cryptography in constant parallel time

    CERN Document Server

    Applebaum, Benny

    2013-01-01

    Locally computable (NC0) functions are 'simple' functions for which every bit of the output can be computed by reading a small number of bits of their input. The study of locally computable cryptography attempts to construct cryptographic functions that achieve this strong notion of simplicity and simultaneously provide a high level of security. Such constructions are highly parallelizable and they can be realized by Boolean circuits of constant depth.This book establishes, for the first time, the possibility of local implementations for many basic cryptographic primitives such as one-way func

  12. Cooperating attackers in neural cryptography.

    Science.gov (United States)

    Shacham, Lanir N; Klein, Einat; Mislovaty, Rachel; Kanter, Ido; Kinzel, Wolfgang

    2004-06-01

    A successful attack strategy in neural cryptography is presented. The neural cryptosystem, based on synchronization of neural networks by mutual learning, has been recently shown to be secure under different attack strategies. The success of the advanced attacker presented here, called the "majority-flipping attacker," does not decay with the parameters of the model. This attacker's outstanding success is due to its using a group of attackers which cooperate throughout the synchronization process, unlike any other attack strategy known. An analytical description of this attack is also presented, and fits the results of simulations.

  13. Quantum key management

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, Richard John; Thrasher, James Thomas; Nordholt, Jane Elizabeth

    2016-11-29

    Innovations for quantum key management harness quantum communications to form a cryptography system within a public key infrastructure framework. In example implementations, the quantum key management innovations combine quantum key distribution and a quantum identification protocol with a Merkle signature scheme (using Winternitz one-time digital signatures or other one-time digital signatures, and Merkle hash trees) to constitute a cryptography system. More generally, the quantum key management innovations combine quantum key distribution and a quantum identification protocol with a hash-based signature scheme. This provides a secure way to identify, authenticate, verify, and exchange secret cryptographic keys. Features of the quantum key management innovations further include secure enrollment of users with a registration authority, as well as credential checking and revocation with a certificate authority, where the registration authority and/or certificate authority can be part of the same system as a trusted authority for quantum key distribution.

  14. Cryptography and computational number theory

    CERN Document Server

    Shparlinski, Igor; Wang, Huaxiong; Xing, Chaoping; Workshop on Cryptography and Computational Number Theory, CCNT'99

    2001-01-01

    This volume contains the refereed proceedings of the Workshop on Cryptography and Computational Number Theory, CCNT'99, which has been held in Singapore during the week of November 22-26, 1999. The workshop was organized by the Centre for Systems Security of the Na­ tional University of Singapore. We gratefully acknowledge the financial support from the Singapore National Science and Technology Board under the grant num­ ber RP960668/M. The idea for this workshop grew out of the recognition of the recent, rapid development in various areas of cryptography and computational number the­ ory. The event followed the concept of the research programs at such well-known research institutions as the Newton Institute (UK), Oberwolfach and Dagstuhl (Germany), and Luminy (France). Accordingly, there were only invited lectures at the workshop with plenty of time for informal discussions. It was hoped and successfully achieved that the meeting would encourage and stimulate further research in information and computer s...

  15. Interference of Single Photons Emitted by Entangled Atoms in Free Space

    Science.gov (United States)

    Araneda, G.; Higginbottom, D. B.; Slodička, L.; Colombe, Y.; Blatt, R.

    2018-05-01

    The generation and manipulation of entanglement between isolated particles has precipitated rapid progress in quantum information processing. Entanglement is also known to play an essential role in the optical properties of atomic ensembles, but fundamental effects in the controlled emission and absorption from small, well-defined numbers of entangled emitters in free space have remained unobserved. Here we present the control of the emission rate of a single photon from a pair of distant, entangled atoms into a free-space optical mode. Changing the length of the optical path connecting the atoms modulates the single-photon emission rate in the selected mode with a visibility V =0.27 ±0.03 determined by the degree of entanglement shared between the atoms, corresponding directly to the concurrence Cρ=0.31 ±0.10 of the prepared state. This scheme, together with population measurements, provides a fully optical determination of the amount of entanglement. Furthermore, large sensitivity of the interference phase evolution points to applications of the presented scheme in high-precision gradient sensing.

  16. Quantum: information theory: technological challenge; Computacion Cuantica: un reto tecnologico

    Energy Technology Data Exchange (ETDEWEB)

    Calixto, M.

    2001-07-01

    The new Quantum Information Theory augurs powerful machines that obey the entangled logic of the subatomic world. Parallelism, entanglement, teleportation, no-cloning and quantum cryptography are typical peculiarities of this novel way of understanding computation. (Author) 24 refs.

  17. Bent functions results and applications to cryptography

    CERN Document Server

    Tokareva, Natalia

    2015-01-01

    Bent Functions: Results and Applications to Cryptography offers a unique survey of the objects of discrete mathematics known as Boolean bent functions. As these maximal, nonlinear Boolean functions and their generalizations have many theoretical and practical applications in combinatorics, coding theory, and cryptography, the text provides a detailed survey of their main results, presenting a systematic overview of their generalizations and applications, and considering open problems in classification and systematization of bent functions. The text is appropriate for novices and advanced

  18. Mathematical Background of Public Key Cryptography

    DEFF Research Database (Denmark)

    Frey, Gerhard; Lange, Tanja

    2005-01-01

    The two main systems used for public key cryptography are RSA and protocols based on the discrete logarithm problem in some cyclic group. We focus on the latter problem and state cryptographic protocols and mathematical background material.......The two main systems used for public key cryptography are RSA and protocols based on the discrete logarithm problem in some cyclic group. We focus on the latter problem and state cryptographic protocols and mathematical background material....

  19. Cryptography with chaos using Chua's system

    International Nuclear Information System (INIS)

    Oliveira, C H; Pizolato, J C Jr

    2011-01-01

    In the last years, chaotic systems have been applied in information security. These systems have a complex and unpredictable behavior, what makes them more attractive for data cryptography applications. In this work, the chaotic behavior of signals generated by Chua's system is combined with the original information in order to obtain a safe cryptographic method. The experimental results demonstrate that the proposed scheme can be used in data cryptography applications.

  20. APPLICATION OF NATURAL TRANSFORM IN CRYPTOGRAPHY

    OpenAIRE

    Chindhe, Anil Dhondiram; Kiwne, Sakharam

    2017-01-01

    Abstaract−The newly defined integral transform ”Natural transform” has many application in the field of science and engineering.In this paper we described the application of Natural transform to Cryptography.This provide the algorithm for cryptography in which we use the natural transform of the exponential function for encryption of the plain text and corresponding inverse natural transform for decryption

  1. Free-space wavelength-multiplexed optical scanner.

    Science.gov (United States)

    Yaqoob, Z; Rizvi, A A; Riza, N A

    2001-12-10

    A wavelength-multiplexed optical scanning scheme is proposed for deflecting a free-space optical beam by selection of the wavelength of the light incident on a wavelength-dispersive optical element. With fast tunable lasers or optical filters, this scanner features microsecond domain scan setting speeds and large- diameter apertures of several centimeters or more for subdegree angular scans. Analysis performed indicates an optimum scan range for a given diffraction order and grating period. Limitations include beam-spreading effects based on the varying scanner aperture sizes and the instantaneous information bandwidth of the data-carrying laser beam.

  2. Reliability issues of free-space communications systems and networks

    Science.gov (United States)

    Willebrand, Heinz A.

    2003-04-01

    Free space optics (FSO) is a high-speed point-to-point connectivity solution traditionally used in the enterprise campus networking market for building-to-building LAN connectivity. However, more recently some wire line and wireless carriers started to deploy FSO systems in their networks. The requirements on FSO system reliability, meaing both system availability and component reliability, are far more stringent in the carrier market when compared to the requirements in the enterprise market segment. This paper tries to outline some of the aspects that are important to ensure carrier class system reliability.

  3. Spontaneous emergence of free-space optical and atomic patterns

    International Nuclear Information System (INIS)

    Schmittberger, Bonnie L; Gauthier, Daniel J

    2016-01-01

    The spontaneous formation of patterns in dynamical systems is a rich phenomenon that transcends scientific boundaries. Here, we report our observation of coupled optical–atomic pattern formation, which results in the creation of self-organized, multimode structures in free-space laser-driven cold atoms. We show that this process gives rise to spontaneous three-dimensional Sisyphus cooling even at very low light intensities and the emergence of self-organized structures on both sub- and super-wavelength scales. (paper)

  4. Beam-width spreading of vortex beams in free space

    Science.gov (United States)

    Wang, Weiwei; Li, Jinhong; Duan, Meiling

    2018-01-01

    Based on the extended Huygens-Fresnel principle and the definition of second-order moments of the Wigner distribution function, the analytical expression for the beam-width spreading of Gaussian Schell-model (GSM) vortex beams in free space are derived, and used to study the influence of beam parameters on the beam-width spreading of GSM vortex beams. With the increment of the propagation distance, the beam-width spreading of GSM vortex beams will increase; the bigger the topological charge, spatial correlation length, wavelength and waist width are, the smaller the beam-width spreading is.

  5. Video semaphore decoding for free-space optical communication

    Science.gov (United States)

    Last, Matthew; Fisher, Brian; Ezekwe, Chinwuba; Hubert, Sean M.; Patel, Sheetal; Hollar, Seth; Leibowitz, Brian S.; Pister, Kristofer S. J.

    2001-04-01

    Using teal-time image processing we have demonstrated a low bit-rate free-space optical communication system at a range of more than 20km with an average optical transmission power of less than 2mW. The transmitter is an autonomous one cubic inch microprocessor-controlled sensor node with a laser diode output. The receiver is a standard CCD camera with a 1-inch aperture lens, and both hardware and software implementations of the video semaphore decoding algorithm. With this system sensor data can be reliably transmitted 21 km form San Francisco to Berkeley.

  6. An Introduction to Free-space Optical Communications

    Directory of Open Access Journals (Sweden)

    H. Henniger

    2010-06-01

    Full Text Available Over the last two decades free-space optical communication (FSO has become more and more interesting as an adjunct or alternative to radio frequency communication. This article gives an overview of the challenges a system designer has to consider while implementing an FSO system. Typical gains and losses along the path from the transmitter through the medium to the receiver are introduced in this article. Detailed discussions of these topics can be found in this special issue of the Radioengineering Journal.

  7. Babinet-Inverted Optical Yagi-Uda Antenna for Unidirectional Radiation to Free Space

    Science.gov (United States)

    Kim, Jineun; Roh, Young-Geun; Cheon, Sangmo; Choe, Jong-Ho; Lee, Jongcheon; Lee, Jaesoong; Jeong, Heejeong; Kim, Un Jeong; Park, Yeonsang; Song, In Yong; Park, Q.-Han; Hwang, Sung Woo; Kim, Kinam; Lee, Chang-Won

    2014-06-01

    Plasmonic nanoantennas are key elements in nanophotonics capable of directing radiation or enhancing the transition rate of a quantum emitter. Slot-type magnetic-dipole nanoantennas, which are complementary structures of typical electric-dipole-type antennas, have received little attention, leaving their antenna properties largely unexplored. Here we present a novel magnetic-dipole-fed multi-slot optical Yagi-Uda antenna. By engineering the relative phase of the interacting surface plasmon polaritons between the slot elements, we demonstrate that the optical antenna exhibits highly unidirectional radiation to free space. The unique features of the slot-based magnetic nanoantenna provide a new possibility of achieving integrated features such as energy transfer from one waveguide to another by working as a future optical via.

  8. Cryptography with chaos and shadowing

    International Nuclear Information System (INIS)

    Smaoui, Nejib; Kanso, Ali

    2009-01-01

    In this paper, we present a novel approach to encrypt a message (a text composed by some alphabets) using chaos and shadowing. First, we generate a numerical chaotic orbit based on the logistic map, and use the shadowing algorithm of Smaoui and Kostelich [Smaoui N, Kostelich E. Using chaos to shadow the quadratic map for all time. Int J Comput Math 1998;70:117-29] to show that there exists a finite number of true orbits that shadow the numerical orbit. Then, the finite number of maps generated is used in Baptista's algorithm [Baptista MS. Cryptography with chaos. Phys Lett A 1998;240:50-4] to encrypt each character of the message. It is shown that the use of chaos and shadowing in the encryption process enhances the security level.

  9. Cryptographie quantique à variables continues

    Science.gov (United States)

    Bencheikh, K.; Jankovic, A.; Symul, T.; Levenson, J. A.

    2002-06-01

    Nous avons élaboré un protocole de cryptographie quantique qui permet de générer et de distribuer une clé secrète aléatoire. Le protocole repose sur l'utilisation de paires de champs électromagnétiques dont les quadratures présentent des corrélations quantiques de type Einstein-Podolsky-Rosen. Les fluctuations quantiques instantanése constituent les bits aléatoires de la clé secrète, et la dégradation irréversible des corrélations quantiques des quadratures causée par une tierce personne permet de la détecter et de garantir la sécurité d'échange.

  10. Iris Cryptography for Security Purpose

    Science.gov (United States)

    Ajith, Srighakollapu; Balaji Ganesh Kumar, M.; Latha, S.; Samiappan, Dhanalakshmi; Muthu, P.

    2018-04-01

    In today's world, the security became the major issue to every human being. A major issue is hacking as hackers are everywhere, as the technology was developed still there are many issues where the technology fails to meet the security. Engineers, scientists were discovering the new products for security purpose as biometrics sensors like face recognition, pattern recognition, gesture recognition, voice authentication etcetera. But these devices fail to reach the expected results. In this work, we are going to present an approach to generate a unique secure key using the iris template. Here the iris templates are processed using the well-defined processing techniques. Using the encryption and decryption process they are stored, traversed and utilized. As of the work, we can conclude that the iris cryptography gives us the expected results for securing the data from eavesdroppers.

  11. Genetic attack on neural cryptography.

    Science.gov (United States)

    Ruttor, Andreas; Kinzel, Wolfgang; Naeh, Rivka; Kanter, Ido

    2006-03-01

    Different scaling properties for the complexity of bidirectional synchronization and unidirectional learning are essential for the security of neural cryptography. Incrementing the synaptic depth of the networks increases the synchronization time only polynomially, but the success of the geometric attack is reduced exponentially and it clearly fails in the limit of infinite synaptic depth. This method is improved by adding a genetic algorithm, which selects the fittest neural networks. The probability of a successful genetic attack is calculated for different model parameters using numerical simulations. The results show that scaling laws observed in the case of other attacks hold for the improved algorithm, too. The number of networks needed for an effective attack grows exponentially with increasing synaptic depth. In addition, finite-size effects caused by Hebbian and anti-Hebbian learning are analyzed. These learning rules converge to the random walk rule if the synaptic depth is small compared to the square root of the system size.

  12. Cheating prevention in visual cryptography.

    Science.gov (United States)

    Hu, Chih-Ming; Tzeng, Wen-Guey

    2007-01-01

    Visual cryptography (VC) is a method of encrypting a secret image into shares such that stacking a sufficient number of shares reveals the secret image. Shares are usually presented in transparencies. Each participant holds a transparency. Most of the previous research work on VC focuses on improving two parameters: pixel expansion and contrast. In this paper, we studied the cheating problem in VC and extended VC. We considered the attacks of malicious adversaries who may deviate from the scheme in any way. We presented three cheating methods and applied them on attacking existent VC or extended VC schemes. We improved one cheat-preventing scheme. We proposed a generic method that converts a VCS to another VCS that has the property of cheating prevention. The overhead of the conversion is near optimal in both contrast degression and pixel expansion.

  13. Combining Cryptography with EEG Biometrics.

    Science.gov (United States)

    Damaševičius, Robertas; Maskeliūnas, Rytis; Kazanavičius, Egidijus; Woźniak, Marcin

    2018-01-01

    Cryptographic frameworks depend on key sharing for ensuring security of data. While the keys in cryptographic frameworks must be correctly reproducible and not unequivocally connected to the identity of a user, in biometric frameworks this is different. Joining cryptography techniques with biometrics can solve these issues. We present a biometric authentication method based on the discrete logarithm problem and Bose-Chaudhuri-Hocquenghem (BCH) codes, perform its security analysis, and demonstrate its security characteristics. We evaluate a biometric cryptosystem using our own dataset of electroencephalography (EEG) data collected from 42 subjects. The experimental results show that the described biometric user authentication system is effective, achieving an Equal Error Rate (ERR) of 0.024.

  14. Genetic attack on neural cryptography

    International Nuclear Information System (INIS)

    Ruttor, Andreas; Kinzel, Wolfgang; Naeh, Rivka; Kanter, Ido

    2006-01-01

    Different scaling properties for the complexity of bidirectional synchronization and unidirectional learning are essential for the security of neural cryptography. Incrementing the synaptic depth of the networks increases the synchronization time only polynomially, but the success of the geometric attack is reduced exponentially and it clearly fails in the limit of infinite synaptic depth. This method is improved by adding a genetic algorithm, which selects the fittest neural networks. The probability of a successful genetic attack is calculated for different model parameters using numerical simulations. The results show that scaling laws observed in the case of other attacks hold for the improved algorithm, too. The number of networks needed for an effective attack grows exponentially with increasing synaptic depth. In addition, finite-size effects caused by Hebbian and anti-Hebbian learning are analyzed. These learning rules converge to the random walk rule if the synaptic depth is small compared to the square root of the system size

  15. Genetic attack on neural cryptography

    Science.gov (United States)

    Ruttor, Andreas; Kinzel, Wolfgang; Naeh, Rivka; Kanter, Ido

    2006-03-01

    Different scaling properties for the complexity of bidirectional synchronization and unidirectional learning are essential for the security of neural cryptography. Incrementing the synaptic depth of the networks increases the synchronization time only polynomially, but the success of the geometric attack is reduced exponentially and it clearly fails in the limit of infinite synaptic depth. This method is improved by adding a genetic algorithm, which selects the fittest neural networks. The probability of a successful genetic attack is calculated for different model parameters using numerical simulations. The results show that scaling laws observed in the case of other attacks hold for the improved algorithm, too. The number of networks needed for an effective attack grows exponentially with increasing synaptic depth. In addition, finite-size effects caused by Hebbian and anti-Hebbian learning are analyzed. These learning rules converge to the random walk rule if the synaptic depth is small compared to the square root of the system size.

  16. Cryptography with chaos and shadowing

    Energy Technology Data Exchange (ETDEWEB)

    Smaoui, Nejib [Department of Mathematics and Computer Science, Kuwait University, P.O. Box 5969, Safat 13060 (Kuwait)], E-mail: nsmaoui64@yahoo.com; Kanso, Ali [Department of Mathematics and Computer Science, Kuwait University, P.O. Box 5969, Safat 13060 (Kuwait)], E-mail: akanso@hotmail.com

    2009-11-30

    In this paper, we present a novel approach to encrypt a message (a text composed by some alphabets) using chaos and shadowing. First, we generate a numerical chaotic orbit based on the logistic map, and use the shadowing algorithm of Smaoui and Kostelich [Smaoui N, Kostelich E. Using chaos to shadow the quadratic map for all time. Int J Comput Math 1998;70:117-29] to show that there exists a finite number of true orbits that shadow the numerical orbit. Then, the finite number of maps generated is used in Baptista's algorithm [Baptista MS. Cryptography with chaos. Phys Lett A 1998;240:50-4] to encrypt each character of the message. It is shown that the use of chaos and shadowing in the encryption process enhances the security level.

  17. Quantum Entropy and Its Applications to Quantum Communication and Statistical Physics

    Directory of Open Access Journals (Sweden)

    Masanori Ohya

    2010-05-01

    Full Text Available Quantum entropy is a fundamental concept for quantum information recently developed in various directions. We will review the mathematical aspects of quantum entropy (entropies and discuss some applications to quantum communication, statistical physics. All topics taken here are somehow related to the quantum entropy that the present authors have been studied. Many other fields recently developed in quantum information theory, such as quantum algorithm, quantum teleportation, quantum cryptography, etc., are totally discussed in the book (reference number 60.

  18. Quantum mechanics

    International Nuclear Information System (INIS)

    Basdevant, J.L.; Dalibard, J.; Joffre, M.

    2008-01-01

    All physics is quantum from elementary particles to stars and to the big-bang via semi-conductors and chemistry. This theory is very subtle and we are not able to explain it without the help of mathematic tools. This book presents the principles of quantum mechanics and describes its mathematical formalism (wave function, Schroedinger equation, quantum operators, spin, Hamiltonians, collisions,..). We find numerous applications in the fields of new technologies (maser, quantum computer, cryptography,..) and in astrophysics. A series of about 90 exercises with their answers is included. This book is based on a physics course at a graduate level. (A.C.)

  19. Vortex instability in turbulent free-space propagation

    Science.gov (United States)

    Lavery, Martin P. J.

    2018-04-01

    The spatial structuring of optical fields is integral within many next generation optical metrology and communication techniques. A verifiable physical model of the propagation of these optical fields in a turbulent environment is important for developing effective mitigation techniques for the modal degradation that occurs in a free-space link. We present a method to simulate this modal degradation that agrees with recently reported experimental findings. A 1.5 km free-space link is emulated by decomposing the optical turbulence that accumulates over a long distance link, into many, weakly perturbing steps of 10 m. This simulation shows that the high-order vortex at the centre of the helical phase profiles in modes that carry orbital angular momentum of | {\\ell }| ≥slant 2{\\hslash } are unstable and fracture into many vortices when they propagate over the link. This splitting presents issues for the application of turbulence mitigation techniques. The usefulness of pre-correction, post-correction, and complex field conjugation techniques are discussed.

  20. Robust free-space optical communication for indoor information environment

    Science.gov (United States)

    Nakada, Toyohisa; Itoh, Hideo; Kunifuji, Susumu; Nakashima, Hideyuki

    2003-10-01

    The purpose of our study is to establish a robust communication, while keeping security and privacy, between a handheld communicator and the surrounding information environment. From the viewpoint of low power consumption, we have been developing a reflectivity modulating communication module composed of a liquid crystal light modulator and a corner-reflecting mirror sheet. We installed a corner-reflecting sheet instead of light scattering sheet in a handheld videogame machine with a display screen with a reflection-type liquid crystal. Infrared (IR) LED illuminator attached next to the IR camera of a base station illuminates all the room, and the terminal send their data to the base station by switching ON and OFF of the reflected IR beam. Intensity of reflected light differs with the position and the direction of the terminal, and sometimes the intensity of OFF signal at a certain condition is brighter than that of ON signal at another condition. To improve the communication quality, use of machine learning technique is a possibility of the solution. In this paper, we compare various machine learning techniques for the purpose of free space optical communication, and propose a new algorithm that improves the robustness of the data link. Evaluation using an actual free-space communication system is also described.

  1. Computational security of quantum encryption

    NARCIS (Netherlands)

    Alagic, G.; Broadbent, A.; Fefferman, B.; Gagliardoni, T.; Schaffner, C.; St. Jules, M.; Nascimento, A.C.A.; Barreto, P.

    2016-01-01

    Quantum-mechanical devices have the potential to transform cryptography. Most research in this area has focused either on the information-theoretic advantages of quantum protocols or on the security of classical cryptographic schemes against quantum attacks. In this work, we initiate the study of

  2. Intensity position modulation for free-space laser communication system

    Science.gov (United States)

    Jangjoo, Alireza; Faghihi, F.

    2004-12-01

    In this research a novel modulation technique for free-space laser communication system called Intensity Position Modulation (IPM) is carried out. According to TEM00 mode of a laser beam and by linear fitting on the Gaussian function as an approximation, the variation of linear part on the reverse biased pn photodiode produced alternating currents which contain the information. Here, no characteristic property of the beam as intensity or frequency is changed and only the beam position moves laterally. We demonstrated that in this method no bandwidth is required, so it is possible to reduce the background radiation noise by narrowband filtering of the carrier. The fidelity of the analog voice communication system which is made upon the IPM is satisfactory and we are able to transmit the audio signals up to 1Km.

  3. Initial alignment method for free space optics laser beam

    Science.gov (United States)

    Shimada, Yuta; Tashiro, Yuki; Izumi, Kiyotaka; Yoshida, Koichi; Tsujimura, Takeshi

    2016-08-01

    The authors have newly proposed and constructed an active free space optics transmission system. It is equipped with a motor driven laser emitting mechanism and positioning photodiodes, and it transmits a collimated thin laser beam and accurately steers the laser beam direction. It is necessary to introduce the laser beam within sensible range of the receiver in advance of laser beam tracking control. This paper studies an estimation method of laser reaching point for initial laser beam alignment. Distributed photodiodes detect laser luminescence at respective position, and the optical axis of laser beam is analytically presumed based on the Gaussian beam optics. Computer simulation evaluates the accuracy of the proposed estimation methods, and results disclose that the methods help us to guide the laser beam to a distant receiver.

  4. Hyperon interaction in free space and nuclear matter

    Energy Technology Data Exchange (ETDEWEB)

    Dhar, Madhumita; Lenske, Horst [Institute for Theoretical Physics, Justus- Liebig-University Giessen (Germany)

    2015-07-01

    Baryon-baryon interactions within the SU(3)-octet are investigated in free space and nuclear matter.A meson exchange model based on SU(3) symmetry is used for determining the interaction. The Bethe-Salpeter equations are solved in a 3-D reduction scheme. In-medium effect has been incorporated by including a two particle Pauli projector operator in the scattering equation. The coupling of the various channels of total strangeness S and conserved total charge is studied in detail. Special attention is paid to the physical thresholds. The density dependence of interaction is clearly seen in the variation of the in-medium low-energy parameters. The approach is compared to descriptions derived from chiral-EFT and other meson-exchange models e.g. the Nijmegen and the Juelich model.

  5. Hyperon interaction in free space and nuclear matter

    Energy Technology Data Exchange (ETDEWEB)

    Dhar, Madhumita [Justus-Liebig University Giessen (Germany); Lenske, Horst [Justus-Liebig University Giessen (Germany); GSI, Darmstadt (Germany)

    2016-07-01

    A new approach to the SU(3) flavour symmetric meson-exchange model is introduced to describe free space baryon-baryon interaction. The Bethe-Salpeter equations are solved in a 3-D reduction scheme. The coupling of the various channels of total strangeness S and conserved total charge Q is studied in detail. Special attention is paid to the physical thresholds. The derived vacuum interaction has then been used to derive nuclear medium effect by employing the Pauli projector operator in 3-D reduced Bethe-Salpeter equation. The in-medium properties of the interaction are clearly seen in the variation of the in-medium low-energy parameters as a function of density.

  6. Advanced free space optics (FSO) a systems approach

    CERN Document Server

    Majumdar, Arun K

    2015-01-01

    This book provides a comprehensive, unified tutorial covering the most recent advances in the technology of free-space optics (FSO). It is an all-inclusive source of information on the fundamentals of FSO as well as up-to-date information on the state-of-the-art in technologies available today. This text is intended for graduate students, and will also be useful for research scientists and engineers with an interest in the field. FSO communication is a practical solution for creating a three dimensional global broadband communications grid, offering bandwidths far beyond what is possible in the Radio Frequency (RF) range. However, the attributes of atmospheric turbulence and scattering impose perennial limitations on availability and reliability of FSO links. From a systems point-of-view, this groundbreaking book provides a thorough understanding of channel behavior, which can be used to design and evaluate optimum transmission techniques that operate under realistic atmospheric conditions. Topics addressed...

  7. Indoor Free Space Optic: a new prototype, realization and evaluation

    Science.gov (United States)

    Bouchet, Olivier; Besnard, Pascal; Mihaescu, Adrian

    2008-08-01

    The Free Space Optic (FSO) communication is a daily reality used by an increasing number of companies. For indoor environment, optical wireless communication becomes a good alternative with respect to radio proposals. For both technologies, the architecture is similar: emission/reception base station (Gateway or Bridge) are installed to cover zones, which are defined to ensure a quality of service. The customers may be connected to the Wireless Local Area Network (WLAN) with an adapter or module that emits and receives on this network. But due to its specific characteristics, wireless optical technology could present important advantages such as: Transmitted data security, medical immunity, high data rate, etc... Nevertheless, the optical system may have a limit on the network management aspect and link budget. The scope of this paper is to present a proposal at crossroads between optical fibre telecom system and data processing. In this document, we will present a prototype developed in Brittany during a regional collaborative project (Techim@ges). In order to answer to the management aspect and the link budget, this prototype uses an optical multiplexing technique in 1550 nm band: the Wavelength Division Multiple Access (WDMA). Moreover it also proposes a new class 1 high power emission solution. This full duplex system transmits these various wavelengths in free space, by using optical Multiplexer/Demultiplexer and optical modules. Each module has a defined and personal wavelength associated to the terminal identification (addresses MAC or IP). This approach permits a data rate at a minimum of a ten's Mbit/s per customer and potentially hundred Mbps for a line of sight system. The application field for the achieved and proposed prototype is potentially investigated from WLAN to WPAN.

  8. Neural Network Approach to Locating Cryptography in Object Code

    Energy Technology Data Exchange (ETDEWEB)

    Jason L. Wright; Milos Manic

    2009-09-01

    Finding and identifying cryptography is a growing concern in the malware analysis community. In this paper, artificial neural networks are used to classify functional blocks from a disassembled program as being either cryptography related or not. The resulting system, referred to as NNLC (Neural Net for Locating Cryptography) is presented and results of applying this system to various libraries are described.

  9. China demonstrates intercontinental quantum key distribution

    Science.gov (United States)

    Johnston, Hamish

    2017-11-01

    A quantum cryptography key has been shared between Beijing and Vienna using a satellite - allowing the presidents of the Chinese Academy of Sciences and Austrian Academy of Sciences to communicate via a secure video link.

  10. The development of the room temperature LWIR HgCdTe detectors for free space optics communication systems

    Science.gov (United States)

    Martyniuk, Piotr; Gawron, Waldemar; Mikołajczyk, Janusz

    2017-10-01

    There are many room temperature applications to include free space optics (FSO) communication system combining quantum cascade lasers sources where HgCdTe long-wave (8-12 micrometer) infrared radiation (LWIR) detector reaching ultrafast response time 109 cmHz1/2/W. Since commercially available FSO could operate separately in SWIR, MWIR and LWIR range - the dual band detectors should be implemented into FSO. This paper shows theoretical performance of the dual band back-to-back MWIR and LWIR HgCdTe detector operating at 300 K pointing out the MWIR active layer influence on LWIR operating regime.

  11. Color extended visual cryptography using error diffusion.

    Science.gov (United States)

    Kang, InKoo; Arce, Gonzalo R; Lee, Heung-Kyu

    2011-01-01

    Color visual cryptography (VC) encrypts a color secret message into n color halftone image shares. Previous methods in the literature show good results for black and white or gray scale VC schemes, however, they are not sufficient to be applied directly to color shares due to different color structures. Some methods for color visual cryptography are not satisfactory in terms of producing either meaningless shares or meaningful shares with low visual quality, leading to suspicion of encryption. This paper introduces the concept of visual information pixel (VIP) synchronization and error diffusion to attain a color visual cryptography encryption method that produces meaningful color shares with high visual quality. VIP synchronization retains the positions of pixels carrying visual information of original images throughout the color channels and error diffusion generates shares pleasant to human eyes. Comparisons with previous approaches show the superior performance of the new method.

  12. Increasing complexity with quantum physics.

    Science.gov (United States)

    Anders, Janet; Wiesner, Karoline

    2011-09-01

    We argue that complex systems science and the rules of quantum physics are intricately related. We discuss a range of quantum phenomena, such as cryptography, computation and quantum phases, and the rules responsible for their complexity. We identify correlations as a central concept connecting quantum information and complex systems science. We present two examples for the power of correlations: using quantum resources to simulate the correlations of a stochastic process and to implement a classically impossible computational task.

  13. Quantum correlations in multipartite quantum systems

    Science.gov (United States)

    Jafarizadeh, M. A.; Heshmati, A.; Karimi, N.; Yahyavi, M.

    2018-03-01

    Quantum entanglement is the most famous type of quantum correlation between elements of a quantum system that has a basic role in quantum communication protocols like quantum cryptography, teleportation and Bell inequality detection. However, it has already been shown that various applications in quantum information theory do not require entanglement. Quantum discord as a new kind of quantum correlations beyond entanglement, is the most popular candidate for general quantum correlations. In this paper, first we find the entanglement witness in a particular multipartite quantum system which consists of a N-partite system in 2 n -dimensional space. Then we give an exact analytical formula for the quantum discord of this system. At the end of the paper, we investigate the additivity relation of the quantum correlation and show that this relation is satisfied for a N-partite system with 2 n -dimensional space.

  14. Practical Leakage-Resilient Symmetric Cryptography

    DEFF Research Database (Denmark)

    Faust, Sebastian; Pietrzak, Krzysztof; Schipper, Joachim

    2012-01-01

    Leakage resilient cryptography attempts to incorporate side-channel leakage into the black-box security model and designs cryptographic schemes that are provably secure within it. Informally, a scheme is leakage-resilient if it remains secure even if an adversary learns a bounded amount of arbitr......Leakage resilient cryptography attempts to incorporate side-channel leakage into the black-box security model and designs cryptographic schemes that are provably secure within it. Informally, a scheme is leakage-resilient if it remains secure even if an adversary learns a bounded amount...

  15. Coding and cryptography synergy for a robust communication

    CERN Document Server

    Zivic, Natasa

    2013-01-01

    This book presents the benefits of the synergetic effect of the combination of coding and cryptography. It introduces new directions for the interoperability between the components of a communication system. Coding and cryptography are standard components in today's distributed systems. The integration of cryptography into coding aspects is very interesting, as the usage of cryptography will be common use, even in industrial applications. The book is based on new developments of coding and cryptography, which use real numbers to express reliability values of bits instead of binary values 0 and 1. The presented methods are novel and designed for noisy communication, which doesn´t allow the successful use of cryptography. The rate of successful verifications is improved essentially not only for standard or "hard" verification, but even more after the introduction of "soft" verification. A security analysis shows the impact on the security. Information security and cryptography follow the late developments of c...

  16. Overcoming black body radiation limit in free space: metamaterial superemitter

    Science.gov (United States)

    Maslovski, Stanislav I.; Simovski, Constantin R.; Tretyakov, Sergei A.

    2016-01-01

    Here, we demonstrate that the power spectral density of thermal radiation at a specific wavelength produced by a body of finite dimensions set up in free space under a fixed temperature could be made theoretically arbitrary high, if one could realize double negative metamaterials with arbitrary small loss and arbitrary high absolute values of permittivity and permeability (at a given frequency). This result refutes the widespread belief that Planck’s law itself sets a hard upper limit on the spectral density of power emitted by a finite macroscopic body whose size is much greater than the wavelength. Here we propose a physical realization of a metamaterial emitter whose spectral emissivity can be greater than that of the ideal black body under the same conditions. Due to the reciprocity between the heat emission and absorption processes such cooled down superemitter also acts as an optimal sink for the thermal radiation—the ‘thermal black hole’—which outperforms Kirchhoff-Planck’s black body which can absorb only the rays directly incident on its surface. The results may open a possibility to realize narrowband super-Planckian thermal radiators and absorbers for future thermo-photovoltaic systems and other devices.

  17. Free-space wavelength-multiplexed optical scanner demonstration.

    Science.gov (United States)

    Yaqoob, Zahid; Riza, Nabeel A

    2002-09-10

    Experimental demonstration of a no-moving-parts free-space wavelength-multiplexed optical scanner (W-MOS) is presented. With fast tunable lasers or optical filters and planar wavelength dispersive elements such as diffraction gratings, this microsecond-speed scanner enables large several-centimeter apertures for subdegree angular scans. The proposed W-MOS design incorporates a unique optical amplifier and variable optical attenuator combination that enables the calibration and modulation of the scanner response, leading to any desired scanned laser beam power shaping. The experimental setup uses a tunable laser centered at 1560 nm and a 600-grooves/mm blazed reflection grating to accomplish an angular scan of 12.92 degrees as the source is tuned over an 80-nm bandwidth. The values for calculated maximum optical beam divergance, required wavelength resolution, beam-pointing accuracy, and measured scanner insertion loss are 1.076 mrad, 0.172 nm, 0.06 mrad, and 4.88 dB, respectively.

  18. Novel Photon-Counting Detectors for Free-Space Communication

    Science.gov (United States)

    Krainak, Michael A.; Yang, Guan; Sun, Xiaoli; Lu, Wei; Merritt, Scott; Beck, Jeff

    2016-01-01

    We present performance data for novel photon counting detectors for free space optical communication. NASA GSFC is testing the performance of three novel photon counting detectors 1) a 2x8 mercury cadmium telluride avalanche array made by DRS Inc. 2) a commercial 2880 silicon avalanche photodiode array and 3) a prototype resonant cavity silicon avalanche photodiode array. We will present and compare dark count, photon detection efficiency, wavelength response and communication performance data for these detectors. We discuss system wavelength trades and architectures for optimizing overall communication link sensitivity, data rate and cost performance. The HgCdTe APD array has photon detection efficiencies of greater than 50 were routinely demonstrated across 5 arrays, with one array reaching a maximum PDE of 70. High resolution pixel-surface spot scans were performed and the junction diameters of the diodes were measured. The junction diameter was decreased from 31 m to 25 m resulting in a 2x increase in e-APD gain from 470 on the 2010 array to 1100 on the array delivered to NASA GSFC. Mean single photon SNRs of over 12 were demonstrated at excess noise factors of 1.2-1.3.The commercial silicon APD array has a fast output with rise times of 300ps and pulse widths of 600ps. Received and filtered signals from the entire array are multiplexed onto this single fast output. The prototype resonant cavity silicon APD array is being developed for use at 1 micron wavelength.

  19. Information Theoretical Limits of Free-Space Optical Links

    KAUST Repository

    Ansari, Imran Shafique

    2016-08-25

    Generalized fading has been an imminent part and parcel of wireless communications. It not only characterizes the wireless channel appropriately but also allows its utilization for further performance analysis of various types of wireless communication systems. Under the umbrella of generalized fading channels, a unified ergodic capacity analysis of a free-space optical (FSO) link under both types of detection techniques (i.e., intensity modulation/direct detection (IM/DD) as well as heterodyne detection) over generalized atmospheric turbulence channels that account for generalized pointing errors is presented. Specifically, unified exact closed-form expressions for the moments of the end-to-end signal-to-noise ratio (SNR) of a single link FSO transmission system are presented. Subsequently, capitalizing on these unified statistics, unified exact closed-form expressions for ergodic capacity performance metric of FSO link transmission systems is offered. Additionally, for scenarios wherein the exact closed-form solution is not possible to obtain, some asymptotic results are derived in the high SNR regime. All the presented results are verified via computer-based Monte-Carlo simulations.

  20. Free Space Optics – Monitoring Setup for Experimental Link

    Directory of Open Access Journals (Sweden)

    Ján Tóth

    2015-12-01

    Full Text Available This paper deals with advanced Free Space Optics communication technology. Two FSO nodes are needed in order to make a connection. Laser diodes are used as light sources. Simple OOK modulation is involved in this technology. FSO system offers multiple advantages indeed. However, a direct visibility is required in order to set up a communication link. This fact yields perhaps the most significant weakness of this technology. Obviously, there is no a chance to fight the weather phenomena like fog, heavy rain, dust and many other particles which are naturally present in the atmosphere. That’s why there is a key task to find a suitable solution to keep FSO link working with high reliability and availability. It turns out that it’s necessary to have knowledge about weather situation when FSO link operates (liquid water content - LWC, geographical location, particle size distribution, average particle diameter, temperature, humidity, wind conditions, pressure and many other variable weather parameters. It’s obvious that having most of mentioned parameter’s values stored in database (implicitly in charts would be really beneficial. This paper presents some of mentioned indicators continuously gathered from several sensors located close to one of FSO nodes.

  1. Overcoming black body radiation limit in free space: metamaterial superemitter

    International Nuclear Information System (INIS)

    Maslovski, Stanislav I; Simovski, Constantin R; Tretyakov, Sergei A

    2016-01-01

    Here, we demonstrate that the power spectral density of thermal radiation at a specific wavelength produced by a body of finite dimensions set up in free space under a fixed temperature could be made theoretically arbitrary high, if one could realize double negative metamaterials with arbitrary small loss and arbitrary high absolute values of permittivity and permeability (at a given frequency). This result refutes the widespread belief that Planck’s law itself sets a hard upper limit on the spectral density of power emitted by a finite macroscopic body whose size is much greater than the wavelength. Here we propose a physical realization of a metamaterial emitter whose spectral emissivity can be greater than that of the ideal black body under the same conditions. Due to the reciprocity between the heat emission and absorption processes such cooled down superemitter also acts as an optimal sink for the thermal radiation—the ‘thermal black hole’—which outperforms Kirchhoff–Planck’s black body which can absorb only the rays directly incident on its surface. The results may open a possibility to realize narrowband super-Planckian thermal radiators and absorbers for future thermo-photovoltaic systems and other devices. (paper)

  2. Optical Axis Identification Technique for Free Space Optics Transmission

    Directory of Open Access Journals (Sweden)

    Yuki Tashiro

    2017-07-01

    Full Text Available This paper describes optical axis adjustment technique for an active free space optics transmission system. This system precisely controls the direction of a collimated thin laser beam using a motor driven laser emitting mechanism and positioning photodiodes. Before beginning laser beam feedback control, it is required to guide the laser beam within the range of the positioning photodiodes for initial laser beam alignment. This paper proposes an arrival position presumption method of laser beam traveling along the long distance from transmitter. A positioning sensor containing several photodiodes measures laser luminescence distribution, and analytically calculates the optical axis of laser beam according to the modified Gaussian beam optics based on four or five distributed local intensity of laser luminescence. Experiments are conducted to evaluate the accuracy of the presumption, and results reveal that the method is effective in leading the laser beam onto a distant receiver.

  3. Free-space optical channel characterization in a coastal environment

    KAUST Repository

    Alheadary, Wael Ghazy

    2017-12-28

    Recently, FSO (Free-Space Optical Communication) has received a lot of attention thanks to its high data-rate transmission via unbounded unlicensed bandwidth. However, some weather conditions lead to significant degradation of the FSO link performance. Based on this context and in order to have a better understanding of the capabilities of FSO communication in a coastal environment, the effects of temperature and humidity on an FSO system are investigated in this study. An experiment is conducted using an open source FSO system that achieves a transmission rate of 1 Gbit/s at a distance of 70 m. Two new mathematical models are proposed to represent the effects of temperature and humidity on our developed FSO system operating at a wavelength of 1 550 nm. The first model links the FSO attenuation coeffcient to the air temperature in coastal regions, while the second model links the FSO attenuation coeffcient to the humidity and the dew-point temperature. The key finding of this study is that FSO links can achieve maximum availability in a coastal city with normal variations in temperature and humidity.

  4. Designing localized electromagnetic fields in a source-free space

    International Nuclear Information System (INIS)

    Borzdov, George N.

    2002-01-01

    An approach to characterizing and designing localized electromagnetic fields, based on the use of differentiable manifolds, differentiable mappings, and the group of rotation, is presented. By way of illustration, novel families of exact time-harmonic solutions to Maxwell's equations in the source-free space - localized fields defined by the rotation group - are obtained. The proposed approach provides a broad spectrum of tools to design localized fields, i.e., to build-in symmetry properties of oscillating electric and magnetic fields, to govern the distributions of their energy densities (both size and form of localization domains), and to set the structure of time-average energy fluxes. It is shown that localized fields can be combined as constructive elements to obtain a complex field structure with desirable properties, such as one-, two-, or three-dimensional field gratings. The proposed approach can be used in designing localized electromagnetic fields to govern motion and state of charged and neutral particles. As an example, motion of relativistic electrons in one-dimensional and three-dimensional field gratings is treated

  5. Introduction to quantum information science

    CERN Document Server

    Hayashi, Masahito; Kawachi, Akinori; Kimura, Gen; Ogawa, Tomohiro

    2015-01-01

    This book presents the basics of quantum information, e.g., foundation of quantum theory, quantum algorithms, quantum entanglement, quantum entropies, quantum coding, quantum error correction and quantum cryptography. The required knowledge is only elementary calculus and linear algebra. This way the book can be understood by undergraduate students. In order to study quantum information, one usually has to study the foundation of quantum theory. This book describes it from more an operational viewpoint which is suitable for quantum information while traditional textbooks of quantum theory lack this viewpoint. The current  book bases on Shor's algorithm, Grover's algorithm, Deutsch-Jozsa's algorithm as basic algorithms. To treat several topics in quantum information, this book covers several kinds of information quantities in quantum systems including von Neumann entropy. The limits of several kinds of quantum information processing are given. As important quantum protocols,this book contains quantum teleport...

  6. Opportunities in white-box cryptography

    NARCIS (Netherlands)

    Michiels, W.

    White-box cryptography is the discipline of implementing a cryptographic algorithm in software such that an adversary will have difficulty extracting the cryptographic key. This approach assumes that the adversary has full access to and full control over the implementation's execution. White-box

  7. Privacy-Enhancing Auctions Using Rational Cryptography

    DEFF Research Database (Denmark)

    Miltersen, Peter Bro; Nielsen, Jesper Buus; Triandopoulos, Nikolaos

    2009-01-01

    show how to use rational cryptography to approximately implement any given ex interim individually strictly rational equilibrium of such an auction without a trusted mediator through a cryptographic protocol that uses only point-to-point authenticated channels between the players. By “ex interim...

  8. Report on Pairing-based Cryptography.

    Science.gov (United States)

    Moody, Dustin; Peralta, Rene; Perlner, Ray; Regenscheid, Andrew; Roginsky, Allen; Chen, Lily

    2015-01-01

    This report summarizes study results on pairing-based cryptography. The main purpose of the study is to form NIST's position on standardizing and recommending pairing-based cryptography schemes currently published in research literature and standardized in other standard bodies. The report reviews the mathematical background of pairings. This includes topics such as pairing-friendly elliptic curves and how to compute various pairings. It includes a brief introduction to existing identity-based encryption (IBE) schemes and other cryptographic schemes using pairing technology. The report provides a complete study of the current status of standard activities on pairing-based cryptographic schemes. It explores different application scenarios for pairing-based cryptography schemes. As an important aspect of adopting pairing-based schemes, the report also considers the challenges inherent in validation testing of cryptographic algorithms and modules. Based on the study, the report suggests an approach for including pairing-based cryptography schemes in the NIST cryptographic toolkit. The report also outlines several questions that will require further study if this approach is followed.

  9. Harry Potter and the Cryptography with Matrices

    Science.gov (United States)

    Chua, Boon Liang

    2006-01-01

    This article describes Cryptography, defined as the science of encrypting and deciphering messages written in secret codes, it has played a vital role in securing information since ancient times. There are several cryptographic techniques and many make extensive use of mathematics to secure information. The author discusses an activity built…

  10. Number Theory and Public-Key Cryptography.

    Science.gov (United States)

    Lefton, Phyllis

    1991-01-01

    Described are activities in the study of techniques used to conceal the meanings of messages and data. Some background information and two BASIC programs that illustrate the algorithms used in a new cryptographic system called "public-key cryptography" are included. (CW)

  11. Is Calculus a Failure in Cryptography?

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 21; Issue 3. Is Calculus a Failure in Cryptography? P Vanchinathan. General Article Volume 21 Issue 3 March 2016 pp 239-245. Fulltext. Click here to view fulltext PDF. Permanent link: https://www.ias.ac.in/article/fulltext/reso/021/03/0239-0245. Keywords.

  12. From the atomic nucleus to the cosmos. How the strange laws of the quantum world form our reality

    International Nuclear Information System (INIS)

    Beckers, Mike

    2016-01-01

    The following topics are dealt with: The reality of nature, Hamlet in quantum world, the ene of the local realism, quantum jumps, a new quantum theory, string theory for solids, atomic nuclei between liquid and crystal, simulated quantum worlds, space-time entanglement, Einstein in the quantum test, quantum cryptography, quantum computers as code breaker. (HSI)

  13. Direct longitudinal laser acceleration of electrons in free space

    Directory of Open Access Journals (Sweden)

    Sergio Carbajo

    2016-02-01

    Full Text Available Compact laser-driven accelerators are pursued heavily worldwide because they make novel methods and tools invented at national laboratories widely accessible in science, health, security, and technology [V. Malka et al., Principles and applications of compact laser-plasma accelerators, Nat. Phys. 4, 447 (2008]. Current leading laser-based accelerator technologies [S. P. D. Mangles et al., Monoenergetic beams of relativistic electrons from intense laser-plasma interactions, Nature (London 431, 535 (2004; T. Toncian et al., Ultrafast laser-driven microlens to focus and energy-select mega-electron volt protons, Science 312, 410 (2006; S. Tokita et al. Single-shot ultrafast electron diffraction with a laser-accelerated sub-MeV electron pulse, Appl. Phys. Lett. 95, 111911 (2009] rely on a medium to assist the light to particle energy transfer. The medium imposes material limitations or may introduce inhomogeneous fields [J. R. Dwyer et al., Femtosecond electron diffraction: “Making the molecular movie,”, Phil. Trans. R. Soc. A 364, 741 (2006]. The advent of few cycle ultraintense radially polarized lasers [S. Carbajo et al., Efficient generation of ultraintense few-cycle radially polarized laser pulses, Opt. Lett. 39, 2487 (2014] has ushered in a novel accelerator concept [L. J. Wong and F. X. Kärtner, Direct acceleration of an electron in infinite vacuum by a pulsed radially polarized laser beam, Opt. Express 18, 25035 (2010; F. Pierre-Louis et al. Direct-field electron acceleration with ultrafast radially polarized laser beams: Scaling laws and optimization, J. Phys. B 43, 025401 (2010; Y. I. Salamin, Electron acceleration from rest in vacuum by an axicon Gaussian laser beam, Phys. Rev. A 73, 043402 (2006; C. Varin and M. Piché, Relativistic attosecond electron pulses from a free-space laser-acceleration scheme, Phys. Rev. E 74, 045602 (2006; A. Sell and F. X. Kärtner, Attosecond electron bunches accelerated and

  14. Fast QC-LDPC code for free space optical communication

    Science.gov (United States)

    Wang, Jin; Zhang, Qi; Udeh, Chinonso Paschal; Wu, Rangzhong

    2017-02-01

    Free Space Optical (FSO) Communication systems use the atmosphere as a propagation medium. Hence the atmospheric turbulence effects lead to multiplicative noise related with signal intensity. In order to suppress the signal fading induced by multiplicative noise, we propose a fast Quasi-Cyclic (QC) Low-Density Parity-Check (LDPC) code for FSO Communication systems. As a linear block code based on sparse matrix, the performances of QC-LDPC is extremely near to the Shannon limit. Currently, the studies on LDPC code in FSO Communications is mainly focused on Gauss-channel and Rayleigh-channel, respectively. In this study, the LDPC code design over atmospheric turbulence channel which is nether Gauss-channel nor Rayleigh-channel is closer to the practical situation. Based on the characteristics of atmospheric channel, which is modeled as logarithmic-normal distribution and K-distribution, we designed a special QC-LDPC code, and deduced the log-likelihood ratio (LLR). An irregular QC-LDPC code for fast coding, of which the rates are variable, is proposed in this paper. The proposed code achieves excellent performance of LDPC codes and can present the characteristics of high efficiency in low rate, stable in high rate and less number of iteration. The result of belief propagation (BP) decoding shows that the bit error rate (BER) obviously reduced as the Signal-to-Noise Ratio (SNR) increased. Therefore, the LDPC channel coding technology can effectively improve the performance of FSO. At the same time, the BER, after decoding reduces with the increase of SNR arbitrarily, and not having error limitation platform phenomenon with error rate slowing down.

  15. Nonequivalence of two flavors of oblivious transfer at the quantum level

    International Nuclear Information System (INIS)

    He Guangping; Wang, Z. D.

    2006-01-01

    Though all-or-nothing oblivious transfer and one-out-of-two oblivious transfer are equivalent in classical cryptography, we here show that a protocol built upon secure quantum all-or-nothing oblivious transfer cannot satisfy the rigorous definition of quantum one-out-of-two oblivious transfer due to the nature of quantum cryptography. Thus the securities of the two oblivious transfer protocols are not equivalent at the quantum level

  16. Plasmonics for emerging quantum technologies

    DEFF Research Database (Denmark)

    Bozhevolnyi, Sergey I.; Mortensen, N. Asger

    2017-01-01

    to exponentially increase computing power, quantum computing opens up possibilities to carry out calculations that ordinary computers could not finish in the lifetime of the Universe, while optical communications based on quantum cryptography become completely secure. At the same time, the emergence of Big Data...

  17. Free space optics: a viable last-mile alternative

    Science.gov (United States)

    Willebrand, Heinz A.; Clark, Gerald R.

    2001-10-01

    This paper explores Free Space Optics (FSO) as an access technology in the last mile of metropolitan area networks (MANs). These networks are based in part on fiber-optic telecommunications infrastructure, including network architectures of Synchronous Optical Network (commonly referred to as SONET), the North American standard for synchronous data transmission; and Synchronous Digital Hierarchy (commonly referred to as SDH), the international standard and equivalent of SONET. Several converging forces have moved FSO beyond a niche technology for use only in local area networks (LANs) as a bridge connecting two facilities. FSO now allows service providers to cost effectively provide optical bandwidth for access networks and accelerate the extension of metro optical networks bridging what has been termed by industry experts as the optical dead zone. The optical dead zone refers to both the slowdown in capital investment in the short-term future and the actual connectivity gap that exists today between core metro optical networks and the access optical networks. Service providers have built extensive core and minimal metro networks but have not yet provided optical bandwidth to the access market largely due to the non-compelling economics to bridge the dead zone with fiber. Historically, such infrastructure build-out slowdowns have been blamed on a combination of economics, time-to-market constraints and limited technology options. However, new technology developments and market acceptance of FSO give service providers a new cost-effective alternative to provide high-bandwidth services with optical bandwidth in the access networks. Merrill Lynch predicts FSO will grow into a $2 billion market by 2005. The drivers for this market are a mere 5%- 6% penetration of fiber to business buildings; cost effective solution versus RF or fiber; and significant capacity which can only be matched by a physical fiber link, Merrill Lynch reports. This paper will describe FSO

  18. Robust catastrophe-free space agriculture on Mars

    Science.gov (United States)

    Yamashita, Masamichi

    During the early stage of CELSS research, economy was a selling point of the bio-regenerative life support concept. Until system integration was exercised in detail at mission planing for the International Space Station, the turning point from open system to CELSS was estimated 10 years of operation for 10 crew member as a consensus. Initial investment and operational cost for the 10-10 regenerative system was believed to be cheaper than the integrated amount of consumables for running open system. Any drop-out from recycling loop of materials is counted as “penalty”. Under this context, degree of closure was raised as an index to measure “maturity” of CELSS technology. Once it was found quite difficult to achieve 100 % closure perfect, science merit of CELSS study was redefined as a small scaled model of terrestrial biosphere. Natural ecosystem has huge sink and backyard in its materials loop. They provide a basis for keeping member in the ecology without falling into catastrophe. Low productivity at high biological diversity is a common key feature at the climax phase of ecosystem. Artificial ecosystem on ground relies on “unpaid” backyard function of surrounding biosphere together with strong control for realizing high productivity at less degree of bio-diversity. It should be noted that top criteria in engineering manned space system is robustness and survivability of crew. All other item is secondary, and just better to have. Without verification of catastrophe free, space agriculture will never be implemented for space and stay as a fantasy on ground forever. There is a great gap between ecology and this requirement for manned space system. In order to fill this gap, we should remind how gatherer and hunter was civilized after the agricultural revolution about ten thousand years ago. Planting cereal crop was a great second step in agricultural innovation. Cereal grain can be stored more than one year after its harvest. Food processing and

  19. Free Space Optics for Next Generation Cellular Backhaul

    KAUST Repository

    Zedini, Emna

    2016-11-01

    The exponential increase in the number of mobile users, coupled with the strong demand for high-speed data services results in a significant growth in the required cellular backhaul capacity. Optimizing the cost efficiency while increasing the capacity is becoming a key challenge to the cellular backhaul. It refers to connections between base stations and mobile switching nodes over a variety of transport technologies such as copper, optical fibers, and radio links. These traditional transmission technologies are either expensive, or cannot provide high data rates. This work is focused on the opportunities of free-space-optical (FSO) technology in next generation cellular back- haul. FSO is a cost effective and wide bandwidth solution as compared with the traditional radio-frequency (RF) transmission. Moreover, due to its ease of deployment, license-free operation, high transmission security, and insensitivity to interference, FSO links are becoming an attractive solution for next generation cellular networks. However, the widespread deployment of FSO links is hampered by the atmospheric turbulence-induced fading, weather conditions, and pointing errors. Increasing the reliability of FSO systems, while still exploiting their high data rate communications, is a key requirement in the deployment of an FSO-based backhaul. Therefore, the aim of this work is to provide different approaches to address these technical challenges. In this context, investigation of hybrid automatic repeat request (HARQ) protocols from an information-theoretic perspective is undertaken. Moreover, performance analysis of asymmetric RF/FSO dual-hop systems is studied. In such system models, multiple RF users can be multiplexed and sent over the FSO link. More specifically, the end-to-end performance metrics are presented in closed-form. This also has increased the interest to study the performance of dual-hop mixed FSO/RF systems, where the FSO link is used as a multicast channel that serves

  20. 3 x 3 free-space optical router based on crossbar network and its control algorithm

    Science.gov (United States)

    Hou, Peipei; Sun, Jianfeng; Yu, Zhou; Lu, Wei; Wang, Lijuan; Liu, Liren

    2015-08-01

    A 3 × 3 free-space optical router, which comprises optical switches and polarizing beam splitter (PBS) and based on crossbar network, is proposed in this paper. A control algorithm for the 3 × 3 free-space optical router is also developed to achieve rapid control without rearrangement. In order to test the performance of the network based on 3 × 3 free-space optical router and that of the algorithm developed for the optical router, experiments are designed. The experiment results show that the interconnection network based on the 3 × 3 free-space optical router has low cross talk, fast connection speed. Under the control of the algorithm developed, a non-block and real free interconnection network is obtained based on the 3 × 3 free-space optical router we proposed.

  1. Towards Practical Whitebox Cryptography: Optimizing Efficiency and Space Hardness

    DEFF Research Database (Denmark)

    Bogdanov, Andrey; Isobe, Takanori; Tischhauser, Elmar Wolfgang

    2016-01-01

    Whitebox cryptography aims to provide security for cryptographic algorithms in an untrusted environment where the adversary has full access to their implementation. Typical security goals for whitebox cryptography include key extraction security and decomposition security: Indeed, it should...... the practical requirements to whitebox cryptography in real-world applications such as DRM or mobile payments. Moreover, we formalize resistance towards decomposition in form of weak and strong space hardness at various security levels. We obtain bounds on space hardness in all those adversarial models...... real-world applications with whitebox cryptography....

  2. Quantum tasks in Minkowski space

    International Nuclear Information System (INIS)

    Kent, Adrian

    2012-01-01

    The fundamental properties of quantum information and its applications to computing and cryptography have been greatly illuminated by considering information-theoretic tasks that are provably possible or impossible within non-relativistic quantum mechanics. I describe here a general framework for defining tasks within (special) relativistic quantum theory and illustrate it with examples from relativistic quantum cryptography and relativistic distributed quantum computation. The framework gives a unified description of all tasks previously considered and also defines a large class of new questions about the properties of quantum information in relation to Minkowski causality. It offers a way of exploring interesting new fundamental tasks and applications, and also highlights the scope for a more systematic understanding of the fundamental information-theoretic properties of relativistic quantum theory. (paper)

  3. Cryptography and the Internet: lessons and challenges

    Energy Technology Data Exchange (ETDEWEB)

    McCurley, K.S.

    1996-12-31

    The popularization of the Internet has brought fundamental changes to the world, because it allows a universal method of communication between computers. This carries enormous benefits with it, but also raises many security considerations. Cryptography is a fundamental technology used to provide security of computer networks, and there is currently a widespread engineering effort to incorporate cryptography into various aspects of the Internet. The system-level engineering required to provide security services for the Internet carries some important lessons for researchers whose study is focused on narrowly defined problems. It also offers challenges to the cryptographic research community by raising new questions not adequately addressed by the existing body of knowledge. This paper attempts to summarize some of these lessons and challenges for the cryptographic research community.

  4. Asymmetric cryptography based on wavefront sensing.

    Science.gov (United States)

    Peng, Xiang; Wei, Hengzheng; Zhang, Peng

    2006-12-15

    A system of asymmetric cryptography based on wavefront sensing (ACWS) is proposed for the first time to our knowledge. One of the most significant features of the asymmetric cryptography is that a trapdoor one-way function is required and constructed by analogy to wavefront sensing, in which the public key may be derived from optical parameters, such as the wavelength or the focal length, while the private key may be obtained from a kind of regular point array. The ciphertext is generated by the encoded wavefront and represented with an irregular array. In such an ACWS system, the encryption key is not identical to the decryption key, which is another important feature of an asymmetric cryptographic system. The processes of asymmetric encryption and decryption are formulized mathematically and demonstrated with a set of numerical experiments.

  5. Device-independent two-party cryptography secure against sequential attacks

    Science.gov (United States)

    Kaniewski, Jędrzej; Wehner, Stephanie

    2016-05-01

    The goal of two-party cryptography is to enable two parties, Alice and Bob, to solve common tasks without the need for mutual trust. Examples of such tasks are private access to a database, and secure identification. Quantum communication enables security for all of these problems in the noisy-storage model by sending more signals than the adversary can store in a certain time frame. Here, we initiate the study of device-independent (DI) protocols for two-party cryptography in the noisy-storage model. Specifically, we present a relatively easy to implement protocol for a cryptographic building block known as weak string erasure and prove its security even if the devices used in the protocol are prepared by the dishonest party. DI two-party cryptography is made challenging by the fact that Alice and Bob do not trust each other, which requires new techniques to establish security. We fully analyse the case of memoryless devices (for which sequential attacks are optimal) and the case of sequential attacks for arbitrary devices. The key ingredient of the proof, which might be of independent interest, is an explicit (and tight) relation between the violation of the Clauser-Horne-Shimony-Holt inequality observed by Alice and Bob and uncertainty generated by Alice against Bob who is forced to measure his system before finding out Alice’s setting (guessing with postmeasurement information). In particular, we show that security is possible for arbitrarily small violation.

  6. Device-independent two-party cryptography secure against sequential attacks

    International Nuclear Information System (INIS)

    Kaniewski, Jędrzej; Wehner, Stephanie

    2016-01-01

    The goal of two-party cryptography is to enable two parties, Alice and Bob, to solve common tasks without the need for mutual trust. Examples of such tasks are private access to a database, and secure identification. Quantum communication enables security for all of these problems in the noisy-storage model by sending more signals than the adversary can store in a certain time frame. Here, we initiate the study of device-independent (DI) protocols for two-party cryptography in the noisy-storage model. Specifically, we present a relatively easy to implement protocol for a cryptographic building block known as weak string erasure and prove its security even if the devices used in the protocol are prepared by the dishonest party. DI two-party cryptography is made challenging by the fact that Alice and Bob do not trust each other, which requires new techniques to establish security. We fully analyse the case of memoryless devices (for which sequential attacks are optimal) and the case of sequential attacks for arbitrary devices. The key ingredient of the proof, which might be of independent interest, is an explicit (and tight) relation between the violation of the Clauser–Horne–Shimony–Holt inequality observed by Alice and Bob and uncertainty generated by Alice against Bob who is forced to measure his system before finding out Alice’s setting (guessing with postmeasurement information). In particular, we show that security is possible for arbitrarily small violation. (paper)

  7. Quantum information with Gaussian states

    International Nuclear Information System (INIS)

    Wang Xiangbin; Hiroshima, Tohya; Tomita, Akihisa; Hayashi, Masahito

    2007-01-01

    Quantum optical Gaussian states are a type of important robust quantum states which are manipulatable by the existing technologies. So far, most of the important quantum information experiments are done with such states, including bright Gaussian light and weak Gaussian light. Extending the existing results of quantum information with discrete quantum states to the case of continuous variable quantum states is an interesting theoretical job. The quantum Gaussian states play a central role in such a case. We review the properties and applications of Gaussian states in quantum information with emphasis on the fundamental concepts, the calculation techniques and the effects of imperfections of the real-life experimental setups. Topics here include the elementary properties of Gaussian states and relevant quantum information device, entanglement-based quantum tasks such as quantum teleportation, quantum cryptography with weak and strong Gaussian states and the quantum channel capacity, mathematical theory of quantum entanglement and state estimation for Gaussian states

  8. Introduction to quantum information science

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, Masahito [Nagoya Univ. (Japan). Graduate School of Mathematics; Ishizaka, Satoshi [Hiroshima Univ., Higashi-Hiroshima (Japan). Graduate School of Integrated Arts and Sciences; Kawachi, Akinori [Tokyo Institute of Technology (Japan). Dept. of Mathematical and Computing Sciences; Kimura, Gen [Shibaura Institute of Technology, Saitama (Japan). College of Systems Engineering and Science; Ogawa, Tomohiro [Univ. of Electro-Communications, Tokyo (Japan). Graduate School of Information Systems

    2015-04-01

    Presents the mathematical foundation for quantum information in a very didactic way. Summarizes all required mathematical knowledge in linear algebra. Supports teaching and learning with more than 100 exercises with solutions. Includes brief descriptions to recent results with references. This book presents the basics of quantum information, e.g., foundation of quantum theory, quantum algorithms, quantum entanglement, quantum entropies, quantum coding, quantum error correction and quantum cryptography. The required knowledge is only elementary calculus and linear algebra. This way the book can be understood by undergraduate students. In order to study quantum information, one usually has to study the foundation of quantum theory. This book describes it from more an operational viewpoint which is suitable for quantum information while traditional textbooks of quantum theory lack this viewpoint. The current book bases on Shor's algorithm, Grover's algorithm, Deutsch-Jozsa's algorithm as basic algorithms. To treat several topics in quantum information, this book covers several kinds of information quantities in quantum systems including von Neumann entropy. The limits of several kinds of quantum information processing are given. As important quantum protocols,this book contains quantum teleportation, quantum dense coding, quantum data compression. In particular conversion theory of entanglement via local operation and classical communication are treated too. This theory provides the quantification of entanglement, which coincides with von Neumann entropy. The next part treats the quantum hypothesis testing. The decision problem of two candidates of the unknown state are given. The asymptotic performance of this problem is characterized by information quantities. Using this result, the optimal performance of classical information transmission via noisy quantum channel is derived. Quantum information transmission via noisy quantum channel by quantum error

  9. Introduction to quantum information science

    International Nuclear Information System (INIS)

    Hayashi, Masahito; Ishizaka, Satoshi; Kawachi, Akinori; Kimura, Gen; Ogawa, Tomohiro

    2015-01-01

    Presents the mathematical foundation for quantum information in a very didactic way. Summarizes all required mathematical knowledge in linear algebra. Supports teaching and learning with more than 100 exercises with solutions. Includes brief descriptions to recent results with references. This book presents the basics of quantum information, e.g., foundation of quantum theory, quantum algorithms, quantum entanglement, quantum entropies, quantum coding, quantum error correction and quantum cryptography. The required knowledge is only elementary calculus and linear algebra. This way the book can be understood by undergraduate students. In order to study quantum information, one usually has to study the foundation of quantum theory. This book describes it from more an operational viewpoint which is suitable for quantum information while traditional textbooks of quantum theory lack this viewpoint. The current book bases on Shor's algorithm, Grover's algorithm, Deutsch-Jozsa's algorithm as basic algorithms. To treat several topics in quantum information, this book covers several kinds of information quantities in quantum systems including von Neumann entropy. The limits of several kinds of quantum information processing are given. As important quantum protocols,this book contains quantum teleportation, quantum dense coding, quantum data compression. In particular conversion theory of entanglement via local operation and classical communication are treated too. This theory provides the quantification of entanglement, which coincides with von Neumann entropy. The next part treats the quantum hypothesis testing. The decision problem of two candidates of the unknown state are given. The asymptotic performance of this problem is characterized by information quantities. Using this result, the optimal performance of classical information transmission via noisy quantum channel is derived. Quantum information transmission via noisy quantum channel by quantum error correction are

  10. Gröbner Bases, Coding, and Cryptography

    CERN Document Server

    Sala, Massimiliano; Perret, Ludovic

    2009-01-01

    Coding theory and cryptography allow secure and reliable data transmission, which is at the heart of modern communication. This book offers a comprehensive overview on the application of commutative algebra to coding theory and cryptography. It analyzes important properties of algebraic/geometric coding systems individually.

  11. Characterization of the Marine Atmosphere for Free-Space Optical Communication

    National Research Council Canada - National Science Library

    Thomas, Linda M. Wasiczko; Moore, Christopher I; Burris, Harris R; Suite, Michele; Stell, Mena; Murphy, James; Gilbreath, G. C; Rabinovich, William; Scharpf, William

    2006-01-01

    The Chesapeake Bay Detachment of the Naval Research Laboratory (NRL-CBD) provides an ideal environment for characterizing the effects of the marine atmosphere on free space optical communication links...

  12. On the performance of free-space optical communication systems with multiuser diversity

    KAUST Repository

    Yang, Liang; Gao, Xiqi; Alouini, Mohamed-Slim

    2014-01-01

    Free space optical (FSO) communication has become a cost-effective method to provide high data rates. However, the turbulence-induced fading limits its application to short range applications. To address this, we propose a multiuser diversity (MD

  13. Encoding information using Laguerre Gaussian modes over free space turbulence media

    CSIR Research Space (South Africa)

    Trichili, A

    2016-07-01

    Full Text Available of the atmospheric turbulence on the proposed communication system. We believe that the proposed technique is promising for high-bit-rate spatial division multiplexing in optical fiber and free space communication systems....

  14. Development of the Free-space Optical Communications Analysis Software (FOCAS)

    Science.gov (United States)

    Jeganathan, M.; Mecherle, G.; Lesh, J.

    1998-01-01

    The Free-space Optical Communications Analysis Software (FOCAS) was developed at the Jet Propulsion Laboratory (JPL) to provide mission planners, systems engineers and communications engineers with an easy to use tool to analyze optical communications link.

  15. Performance of Cat's Eye Modulating Retro-Reflectors for Free-Space Optical Communications

    National Research Council Canada - National Science Library

    Rabinovich, W. S; Goetz, P. G; Mahon, R; Swingen, L; Murphy, J; Gilbreath, G. C; Binari, S; Waluschka, E

    2004-01-01

    Modulating retro-reflectors (MRR) couple passive optical retro-reflectors with electro-optic modulators to allow free-space optical communication with a laser and pointing/acquisition/tracking system required on only one end of the link...

  16. Resilient backhaul network design using hybrid radio/free-space optical technology

    KAUST Repository

    Douik, Ahmed; Dahrouj, Hayssam; Al-Naffouri, Tareq Y.; Alouini, Mohamed-Slim

    2016-01-01

    The radio-frequency (RF) technology is a scalable solution for the backhaul planning. However, its performance is limited in terms of data rate and latency. Free Space Optical (FSO) backhaul, on the other hand, offers a higher data rate

  17. Ergodic Capacity Analysis of Free-Space Optical Links with Nonzero Boresight Pointing Errors

    KAUST Repository

    Ansari, Imran Shafique; Alouini, Mohamed-Slim; Cheng, Julian

    2015-01-01

    A unified capacity analysis of a free-space optical (FSO) link that accounts for nonzero boresight pointing errors and both types of detection techniques (i.e. intensity modulation/ direct detection as well as heterodyne detection) is addressed

  18. Unified performance analysis of hybrid-ARQ with incremental redundancy over free-space optical channels

    KAUST Repository

    Zedini, Emna; Chelli, Ali; Alouini, Mohamed-Slim

    2014-01-01

    In this paper, we carry out a unified performance analysis of hybrid automatic repeat request (HARQ) with incremental redundancy (IR) from an information theoretic perspective over a point-to-point free-space optical (FSO) system. First, we

  19. Multimode entanglement assisted QKD through a free-space maritime channel

    Science.gov (United States)

    Gariano, John; Djordjevic, Ivan B.

    2017-10-01

    When using quantum key distribution (QKD), one of the trade-offs for security is that the generation rate of a secret key is typically very low. Recent works have shown that using a weak coherent source allows for higher secret key generation rates compared to an entangled photon source, when a channel with low loss is considered. In most cases, the system that is being studied is over a fiber-optic communication channel. Here a theoretical QKD system using the BB92 protocol and entangled photons over a free-space maritime channel with multiple spatial modes is presented. The entangled photons are generated from a spontaneous parametric down conversion (SPDC) source of type II. To employ multiple spatial modes, the transmit apparatus will contain multiple SPDC sources, all driven by the pump lasers assumed to have the same intensity. The receive apparatuses will contain avalanche photo diodes (APD), modeled based on the NuCrypt CPDS-1000 detector, and located at the focal point of the receive aperture lens. The transmitter is assumed to be located at Alice and Bob will be located 30 km away, implying no channel crosstalk will be introduced in the measurements at Alice's side due to turbulence. To help mitigate the effects of atmospheric turbulence, adaptive optics will be considered at the transmitter and the receiver. An eavesdropper, Eve, is located 15 km from Alice and has no control over the devices at Alice or Bob. Eve is performing the intercept resend attack and listening to the communication over the public channel. Additionally, it is assumed that Eve can correct any aberrations caused by the atmospheric turbulence to determine which source the photon was transmitted from. One, four and nine spatial modes are considered with and without applying adaptive optics and compared to one another.

  20. Correlation of free-space optics link attenuation with sonic temperature

    Czech Academy of Sciences Publication Activity Database

    Chládová, Zuzana; Fišer, Ondřej; Brázda, Vladimír; Svoboda, Jaroslav

    2013-01-01

    Roč. 52, č. 3 (2013) ISSN 0091-3286 R&D Projects: GA ČR(CZ) GAP102/11/1376 Institutional support: RVO:68378289 Keywords : free-space optics * atmospheric attenuation * water vapor * free-space optics design Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 0.958, year: 2013 http://opticalengineering.spiedigitallibrary.org/article.aspx?articleid=1667062

  1. A review on channel models in free space optical communication systems

    Science.gov (United States)

    Anbarasi, K.; Hemanth, C.; Sangeetha, R. G.

    2017-12-01

    Free Space Optical communication (FSO) is a wireless communication technology which uses light to transmit the data in free space. FSO has advantages like unlicensed spectrum and higher bandwidth. In this paper FSO system merits and demerits, challenges in FSO, and various channel models are discussed. To mitigate the turbulence in FSO the mitigation techniques like relaying, diversity schemes and adopting different modulation techniques used in different channels are discussed and its performance comparison is given.

  2. QUANTUM COMPUTING: Quantum Entangled Bits Step Closer to IT.

    Science.gov (United States)

    Zeilinger, A

    2000-07-21

    In contrast to today's computers, quantum computers and information technologies may in future be able to store and transmit information not only in the state "0" or "1," but also in superpositions of the two; information will then be stored and transmitted in entangled quantum states. Zeilinger discusses recent advances toward using this principle for quantum cryptography and highlights studies into the entanglement (or controlled superposition) of several photons, atoms, or ions.

  3. Coding theory and cryptography the essentials

    CERN Document Server

    Hankerson, DC; Leonard, DA; Phelps, KT; Rodger, CA; Wall, JR; Wall, J R

    2000-01-01

    Containing data on number theory, encryption schemes, and cyclic codes, this highly successful textbook, proven by the authors in a popular two-quarter course, presents coding theory, construction, encoding, and decoding of specific code families in an ""easy-to-use"" manner appropriate for students with only a basic background in mathematics offering revised and updated material on the Berlekamp-Massey decoding algorithm and convolutional codes. Introducing the mathematics as it is needed and providing exercises with solutions, this edition includes an extensive section on cryptography, desig

  4. Cryptography with chaos at the physical level

    International Nuclear Information System (INIS)

    Machado, Romuel F.; Baptista, Murilo S.; Grebogi, C.

    2004-01-01

    In this work, we devise a chaos-based secret key cryptography scheme for digital communication where the encryption is realized at the physical level, that is, the encrypting transformations are applied to the wave signal instead to the symbolic sequence. The encryption process consists of transformations applied to a two-dimensional signal composed of the message carrying signal and an encrypting signal that has to be a chaotic one. The secret key, in this case, is related to the number of times the transformations are applied. Furthermore, we show that due to its chaotic nature, the encrypting signal is able to hide the statistics of the original signal

  5. Comment on "Cheating prevention in visual cryptography".

    Science.gov (United States)

    Chen, Yu-Chi; Horng, Gwoboa; Tsai, Du-Shiau

    2012-07-01

    Visual cryptography (VC), proposed by Naor and Shamir, has numerous applications, including visual authentication and identification, steganography, and image encryption. In 2006, Horng showed that cheating is possible in VC, where some participants can deceive the remaining participants by forged transparencies. Since then, designing cheating-prevention visual secret-sharing (CPVSS) schemes has been studied by many researchers. In this paper, we cryptanalyze the Hu-Tzeng CPVSS scheme and show that it is not cheating immune. We also outline an improvement that helps to overcome the problem.

  6. Random Oracles in a Quantum World

    NARCIS (Netherlands)

    D. Boneh; O. Dagdelen; M. Fischlin; D. Lehmann; C. Schaffner (Christian); M. Zhandry

    2012-01-01

    htmlabstractThe interest in post-quantum cryptography - classical systems that remain secure in the presence of a quantum adversary - has generated elegant proposals for new cryptosystems. Some of these systems are set in the random oracle model and are proven secure relative to adversaries that

  7. Experimental eavesdropping based on optimal quantum cloning

    Czech Academy of Sciences Publication Activity Database

    Bartkiewicz, K.; Lemr, K.; Černoch, Antonín; Soubusta, Jan; Miranowicz, A.

    2013-01-01

    Roč. 110, č. 17 (2013), "173601-1"-"173601-5" ISSN 0031-9007 R&D Projects: GA ČR GAP205/12/0382 Institutional support: RVO:68378271 Keywords : quantum cryptography * qubits * eavesdropping * quantum cloning Subject RIV: BH - Optics, Masers, Lasers Impact factor: 7.728, year: 2013

  8. Finite and profinite quantum systems

    CERN Document Server

    Vourdas, Apostolos

    2017-01-01

    This monograph provides an introduction to finite quantum systems, a field at the interface between quantum information and number theory, with applications in quantum computation and condensed matter physics. The first major part of this monograph studies the so-called `qubits' and `qudits', systems with periodic finite lattice as position space. It also discusses the so-called mutually unbiased bases, which have applications in quantum information and quantum cryptography. Quantum logic and its applications to quantum gates is also studied. The second part studies finite quantum systems, where the position takes values in a Galois field. This combines quantum mechanics with Galois theory. The third part extends the discussion to quantum systems with variables in profinite groups, considering the limit where the dimension of the system becomes very large. It uses the concepts of inverse and direct limit and studies quantum mechanics on p-adic numbers. Applications of the formalism include quantum optics and ...

  9. Extensible router for a quantum key distribution network

    International Nuclear Information System (INIS)

    Zhang Tao; Mo Xiaofan; Han Zhengfu; Guo Guangcan

    2008-01-01

    Building a quantum key distribution network is crucial for practical quantum cryptography. We present a scheme to build a star topology quantum key distribution network based on wavelength division multiplexing which, with current technology, can connect at least a hundred users. With the scheme, a 4-user demonstration network was built up and key exchanges were performed

  10. Quantum information

    International Nuclear Information System (INIS)

    Rodgers, P.

    1998-01-01

    There is more to information than a string of ones and zeroes the ability of ''quantum bits'' to be in two states at the same time could revolutionize information technology. In the mid-1930s two influential but seemingly unrelated papers were published. In 1935 Einstein, Podolsky and Rosen proposed the famous EPR paradox that has come to symbolize the mysteries of quantum mechanics. Two years later, Alan Turing introduced the universal Turing machine in an enigmatically titled paper, On computable numbers, and laid the foundations of the computer industry one of the biggest industries in the world today. Although quantum physics is essential to understand the operation of transistors and other solid-state devices in computers, computation itself has remained a resolutely classical process. Indeed it seems only natural that computation and quantum theory should be kept as far apart as possible surely the uncertainty associated with quantum theory is anathema to the reliability expected from computers? Wrong. In 1985 David Deutsch introduced the universal quantum computer and showed that quantum theory can actually allow computers to do more rather than less. The ability of particles to be in a superposition of more than one quantum state naturally introduces a form of parallelism that can, in principle, perform some traditional computing tasks faster than is possible with classical computers. Moreover, quantum computers are capable of other tasks that are not conceivable with their classical counterparts. Similar breakthroughs in cryptography and communication followed. (author)

  11. Quantum information

    Energy Technology Data Exchange (ETDEWEB)

    Rodgers, P

    1998-03-01

    There is more to information than a string of ones and zeroes the ability of ''quantum bits'' to be in two states at the same time could revolutionize information technology. In the mid-1930s two influential but seemingly unrelated papers were published. In 1935 Einstein, Podolsky and Rosen proposed the famous EPR paradox that has come to symbolize the mysteries of quantum mechanics. Two years later, Alan Turing introduced the universal Turing machine in an enigmatically titled paper, On computable numbers, and laid the foundations of the computer industry one of the biggest industries in the world today. Although quantum physics is essential to understand the operation of transistors and other solid-state devices in computers, computation itself has remained a resolutely classical process. Indeed it seems only natural that computation and quantum theory should be kept as far apart as possible surely the uncertainty associated with quantum theory is anathema to the reliability expected from computers? Wrong. In 1985 David Deutsch introduced the universal quantum computer and showed that quantum theory can actually allow computers to do more rather than less. The ability of particles to be in a superposition of more than one quantum state naturally introduces a form of parallelism that can, in principle, perform some traditional computing tasks faster than is possible with classical computers. Moreover, quantum computers are capable of other tasks that are not conceivable with their classical counterparts. Similar breakthroughs in cryptography and communication followed. (author)

  12. Quantum information

    Energy Technology Data Exchange (ETDEWEB)

    Rodgers, P

    1998-03-01

    There is more to information than a string of ones and zeroes the ability of ''quantum bits'' to be in two states at the same time could revolutionize information technology. In the mid-1930s two influential but seemingly unrelated papers were published. In 1935 Einstein, Podolsky and Rosen proposed the famous EPR paradox that has come to symbolize the mysteries of quantum mechanics. Two years later, Alan Turing introduced the universal Turing machine in an enigmatically titled paper, On computable numbers, and laid the foundations of the computer industry one of the biggest industries in the world today. Although quantum physics is essential to understand the operation of transistors and other solid-state devices in computers, computation itself has remained a resolutely classical process. Indeed it seems only natural that computation and quantum theory should be kept as far apart as possible surely the uncertainty associated with quantum theory is anathema to the reliability expected from computers? Wrong. In 1985 David Deutsch introduced the universal quantum computer and showed that quantum theory can actually allow computers to do more rather than less. The ability of particles to be in a superposition of more than one quantum state naturally introduces a form of parallelism that can, in principle, perform some traditional computing tasks faster than is possible with classical computers. Moreover, quantum computers are capable of other tasks that are not conceivable with their classical counterparts. Similar breakthroughs in cryptography and communication followed. (author)

  13. Information on a Photon: Free-Space Quantum Communication (InPho: FSQC)

    Science.gov (United States)

    2015-10-06

    generate multiple bits per click, e.g., 1 pair in 1024 bins (210)  ~10 bits Get extra 0.5 bpp from BB84 w. polarization. They can constantly check...they detect a photon in to generate multiple bits per click, e.g., 1 pair in 1024 bins (210)  ~10 bits Get extra 0.5 bpp from BB84 w. polarization

  14. Quantum communication with photons

    International Nuclear Information System (INIS)

    Tittel, W.

    2005-01-01

    Full text: The discovery that transmission of information encoded into single quantum systems enables new forms of communication let to the emergence of the domain of quantum communication. During the last ten years, various key experiments based on photons as carrier of the quantum information have been realized. Today, quantum cryptography systems based on faint laser pulses can be purchased commercially, bi-partite entanglement has been distributed over long distances and has been used for quantum key distribution, and quantum purification, teleportation and entanglement swapping have been demonstrated. I will give a general introduction into this fascinating field and will review experimental achievements in the domain of quantum communication with discrete two-level quantum systems (qubits) encoded into photons. (author)

  15. Data transmission with twisted light through a free-space to fiber optical communication link

    International Nuclear Information System (INIS)

    Brüning, Robert; Duparré, Michael; Ndagano, Bienvenu; McLaren, Melanie; Forbes, Andrew; Schröter, Siegmund; Kobelke, Jens

    2016-01-01

    Mode division multiplexing (MDM), where information is transmitted in the spatial modes of light, is mooted as a future technology with which to transmit large bits of information. However, one of the key issues in optical communication lies in connecting free-space to optical fiber networks, otherwise known as the ‘last mile’ problem. This is particularly problematic for MDM as the eigenmodes of free-space and fibers are in general not the same. Here we demonstrate a data transmission scheme across a free-space and fiber link using twisted light in the form of Laguerre–Gaussian (LG) azimuthal modes. As a proof-of-principle we design and implement a custom fiber where the supported LG modes can be grouped into five non-degenerate sets, and successfully transmit a gray-scale image across the composite link using one mode from each group, thereby ensuring minimal crosstalk. (letter)

  16. Application of spinal code for performance improvement in free-space optical communications

    Science.gov (United States)

    Saiki, Naoya; Okamoto, Eiji; Takenaka, Hideki; Toyoshima, Morio

    2017-09-01

    In recent years, the demand for high-capacity communication has grown, and fiber-optic transmission is being used in wired communications to meet this demand. Similarly, free-space optics (FSO), which is an optical wireless communication technology that uses laser light, has attracted much attention and has been considered as a suitable alternative to satisfy this demand in wireless communications. Free-space optical communication uses a hundred THz frequency band and allows for high-speed and radio-regulation free transmission, which may provide a solution for the current shortage of radio frequency bands.

  17. The 'golden' matrices and a new kind of cryptography

    International Nuclear Information System (INIS)

    Stakhov, A.P.

    2007-01-01

    We consider a new class of square matrices called the 'golden' matrices. They are a generalization of the classical Fibonacci Q-matrix for continuous domain. The 'golden' matrices can be used for creation of a new kind of cryptography called the 'golden' cryptography. The method is very fast and simple for technical realization and can be used for cryptographic protection of digital signals (telecommunication and measurement systems)

  18. Securing information display by use of visual cryptography.

    Science.gov (United States)

    Yamamoto, Hirotsugu; Hayasaki, Yoshio; Nishida, Nobuo

    2003-09-01

    We propose a secure display technique based on visual cryptography. The proposed technique ensures the security of visual information. The display employs a decoding mask based on visual cryptography. Without the decoding mask, the displayed information cannot be viewed. The viewing zone is limited by the decoding mask so that only one person can view the information. We have developed a set of encryption codes to maintain the designed viewing zone and have demonstrated a display that provides a limited viewing zone.

  19. A NOVEL ROLLING BASED DNA CRYPTOGRAPHY

    Directory of Open Access Journals (Sweden)

    Rejwana Haque

    2017-05-01

    Full Text Available DNA Cryptography can be defined as a hiding data in terms of DNA Sequence. In this paper we propose a new DNA Encryption Technique where three different types of ordering is use to make binary data into cipher text. The main stages of this encryption technique are: Key Analysis, Data and Key Arrangement, Roll in encoding, Secondary Arrangement and Shifting. Decryption process has six main steps to obtain the original binary data from the encrypted data and key. Decryption steps are: Key Analysis, Shifting, Secondary Arrangement, Key Arrangement, Roll-out decoding, Data Arrangement. Here key size is half of binary data and the key is varies from data to data so key are used as one time pad. In this paper we also discuss about the implementation from sample data and security analysis for this given method.

  20. Introduction to number theory with cryptography

    CERN Document Server

    Kraft, James S

    2013-01-01

    IntroductionDiophantine EquationsModular ArithmeticPrimes and the Distribution of PrimesCryptographyDivisibilityDivisibilityEuclid's Theorem Euclid's Original Proof The Sieve of Eratosthenes The Division Algorithm The Greatest Common Divisor The Euclidean Algorithm Other BasesLinear Diophantine EquationsThe Postage Stamp Problem Fermat and Mersenne Numbers Chapter Highlights Problems Unique FactorizationPreliminary Results The Fundamental Theorem of Arithmetic Euclid and the Fundamental Theorem of ArithmeticChapter Highlights Problems Applications of Unique Factorization A Puzzle Irrationality Proofs The Rational Root Theorem Pythagorean Triples Differences of Squares Prime Factorization of Factorials The Riemann Zeta Function Chapter Highlights Problems CongruencesDefinitions and Examples Modular Exponentiation Divisibility TestsLinear Congruences The Chinese Remainder TheoremFractions mod m Fermat's Theorem Euler's Theorem Wilson's Theorem Queens on a Chessboard Chapter Highlights Problems Cryptographic App...

  1. Experimental investigation of quantum communication protocols in higher dimensions

    International Nuclear Information System (INIS)

    Groeblacher, S.; Stuetz, M.; Vaziri, A.; Jennewein, T.; Zeilinger, A.

    2005-01-01

    Full text: Higher dimensional quantum systems, such as qutrits, offer unique possibilities for quantum communication. In particular, quantum key distribution may be realized with a higher security margin than with qubit systems. We plan to demonstrate quantum cryptography with entangled photonic qutrits based on orbital angular momentum (OAM). Therefore we test various methods of manipulating and transforming OAM states of photons, which is required for the implementation of quantum communication protocols. (author)

  2. Synthesis of Ternary Quantum Logic Circuits by Decomposition

    OpenAIRE

    Khan, Faisal Shah; Perkowski, Marek

    2005-01-01

    Recent research in multi-valued logic for quantum computing has shown practical advantages for scaling up a quantum computer. Multivalued quantum systems have also been used in the framework of quantum cryptography, and the concept of a qudit cluster state has been proposed by generalizing the qubit cluster state. An evolutionary algorithm based synthesizer for ternary quantum circuits has recently been presented, as well as a synthesis method based on matrix factorization.In this paper, a re...

  3. Estimation of Radiation Limit from a Huygens' Box under Non-Free-Space Conditions

    DEFF Research Database (Denmark)

    Franek, Ondrej; Sørensen, Morten; Bonev, Ivan Bonev

    2013-01-01

    The recently studied Huygens' box method has difficulties when radiation of an electronic module is to be determined under non-free-space conditions, i.e. with an enclosure. We propose an estimate on radiation limit under such conditions based only on the Huygens' box data from free...

  4. Performance Analysis of Free-Space Optical Communication Systems With Multiuser Diversity Over Atmospheric Turbulence Channels

    KAUST Repository

    Yang, Liang; Gao, Xiqi; Alouini, Mohamed-Slim

    2014-01-01

    Free-space optical (FSO) communication has become a cost-effective method to provide high data rates. However, the turbulence-induced fading limits its application to short-range applications. To address this, we propose a multiuser diversity (MD

  5. Free Space Optical (FSO) Communications, Towards the Speeds of Wireline Networks

    KAUST Repository

    Alouini, Mohamed-Slim

    2015-01-01

    in the recent past, is not anymore a viable solution to fulfill the demand for more wireless applications and higher data rates. Among the many proposed solutions, optical wireless communication or free-space optical (FSO) systems have gained an increasing

  6. Visible laser and superluminescent diode based free space and underwater communications

    KAUST Repository

    Ooi, Boon S.

    2017-01-30

    We report on our recent progress in high-modulation-efficiency, InGaN-based integrated waveguide modulator-laser diodes (IWM-LDs), high-speed violet and blue emitting superluminescent diodes (SLDs), InGaN-based vertical-cavity surface-emitting lasers (VCSELs), and their applications for gigahertz laser based free-space and underwater wireless optical communications.

  7. Free Space Computation From Stochastic Occupancy Grids Based On Iconic Kalman Filtered Disparity Maps

    DEFF Research Database (Denmark)

    Høilund, Carsten; Moeslund, Thomas B.; Madsen, Claus B.

    2010-01-01

    This paper presents a method for determining the free space in a scene as viewed by a vehicle-mounted camera. Using disparity maps from a stereo camera and known camera motion, the disparity maps are first filtered by an iconic Kalman filter, operating on each pixel individually, thereby reducing...

  8. The metric approximation property and Lipschitz-free spaces over subsets of R-N

    Czech Academy of Sciences Publication Activity Database

    Pernecká, Eva; Smith, R.J.

    2015-01-01

    Roč. 199, November (2015), s. 29-44 ISSN 0021-9045 R&D Projects: GA ČR(CZ) GAP201/11/0345 Institutional support: RVO:67985840 Keywords : Lipschitz-free space * approximation property Subject RIV: BA - General Mathematics Impact factor: 0.921, year: 2015 http://www.sciencedirect.com/science/article/pii/S0021904515000970

  9. Visible laser and superluminescent diode based free space and underwater communications

    KAUST Repository

    Ooi, Boon S.

    2017-01-01

    We report on our recent progress in high-modulation-efficiency, InGaN-based integrated waveguide modulator-laser diodes (IWM-LDs), high-speed violet and blue emitting superluminescent diodes (SLDs), InGaN-based vertical-cavity surface-emitting lasers (VCSELs), and their applications for gigahertz laser based free-space and underwater wireless optical communications.

  10. Quantum

    CERN Document Server

    Al-Khalili, Jim

    2003-01-01

    In this lively look at quantum science, a physicist takes you on an entertaining and enlightening journey through the basics of subatomic physics. Along the way, he examines the paradox of quantum mechanics--beautifully mathematical in theory but confoundingly unpredictable in the real world. Marvel at the Dual Slit experiment as a tiny atom passes through two separate openings at the same time. Ponder the peculiar communication of quantum particles, which can remain in touch no matter how far apart. Join the genius jewel thief as he carries out a quantum measurement on a diamond without ever touching the object in question. Baffle yourself with the bizzareness of quantum tunneling, the equivalent of traveling partway up a hill, only to disappear then reappear traveling down the opposite side. With its clean, colorful layout and conversational tone, this text will hook you into the conundrum that is quantum mechanics.

  11. Applications of quantum entanglement in space

    International Nuclear Information System (INIS)

    Ursin, R.; Aspelmeyer, M.; Jennewein, T.; Zeilinger, A.

    2005-01-01

    Full text: Quantum entanglement is at the heart of quantum physics. At the same time it is the basis for novel quantum communication schemes, such as quantum cryptography over long distances. Bringing quantum entanglement to the space environment will open a new range of fundamental physics experiments, and will provide unique opportunities for quantum communication applications over long distances. We proposed tests of quantum communication in space, whereby an entangled photon Source is placed onboard the ISS, and two entangled photons are transmitted via a simultaneous down link and received at two distant ground stations. Furthermore, performing a series of consecutive single down links with separate ground stations will enable a test of establishing quantum cryptography even on a global scale. This Space-QUEST proposal was submitted within ESA's OA-2004 and was rated as 'outstanding' because of both, a novel and imaginative scientific content and for technological applications of quantum cryptography respectively. We intend to explore the possibilities to send, receive and manipulate single entangled photon pairs using telescopes, reflectors and high-power lasers over a distance of some tens of kilometers up to 100 kilometers experimentally. A distance of approx. 10 kilometer would already correspond to one atmospheric equivalent and would thus imply the feasibility of installing a ground to satellite link. We are already collaborating with European Space Agency ESA, to investigate and outline the accommodation of a quantum communication terminal in existing optical terminals for satellite communication. (author)

  12. Secure communications with low-orbit spacecraft using quantum cryptography

    Science.gov (United States)

    Hughes, Richard J.; Buttler, William T.; Kwiat, Paul G.; Luther, Gabriel G.; Morgan, George L; Nordholt, Jane E.; Peterson, Charles G.; Simmons, Charles M.

    1999-01-01

    Apparatus and method for secure communication between an earth station and spacecraft. A laser outputs single pulses that are split into preceding bright pulses and delayed attenuated pulses, and polarized. A Pockels cell changes the polarization of the polarized delayed attenuated pulses according to a string of random numbers, a first polarization representing a "1," and a second polarization representing a "0." At the receiving station, a beamsplitter randomly directs the preceding bright pulses and the polarized delayed attenuated pulses onto longer and shorter paths, both terminating in a beamsplitter which directs the preceding bright pulses and a first portion of the polarized delayed attenuated pulses to a first detector, and a second portion of the polarized delayed attenuated pulses to a second detector to generate a key for secure communication between the earth station and the spacecraft.

  13. On the Completeness of Quantum Mechanics

    OpenAIRE

    Kupczynski, Marian

    2002-01-01

    Quantum cryptography, quantum computer project, space-time quantization program and recent computer experiments reported by Accardi and his collaborators show the importance and actuality of the discussion of the completeness of quantum mechanics (QM) started by Einstein more than 70 years ago. Many years ago we pointed out that the violation of Bell's inequalities is neither a proof of completeness of QM nor an indication of the violation of Einsteinian causality. We also indicated how and i...

  14. Implementation of diffie-Hellman key exchange on wireless sensor using elliptic curve cryptography

    DEFF Research Database (Denmark)

    Khajuria, Samant; Tange, Henrik

    2009-01-01

    This work describes a low-cost public key cryptography (PKC) based solution for security services such as authentication as required for wireless sensor networks. We have implemented a software approach using elliptic curve cryptography (ECC) over GF (2m) in order to obtain stronger cryptography...

  15. Quantum physics of nature. Theory, experiment and interpretation. in collaboration with 6th European QIPC workshop. General Information, program, abstracts

    International Nuclear Information System (INIS)

    Arndt, M.; Aspelmeyer, M.; Brukner, C.; Weihs, G.; Jennewein, T.; Schmiedmayer, J.; Weinfurter, H.; Zukowski, M.

    2005-01-01

    Quantum information processing and communication is one of the of the key research areas within the European community. Therefore these two events were dedicated to present the advances in this area. Papers dealing with topics such as atom-photon entanglement, matter waves and quantum gases, decoherence, photonic entanglement, solid state quantum physics, cooling and trapping of atoms and molecules, quantum communication, quantum computation, quantum information and quantum cryptography were addressed. (nevyjel)

  16. Quantum memory Quantum memory

    Science.gov (United States)

    Le Gouët, Jean-Louis; Moiseev, Sergey

    2012-06-01

    quest for higher efficiency, better fidelity, broader bandwidth, multimode capacity and longer storage lifetime is pursued in all those approaches, as shown in this special issue. The improvement of quantum memory operation specifically requires in-depth study and control of numerous physical processes leading to atomic decoherence. The present issue reflects the development of rare earth ion doped matrices offering long lifetime superposition states, either as bulk crystals or as optical waveguides. The need for quantum sources and high efficiency detectors at the single photon level is also illustrated. Several papers address the networking of quantum memories either in long-haul cryptography or in the prospect of quantum processing. In this context, much attention has been paid recently to interfacing quantum light with superconducting qubits and with nitrogen-vacancy centers in diamond. Finally, the quantum interfacing of light with matter raises questions on entanglement. The last two papers are devoted to the generation of entanglement by dissipative processes. It is shown that long lifetime entanglement may be built in this way. We hope this special issue will help readers to become familiar with the exciting field of ensemble-based quantum memories and will stimulate them to bring deeper insights and new ideas to this area.

  17. QC-LDPC code-based cryptography

    CERN Document Server

    Baldi, Marco

    2014-01-01

    This book describes the fundamentals of cryptographic primitives based on quasi-cyclic low-density parity-check (QC-LDPC) codes, with a special focus on the use of these codes in public-key cryptosystems derived from the McEliece and Niederreiter schemes. In the first part of the book, the main characteristics of QC-LDPC codes are reviewed, and several techniques for their design are presented, while tools for assessing the error correction performance of these codes are also described. Some families of QC-LDPC codes that are best suited for use in cryptography are also presented. The second part of the book focuses on the McEliece and Niederreiter cryptosystems, both in their original forms and in some subsequent variants. The applicability of QC-LDPC codes in these frameworks is investigated by means of theoretical analyses and numerical tools, in order to assess their benefits and drawbacks in terms of system efficiency and security. Several examples of QC-LDPC code-based public key cryptosystems are prese...

  18. Handbook of elliptic and hyperelliptic curve cryptography

    CERN Document Server

    Cohen, Henri; Avanzi, Roberto; Doche, Christophe; Lange, Tanja; Nguyen, Kim; Vercauteren, Frederik

    2005-01-01

    … very comprehensive coverage of this vast subject area … a useful and essential treatise for anyone involved in elliptic curve algorithms … this book offers the opportunity to grasp the ECC technology with a diversified and comprehensive perspective. … This book will remain on my shelf for a long time and will land on my desk on many occasions, if only because the coverage of the issues common to factoring and discrete log cryptosystems is excellent.-IACR Book Reviews, June 2011… the book is designed for people who are working in the area and want to learn more about a specific issue. The chapters are written to be relatively independent so that readers can focus on the part of interest for them. Such readers will be grateful for the excellent index and extensive bibliography. … the handbook covers a wide range of topics and will be a valuable reference for researchers in curve-based cryptography. -Steven D. Galbraith, Mathematical Reviews, Issue 2007f.

  19. Experimental verification of free-space singular boundary conditions in an invisibility cloak

    International Nuclear Information System (INIS)

    Wu, Qiannan; Gao, Fei; Song, Zhengyong; Lin, Xiao; Zhang, Youming; Zhang, Baile; Chen, Huanyang

    2016-01-01

    A major issue in invisibility cloaking, which caused intense mathematical discussions in the past few years but still remains physically elusive, is the plausible singular boundary conditions associated with the singular metamaterials at the inner boundary of an invisibility cloak. The perfect cloaking phenomenon, as originally proposed by Pendry et al for electromagnetic waves, cannot be treated as physical before a realistic inner boundary of a cloak is demonstrated. Although a recent demonstration has been done in a waveguide environment, the exotic singular boundary conditions should apply to a general environment as in free space. Here we fabricate a metamaterial surface that exhibits the singular boundary conditions and demonstrate its performance in free space. Particularly, the phase information of waves reflected from this metamaterial surface is explicitly measured, confirming the singular responses of boundary conditions for an invisibility cloak. (paper)

  20. Experimental verification of free-space singular boundary conditions in an invisibility cloak

    Science.gov (United States)

    Wu, Qiannan; Gao, Fei; Song, Zhengyong; Lin, Xiao; Zhang, Youming; Chen, Huanyang; Zhang, Baile

    2016-04-01

    A major issue in invisibility cloaking, which caused intense mathematical discussions in the past few years but still remains physically elusive, is the plausible singular boundary conditions associated with the singular metamaterials at the inner boundary of an invisibility cloak. The perfect cloaking phenomenon, as originally proposed by Pendry et al for electromagnetic waves, cannot be treated as physical before a realistic inner boundary of a cloak is demonstrated. Although a recent demonstration has been done in a waveguide environment, the exotic singular boundary conditions should apply to a general environment as in free space. Here we fabricate a metamaterial surface that exhibits the singular boundary conditions and demonstrate its performance in free space. Particularly, the phase information of waves reflected from this metamaterial surface is explicitly measured, confirming the singular responses of boundary conditions for an invisibility cloak.

  1. Composite optical vortices in noncollinear Laguerre–Gaussian beams and their propagation in free space

    International Nuclear Information System (INIS)

    Chen Ke; Liu Pusheng; Lü Baida

    2008-01-01

    Taking two Laguerre—Gaussian beams with topological charge l = ± 1 as an example, this paper studies the composite optical vortices formed by two noncollinear Laguerre—Gaussian beams with different phases, amplitudes, waist widths, off-axis distances, and their propagation in free space. It is shown by detailed numerical illustrative examples that the number and location of composite vortices at the waist plane are variable by varying the relative phase β, amplitude ratio η, waist width ratio ζ, or off-axis distance ratio μ. The net topological charge l net is not always equal to the sum l sum of charges of the two component beams. The motion, creation and annihilation of composite vortices take place in the free-space propagation, and the net charge during the propagation remains unchanged and equals to the net charge at the waist plane

  2. Optical power allocation for adaptive transmissions in wavelength-division multiplexing free space optical networks

    Directory of Open Access Journals (Sweden)

    Hui Zhou

    2015-08-01

    Full Text Available Attracting increasing attention in recent years, the Free Space Optics (FSO technology has been recognized as a cost-effective wireless access technology for multi-Gigabit rate wireless networks. Radio on Free Space Optics (RoFSO provides a new approach to support various bandwidth-intensive wireless services in an optical wireless link. In an RoFSO system using wavelength-division multiplexing (WDM, it is possible to concurrently transmit multiple data streams consisting of various wireless services at very high rate. In this paper, we investigate the problem of optical power allocation under power budget and eye safety constraints for adaptive WDM transmission in RoFSO networks. We develop power allocation schemes for adaptive WDM transmissions to combat the effect of weather turbulence on RoFSO links. Simulation results show that WDM RoFSO can support high data rates even over long distance or under bad weather conditions with an adequate system design.

  3. The Potential Impact of Quantum Computers on Society

    OpenAIRE

    de Wolf, Ronald

    2017-01-01

    This paper considers the potential impact that the nascent technology of quantum computing may have on society. It focuses on three areas: cryptography, optimization, and simulation of quantum systems. We will also discuss some ethical aspects of these developments, and ways to mitigate the risks.

  4. The potential impact of quantum computers on society

    NARCIS (Netherlands)

    2017-01-01

    textabstractThis paper considers the potential impact that the nascent technology of quantum computing may have on society. It focuses on three areas: cryptography, optimization, and simulation of quantum systems. We will also discuss some ethical aspects of these developments, and ways to mitigate

  5. Efficient amplification of photonic qubits by optimal quantum cloning

    Czech Academy of Sciences Publication Activity Database

    Bartkiewicz, K.; Černoch, A.; Lemr, K.; Soubusta, Jan; Stobińska, M.

    2014-01-01

    Roč. 89, č. 6 (2014), "062322-1"-"062322-10" ISSN 1050-2947 Institutional support: RVO:68378271 Keywords : optimal quantum cloning * cryptography * qubit * phase-independent quantum amplifier Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.808, year: 2014

  6. Multi-Element Free-Space Optical (FSO) Modules for Mobile-Opportunistic Networking

    Science.gov (United States)

    2016-11-14

    due to license-free spectrum, containment of beams, inherent security, energy efficient communications, and high transmission rates. We leveraged the... wireless spectrum bands in both military and civilian settings. Recent research has shown that free- space-optical (FSO), a.k.a. optical wireless ...communications is a promising complementary approach to address the exploding mobile wireless traffic demand. The major impediment for using FSO in a

  7. The Generation Mechanism of Airy—Bessel Wave Packets in Free Space

    International Nuclear Information System (INIS)

    Ren Zhi-Jun; Ying Chao-Fu; Fan Chang-Jiang; Wu Qiong

    2012-01-01

    Localized optical Airy—Bessel configuration wave packets were first generated on the basis of a grating-telescope combination [Nat. Photon. 4(2010) 103]. By studying the spatially induced group velocity dispersion effect of ultrashort pulsed Bessel beams during propagation, we find the universal physical foundation of generating Airy—Bessel wave packets (ABWs) in free space. The research results are expected to open up more common channels for generating stable linear localized ABWs

  8. Obstacle evasion in free-space optical communications utilizing Airy beams

    Science.gov (United States)

    Zhu, Guoxuan; Wen, Yuanhui; Wu, Xiong; Chen, Yujie; Liu, Jie; Yu, Siyuan

    2018-03-01

    A high speed free-space optical communication system capable of self-bending signal transmission around line-of-sight obstacles is proposed and demonstrated. Airy beams are generated and controlled to achieve different propagating trajectories, and the signal transmission characteristics of these beams around the obstacle are investigated. Our results confirm that, by optimising their ballistic trajectories, Airy beams are able to bypass obstacles with more signal energy and thus improve the communication performance compared with normal Gaussian beams.

  9. Estimation of optical attenuation in reduced visibility conditions in different environments across free space optics link

    Czech Academy of Sciences Publication Activity Database

    Dev, K.; Nebuloni, R.; Capsoni, C.; Fišer, Ondřej; Brázda, V.

    2017-01-01

    Roč. 11, č. 12 (2017), s. 1708-1713 ISSN 1751-8725 Institutional support: RVO:68378289 Keywords : light attenuation * optical sensors * free-space optical communication Subject RIV: DG - Athmosphere Sciences, Meteorology OBOR OECD: Meteorology and atmospheric sciences Impact factor: 1.187, year: 2016 http://digital-library.theiet.org/content/journals/10.1049/iet-map.2016.0872

  10. Role of transverse-momentum currents in the optical Magnus effect in free space

    OpenAIRE

    Luo, Hailu; Wen, Shuangchun; Shu, Weixing; Fan, Dianyuan

    2010-01-01

    We establish a general vector field model to describe the role of transverse-momentum currents in the optical Magnus effect in free space. As an analogy of the mechanical Magnus effect, the circularly polarized wave packet in our model acts as the rotating ball, and its rotation direction depends on the polarization state. Based on this model, we demonstrate the existence of an optical polarization-dependent Magnus effect which is significantly different from the conventional optical Magnus e...

  11. Free-Space Squeezing Assists Perfectly Matched Layers in Simulations on a Tight Domain

    DEFF Research Database (Denmark)

    Shyroki, Dzmitry; Ivinskaya, Aliaksandra; Lavrinenko, Andrei

    2010-01-01

    outside the object, as in simulations of eigenmodes or scattering at a wavelength comparable to or larger than the object itself. Here, we show how, in addition to applying the perfectly matched layers (PMLs), outer free space can be squeezed to avoid cutting the evanescent field tails by the PMLs...... or computational domain borders. Adding the squeeze-transform layers to the standard PMLs requires no changes to the finite-difference algorithms....

  12. Complex Permittivity Measurements of Textiles and Leather in a Free Space: An Angular-Invariant Approach

    OpenAIRE

    Kapilevich, B.; Litvak, B.; Anisimov, M.; Hardon, D.; Pinhasi, Y.

    2012-01-01

    The paper describes the complex permittivity measurements of textiles and leathers in a free space at 330 GHz. The destructive role of the Rayleigh scattering effect is considered and the angular-invariant limit for an incidence angle has been found out experimentally within 25–30 degrees. If incidence angle exceeds this critical parameter, the uncertainty caused by the Rayleigh scattering is drastically increased preventing accurate measurements of the real and imaginary parts of a bulky mat...

  13. Gaps of free-space optics beams with the Beer-Lambert law.

    Science.gov (United States)

    Lacaze, Bernard

    2009-05-10

    Lasers used in free-space optics propagate a beam within a truncated cone. Because of this shape, the intensity cannot follow the Beer-Lambert law. In the case of a homogeneous atmosphere, we calculate the gap from the cylinder case. We will see that the gap exists but is generally very weak and, therefore, that the use of the Beer-Lambert law is a justified approximation.

  14. High-dimensional free-space optical communications based on orbital angular momentum coding

    Science.gov (United States)

    Zou, Li; Gu, Xiaofan; Wang, Le

    2018-03-01

    In this paper, we propose a high-dimensional free-space optical communication scheme using orbital angular momentum (OAM) coding. In the scheme, the transmitter encodes N-bits information by using a spatial light modulator to convert a Gaussian beam to a superposition mode of N OAM modes and a Gaussian mode; The receiver decodes the information through an OAM mode analyser which consists of a MZ interferometer with a rotating Dove prism, a photoelectric detector and a computer carrying out the fast Fourier transform. The scheme could realize a high-dimensional free-space optical communication, and decodes the information much fast and accurately. We have verified the feasibility of the scheme by exploiting 8 (4) OAM modes and a Gaussian mode to implement a 256-ary (16-ary) coding free-space optical communication to transmit a 256-gray-scale (16-gray-scale) picture. The results show that a zero bit error rate performance has been achieved.

  15. Integrated Quantum Optics: Experiments towards integrated quantum-light sources and quantum-enhanced sensing

    DEFF Research Database (Denmark)

    Hoff, Ulrich Busk

    The work presented in this thesis is focused on experimental application and generation of continuous variable quantum correlated states of light in integrated dielectric structures. Squeezed states are among the most exploited continuous variable optical states for free-space quantum-enhanced se...... is presented and an optimized device design is proposed. The devices have been fabricated and tested optically and preliminary interrogations of the output quantum noise have been performed....

  16. Generalized logistic map and its application in chaos based cryptography

    Science.gov (United States)

    Lawnik, M.

    2017-12-01

    The logistic map is commonly used in, for example, chaos based cryptography. However, its properties do not render a safe construction of encryption algorithms. Thus, the scope of the paper is a proposal of generalization of the logistic map by means of a wellrecognized family of chaotic maps. In the next step, an analysis of Lyapunov exponent and the distribution of the iterative variable are studied. The obtained results confirm that the analyzed model can safely and effectively replace a classic logistic map for applications involving chaotic cryptography.

  17. Evolution of orbital angular momentum entangled bi-photon, propagating through a turbulent atmosphere

    CSIR Research Space (South Africa)

    Roux, FS

    2011-01-01

    Full Text Available Orbital angular momentum (OAM) entangled bi-photons are a resource for the higher dimensional implementation of quantum cryptography, which allows secure communication over various channels. In the case where free-space is used as communication...

  18. The DARPA quantum network

    International Nuclear Information System (INIS)

    Elliot, B.

    2005-01-01

    Full text: The DARPA quantum network is now in initial operational, with six nodes performing quantum cryptography 24x7 across the Boston metro area between our campuses at Harvard University, Boston University, and BBN Technologies. In this talk, we present our recent activities, including the deployment of this network, building our Mark 1 Entangled QKD system, porting BBN QKD protocol software to NIST and Qinetiq freespace systems, performing initial design of a superconducting single photon detector with U. Rochester and NIST Boulder, and implementing a novel Low-Density Parity Check (LDPC) protocol for QKD. (author)

  19. Adaptive Hardware Cryptography Engine Based on FPGA

    International Nuclear Information System (INIS)

    Afify, M.A.A.

    2011-01-01

    In the last two decades, with spread of the real time applications over public networks or communications the need for information security become more important but with very high speed for data processing, to keep up with the real time applications requirements, that is the reason for using FPGA as an implementation platform for the proposed cryptography engine. Hence in this thesis a new S-Box design has been demonstrated and implemented, there is a comparison for the simulation results for proposed S-Box simulation results with respect to different designs for S-Box in DES, Two fish and Rijndael algorithms and another comparison among proposed S-Box with different sizes. The proposed S-Box implemented with 32-bits Input data lines and compared with different designs in the encryption algorithms with the same input lines, the proposed S-Box gives implementation results for the maximum frequency 120 MHz but the DES S-Box gives 34 MHz and Rijndael gives 71 MHz, on the other hand the proposed design gives the best implementation area, hence it gives 50 Configurable logic Block CLB but DES gives 88 CLB. The proposed S-Box implemented in different sizes 64-bits, 128-bits, and 256-bits for input data lines. The implementation carried out by using UniDAq PCI card with FPGA Chip XCV 800, synthesizing carried out for all designs by using Leonardo spectrum and simulation carried out by using model sim simulator program form the FPGA advantage package. Finally the results evaluation and verifications carried out using the UniDAq FPGA PCI card with chip XCV 800. Different cases study have been implemented, data encryption, images encryption, voice encryption, and video encryption. A prototype for Remote Monitoring Control System has been implemented. Finally the proposed design for S-Box has a significant achievement in maximum frequency, implementation area, and encryption strength.

  20. Introduction to public-key cryptography (Chapter 1)

    NARCIS (Netherlands)

    Avanzi, R.; Lange, T.; Cohen, H.; Frey, G.

    2006-01-01

    In this chapter we introduce the basic building blocks for cryptography based on the discrete logarithm problem that will constitute the main motivation for considering the groups studied in this book. We also briefly introduce the RSA cryptosystem as for use in practice it is still an important

  1. The mathematics of ciphers number theory and RSA cryptography

    CERN Document Server

    Coutinho, S C

    1999-01-01

    This book is an introduction to the algorithmic aspects of number theory and its applications to cryptography, with special emphasis on the RSA cryptosys-tem. It covers many of the familiar topics of elementary number theory, all with an algorithmic twist. The text also includes many interesting historical notes.

  2. APE: Authenticated Permutation-Based Encryption for Lightweight Cryptography

    DEFF Research Database (Denmark)

    Andreeva, Elena; Bilgin, Begül; Bogdanov, Andrey

    2015-01-01

    The domain of lightweight cryptography focuses on cryptographic algorithms for extremely constrained devices. It is very costly to avoid nonce reuse in such environments, because this requires either a hardware source of randomness, or non-volatile memory to store a counter. At the same time, a lot...

  3. A "proof-reading" of Some Issues in Cryptography

    DEFF Research Database (Denmark)

    Damgård, Ivan Bjerre

    2007-01-01

    In this paper, we identify some issues in the interplay between practice and theory in cryptography, issues that have repeatedly appeared in different incarnations over the years. These issues are related to fundamental concepts in the eld, e.g., to what extent we can prove that a system is secure...

  4. Enhancing Undergraduate Mathematics Curriculum via Coding Theory and Cryptography

    Science.gov (United States)

    Aydin, Nuh

    2009-01-01

    The theory of error-correcting codes and cryptography are two relatively recent applications of mathematics to information and communication systems. The mathematical tools used in these fields generally come from algebra, elementary number theory, and combinatorics, including concepts from computational complexity. It is possible to introduce the…

  5. Steganography and Cryptography Inspired Enhancement of Introductory Programming Courses

    Science.gov (United States)

    Kortsarts, Yana; Kempner, Yulia

    2015-01-01

    Steganography is the art and science of concealing communication. The goal of steganography is to hide the very existence of information exchange by embedding messages into unsuspicious digital media covers. Cryptography, or secret writing, is the study of the methods of encryption, decryption and their use in communications protocols.…

  6. Fast elliptic-curve cryptography on the Cell Broadband Engine

    NARCIS (Netherlands)

    Costigan, N.; Schwabe, P.; Preneel, B.

    2009-01-01

    This paper is the first to investigate the power of the Cell Broadband Engine for state-of-the-art public-key cryptography. We present a high-speed implementation of elliptic-curve Diffie-Hellman (ECDH) key exchange for this processor, which needs 697080 cycles on one Synergistic Processor Unit for

  7. Cryptography- An ideal solution to privacy, data integrity and non ...

    African Journals Online (AJOL)

    Encryption, hashing and digital signatures are the three primitives of Cryptography and these have been treated in depth and their performances on text data and image data have been studied The most secure algorithms so far in use have been introduced and the respective performance of each primitive 's algorithm on ...

  8. Introduction to Cryptography and the Bitcoin Protocol (1/2)

    CERN Multimedia

    CERN. Geneva

    2014-01-01

    The Bitcoin protocol not only supports an electronic currency, but also has the possibility for being (mis)used in other ways. Topics will include the basic operation of how Bitcoin operates including motivations and also such things as block chaining, bitcoin mining, and how financial transactions operate. A knowledge of the topics covered in the Basic Cryptography lecture will be assumed.

  9. Introduction to Cryptography and the Bitcoin Protocol (2/2)

    CERN Multimedia

    CERN. Geneva

    2014-01-01

    The Bitcoin protocol not only supports an electronic currency, but also has the possibility for being (mis)used in other ways. Topics will include the basic operation of how Bitcoin operates including motivations and also such things as block chaining, bitcoin mining, and how financial transactions operate. A knowledge of the topics covered in the Basic Cryptography lecture will be assumed.

  10. Dosimetric significance of cosmic radiation in the altitude of SST and in free space

    Energy Technology Data Exchange (ETDEWEB)

    Allkofer, O C [Kiel Univ. (Germany, F.R.). Inst. fuer Reine und Angewandte Kernphysik

    1977-01-01

    The integral cosmic-ray flux, and hence the dose rate, increases with altitude. At the cruising altitude of the subsonic jets, about 10 km, the dose rate is already about a factor 70 higher than at sea level. At the higher altitudes of SST the situation is different because the composition of the galactic component differs from that at the subsonic level, the solar flares are more efficient, and a small number of heavy nuclei are still present. In free space an additional radiation hazard appears when the radiation belts have to be crossed.

  11. Electro-Optical Sensing Apparatus and Method for Characterizing Free-Space Electromagnetic Radiation

    Science.gov (United States)

    Zhang, Xi-Cheng; Libelo, Louis Francis; Wu, Qi

    1999-09-14

    Apparatus and methods for characterizing free-space electromagnetic energy, and in particular, apparatus/method suitable for real-time two-dimensional far-infrared imaging applications are presented. The sensing technique is based on a non-linear coupling between a low-frequency electric field and a laser beam in an electro-optic crystal. In addition to a practical counter-propagating sensing technique, a co-linear approach is described which provides longer radiated field--optical beam interaction length, thereby making imaging applications practical.

  12. Characterization of dual-polarization LTE radio over a free-space optical turbulence channel.

    Science.gov (United States)

    Bohata, J; Zvanovec, S; Korinek, T; Mansour Abadi, M; Ghassemlooy, Z

    2015-08-10

    A dual polarization (DP) radio over a free-space optical (FSO) communication link using a long-term evolution (LTE) radio signal is proposed and analyzed under different turbulence channel conditions. Radio signal transmission over the DP FSO channel is experimentally verified by means of error vector magnitude (EVM) statistics. We demonstrate that such a system, employing a 64 quadrature amplitude modulation at the frequency bands of 800 MHz and 2.6 GHz, evinces reliability with LTE signal over the FSO channel is a potential solution for last-mile access or backbone networks, when using multiple-input multiple-output based DP signals.

  13. Overlap relation between free-space Laguerre Gaussian modes and step-index fiber modes

    CSIR Research Space (South Africa)

    Bruning, R

    2015-09-01

    Full Text Available to control the optical proper- ties of the emerging beam or the excited field distributions at the fiber input. The simplest connection is given by fibers with an parabolic refractive index profile, typical of graded-index fibers, whose modes can be described..., in general free space modes are not suitable to excite selective pure fiber modes and additional beam shaping techniques are required, such as the use of computer generated holograms [5]. The main disadvan- tages of such beam shaping techniques are the low...

  14. Experimental verification of three-dimensional plasmonic cloaking in free-space

    International Nuclear Information System (INIS)

    Rainwater, D; Kerkhoff, A; Melin, K; Soric, J C; Moreno, G; Alù, A

    2012-01-01

    We report the experimental verification of metamaterial cloaking for a 3D object in free space. We apply the plasmonic cloaking technique, based on scattering cancellation, to suppress microwave scattering from a finite-length dielectric cylinder. We verify that scattering suppression is obtained all around the object in the near- and far-field and for different incidence angles, validating our measurements with analytical results and full-wave simulations. Our near-field and far-field measurements confirm that realistic and robust plasmonic metamaterial cloaks may be realized for elongated 3D objects with moderate transverse cross-section at microwave frequencies. (paper)

  15. Wigner functions for nonparaxial, arbitrarily polarized electromagnetic wave fields in free space.

    Science.gov (United States)

    Alonso, Miguel A

    2004-11-01

    New representations are defined for describing electromagnetic wave fields in free space exactly in terms of rays for any wavelength, level of coherence or polarization, and numerical aperture, as long as there are no evanescent components. These representations correspond to tensors assigned to each ray such that the electric and magnetic energy densities, the Poynting vector, and the polarization properties of the field correspond to simple integrals involving these tensors for the rays that go through the specified point. For partially coherent fields, the ray-based approach provided by the new representations can reduce dramatically the computation times for the physical properties mentioned earlier.

  16. On the performance of free-space optical communication systems with multiuser diversity

    KAUST Repository

    Yang, Liang

    2014-09-01

    Free space optical (FSO) communication has become a cost-effective method to provide high data rates. However, the turbulence-induced fading limits its application to short range applications. To address this, we propose a multiuser diversity (MD) FSO scheme in which the Nth best user is selected and the channel fluctuations can be effectively exploited to produce a selection diversity gain. More specifically, we first present the statistics analysis for the considered system over weak atmospheric turbulence channels. Based on these statistics, the outage probability, bit-error rate performance, and coverage are analyzed.

  17. Experimental demonstration of free-space optical vortex transmutation with polygonal lenses.

    Science.gov (United States)

    Gao, Nan; Xie, Changqing

    2012-08-01

    Vortex transmutation was predicted to take place when vortices interact with systems possessing discrete rotational symmetries of finite order [Phys. Rev. Lett.95, 123901 (2005)]. Here we report what is believed to be the first experimental demonstration of vortex transmutation. We show that in free space, by simply inserting polygonal lenses into the optical path, the central vorticity of a coaxially incident optical vortex can be changed following the modular transmutation rule. We generate the wavefront at the exit face of the lenses with computer generated holograms and measure the output vorticity using the interference patterns at the focal plane. The results agree well with theoretical predictions.

  18. Versatile element for free-space dividing and redirecting neutral-atom clouds

    International Nuclear Information System (INIS)

    Arakelyan, I. V.; Chattrapiban, N.; Mitra, S.; Hill, W. T. III

    2007-01-01

    We introduce a tunnel lock that can be exploited to divide, delay, and alter the direction of traveling clouds of cold atoms. This versatile free-space element is implemented by crossing two atom tunnels formed by low-intensity, blue-detuned dark-hollow (Bessel mode) laser beams. We show that clouds of cold Rb atoms initially moving within one tunnel can be transferred to the other without heating by gating the intensities of the two tunnels--a tunnel lock--with an efficiency limited by the overlap volume. The element also can be used to divide a single cloud into smaller clouds, each having a distinct momentum

  19. Modeling of Fog and Smoke Attenuation in Free Space Optical Communications Link Under Controlled Laboratory Conditions

    Czech Academy of Sciences Publication Activity Database

    Ijaz, M.; Ghassemlooy, Z.; Pešek, J.; Fišer, Ondřej; Le Minh, H.; Bentley, E.

    2013-01-01

    Roč. 31, č. 11 (2013), s. 1720-1726 ISSN 0733-8724 R&D Projects: GA ČR(CZ) GAP102/11/1376 Institutional support: RVO:68378289 Keywords : Fog attenuation * free space optics * smoke attenuation * visibility Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 2.862, year: 2013 http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6497447&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6497447

  20. Filamentation of a surface plasma wave over a semiconductor-free space interface

    Science.gov (United States)

    Kumar, Gagan; Tripathi, V. K.

    2007-12-01

    A large amplitude surface plasma wave (SPW), propagating over a semiconductor-free space interface, is susceptible to filamentation instability. A small perturbation in the amplitude of the SPW across the direction of propagation exerts a ponderomotive force on free electrons and holes, causing spatial modulation in free carrier density and hence the effective permittivity ɛeff of the semiconductor. The regions with higher ɛeff attract more power from the nieghborhood, leading to the growth of the perturbation. The growth rate increases with the intensity of the surface wave. It decreases with the frequency of the SPW.

  1. Design and simulation of a planar micro-optic free-space receiver

    Science.gov (United States)

    Nadler, Brett R.; Hallas, Justin M.; Karp, Jason H.; Ford, Joseph E.

    2017-11-01

    We propose a compact directional optical receiver for free-space communications, where a microlens array and micro-optic structures selectively couple light from a narrow incidence angle into a thin slab waveguide and then to an edge-mounted detector. A small lateral translation of the lenslet array controls the coupled input angle, enabling the receiver to select the transmitter source direction. We present the optical design and simulation of a 10mm x 10mm aperture receiver using a 30μm thick silicon waveguide able to couple up to 2.5Gbps modulated input to a 10mm x 30μm wide detector.

  2. Entangled photons and quantum communication

    Energy Technology Data Exchange (ETDEWEB)

    Yuan Zhensheng, E-mail: yuanzs@ustc.edu.c [Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Physikalisches Institut, Universitaet Heidelberg, Philosophenweg 12, 69120 Heidelberg (Germany); Bao Xiaohui [Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Physikalisches Institut, Universitaet Heidelberg, Philosophenweg 12, 69120 Heidelberg (Germany); Lu Chaoyang; Zhang Jun; Peng Chengzhi [Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Pan Jianwei, E-mail: pan@ustc.edu.c [Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Physikalisches Institut, Universitaet Heidelberg, Philosophenweg 12, 69120 Heidelberg (Germany)

    2010-12-15

    This article reviews the progress of quantum communication that utilizes photonic entanglement. We start with a survey of various methods for generating entangled photons, followed by an introduction of the theoretical principles and the experimental implementations of quantum key distribution. We then move on to a discussion of more involved quantum communication protocols including quantum dense coding, teleportation and quantum communication complexity. After that, we review the progress in free-space quantum communication, decoherence-free subspace, and quantum repeater protocols which are essential ingredients for long-distance quantum communication. Practical realizations of quantum repeaters, which require an interface between photons and quantum memories, are discussed briefly. Finally, we draw concluding remarks considering the technical challenges, and put forward an outlook on further developments of this field.

  3. Entangled photons and quantum communication

    International Nuclear Information System (INIS)

    Yuan Zhensheng; Bao Xiaohui; Lu Chaoyang; Zhang Jun; Peng Chengzhi; Pan Jianwei

    2010-01-01

    This article reviews the progress of quantum communication that utilizes photonic entanglement. We start with a survey of various methods for generating entangled photons, followed by an introduction of the theoretical principles and the experimental implementations of quantum key distribution. We then move on to a discussion of more involved quantum communication protocols including quantum dense coding, teleportation and quantum communication complexity. After that, we review the progress in free-space quantum communication, decoherence-free subspace, and quantum repeater protocols which are essential ingredients for long-distance quantum communication. Practical realizations of quantum repeaters, which require an interface between photons and quantum memories, are discussed briefly. Finally, we draw concluding remarks considering the technical challenges, and put forward an outlook on further developments of this field.

  4. Threshold-Based Multiple Optical Signal Selection Scheme for Free-Space Optical Wavelength Division Multiplexing Systems

    KAUST Repository

    Nam, Sung Sik; Alouini, Mohamed-Slim; Zhang, Lin; Ko, Young-Chai

    2017-01-01

    We propose a threshold-based multiple optical signal selection scheme (TMOS) for free-space optical wavelength division multiplexing systems. With this scheme, we can obtain higher spectral efficiency while reducing the possible complexity

  5. Parallel Device-Independent Quantum Key Distribution

    OpenAIRE

    Jain, Rahul; Miller, Carl A.; Shi, Yaoyun

    2017-01-01

    A prominent application of quantum cryptography is the distribution of cryptographic keys with unconditional security. Recently, such security was extended by Vazirani and Vidick (Physical Review Letters, 113, 140501, 2014) to the device-independent (DI) scenario, where the users do not need to trust the integrity of the underlying quantum devices. The protocols analyzed by them and by subsequent authors all require a sequential execution of N multiplayer games, where N is the security parame...

  6. Energy efficient rateless codes for high speed data transfer over free space optical channels

    Science.gov (United States)

    Prakash, Geetha; Kulkarni, Muralidhar; Acharya, U. S.

    2015-03-01

    Terrestrial Free Space Optical (FSO) links transmit information by using the atmosphere (free space) as a medium. In this paper, we have investigated the use of Luby Transform (LT) codes as a means to mitigate the effects of data corruption induced by imperfect channel which usually takes the form of lost or corrupted packets. LT codes, which are a class of Fountain codes, can be used independent of the channel rate and as many code words as required can be generated to recover all the message bits irrespective of the channel performance. Achieving error free high data rates with limited energy resources is possible with FSO systems if error correction codes with minimal overheads on the power can be used. We also employ a combination of Binary Phase Shift Keying (BPSK) with provision for modification of threshold and optimized LT codes with belief propagation for decoding. These techniques provide additional protection even under strong turbulence regimes. Automatic Repeat Request (ARQ) is another method of improving link reliability. Performance of ARQ is limited by the number of retransmissions and the corresponding time delay. We prove through theoretical computations and simulations that LT codes consume less energy per bit. We validate the feasibility of using energy efficient LT codes over ARQ for FSO links to be used in optical wireless sensor networks within the eye safety limits.

  7. Corrections to air kerma rate measurements of 125I brachytherapy sources to free space conditions

    International Nuclear Information System (INIS)

    Shipley, D.R.; Duane, S.

    1994-05-01

    Air kerma rate measurements have been made between 40 cm and 100 cm from one of a set of 125 I reference sources within the facilities of Amersham International plc. Monte Carlo techniques have been used to calculate the air kerma rate components over the same range of distances from this source. After comparing the calculated data with measurements, the compliance of the data with the inverse square law was investigated, and corrections were derived to obtain the air kerma rate at 1 m in free space from each source. Simulations of the experimental setup with an isotropic monoenergetic point source close to the effective energy of 125 I were found to reproduce the air kerma rate measurements reasonably accurately, and indicated that the contribution due to scattered photons was significant. The overall correction (which is defined as the product of individual corrections for chamber size effect, air attenuation and radiation scatter) required to the inverse square law to obtain the air kerma rate at 1 m in free space was found to be 0.981, 0.984 and 0.980, respectively, for air kerma rate measurements at 40 cm, 60 cm and 100 cm from the 125 I reference source. The total uncertainty in these corrections was estimated to be 0.88% at the 1σ level. (author)

  8. Role of transverse-momentum currents in the optical Magnus effect in free space

    International Nuclear Information System (INIS)

    Luo Hailu; Wen Shuangchun; Shu Weixing; Fan Dianyuan

    2010-01-01

    We establish a general vector field model to describe the role of transverse-momentum currents in the optical Magnus effect in free space. As an analogy of the mechanical Magnus effect, the circularly polarized wave packet in our model acts as the rotating ball, and its rotation direction depends on the polarization state. Based on this model, we demonstrate the existence of an optical polarization-dependent Magnus effect which is significantly different from the conventional optical Magnus effect in that light-matter interaction is not required. Further, we reveal the relation between transverse-momentum currents and the optical Magnus effect, and find that such a polarization-dependent rotation is unavoidable when the wave packet possesses transverse-momentum currents. The physics underlying this intriguing effect is the combined contributions of transverse spin and orbital currents. We predict that this effect may be observed experimentally even in the propagation direction. These findings provide further evidence for the optical Magnus effect in free space and can be extrapolated to other physical systems.

  9. Performance analysis of stationary Hadamard matrix diffusers in free-space optical communication links

    Science.gov (United States)

    Burrell, Derek J.; Middlebrook, Christopher T.

    2017-08-01

    Wireless communication systems that employ free-space optical links in place of radio/microwave technologies carry substantial benefits in terms of data throughput, network security and design efficiency. Along with these advantages comes the challenge of counteracting signal degradation caused by atmospheric turbulence in free-space environments. A fully coherent laser source experiences random phase delays along its traversing path in turbulent conditions forming a speckle pattern and lowering the received signal-to-noise ratio upon detection. Preliminary research has shown that receiver-side speckle contrast may be significantly reduced and signal-to-noise ratio increased accordingly through the use of a partially coherent light source. While dynamic diffusers and adaptive optics solutions have been proven effective, they also add expense and complexity to a system that relies on accessibility and robustness for successful implementation. A custom Hadamard diffractive matrix design is used to statically induce partial coherence in a transmitted beam to increase signal-to-noise ratio for experimental turbulence scenarios. Atmospheric phase screens are generated using an open-source software package and subsequently loaded into a spatial light modulator using nematic liquid crystals to modulate the phase.

  10. Quantum computing

    International Nuclear Information System (INIS)

    Steane, Andrew

    1998-01-01

    The subject of quantum computing brings together ideas from classical information theory, computer science, and quantum physics. This review aims to summarize not just quantum computing, but the whole subject of quantum information theory. Information can be identified as the most general thing which must propagate from a cause to an effect. It therefore has a fundamentally important role in the science of physics. However, the mathematical treatment of information, especially information processing, is quite recent, dating from the mid-20th century. This has meant that the full significance of information as a basic concept in physics is only now being discovered. This is especially true in quantum mechanics. The theory of quantum information and computing puts this significance on a firm footing, and has led to some profound and exciting new insights into the natural world. Among these are the use of quantum states to permit the secure transmission of classical information (quantum cryptography), the use of quantum entanglement to permit reliable transmission of quantum states (teleportation), the possibility of preserving quantum coherence in the presence of irreversible noise processes (quantum error correction), and the use of controlled quantum evolution for efficient computation (quantum computation). The common theme of all these insights is the use of quantum entanglement as a computational resource. It turns out that information theory and quantum mechanics fit together very well. In order to explain their relationship, this review begins with an introduction to classical information theory and computer science, including Shannon's theorem, error correcting codes, Turing machines and computational complexity. The principles of quantum mechanics are then outlined, and the Einstein, Podolsky and Rosen (EPR) experiment described. The EPR-Bell correlations, and quantum entanglement in general, form the essential new ingredient which distinguishes quantum from

  11. Quantum computing

    Energy Technology Data Exchange (ETDEWEB)

    Steane, Andrew [Department of Atomic and Laser Physics, University of Oxford, Clarendon Laboratory, Oxford (United Kingdom)

    1998-02-01

    The subject of quantum computing brings together ideas from classical information theory, computer science, and quantum physics. This review aims to summarize not just quantum computing, but the whole subject of quantum information theory. Information can be identified as the most general thing which must propagate from a cause to an effect. It therefore has a fundamentally important role in the science of physics. However, the mathematical treatment of information, especially information processing, is quite recent, dating from the mid-20th century. This has meant that the full significance of information as a basic concept in physics is only now being discovered. This is especially true in quantum mechanics. The theory of quantum information and computing puts this significance on a firm footing, and has led to some profound and exciting new insights into the natural world. Among these are the use of quantum states to permit the secure transmission of classical information (quantum cryptography), the use of quantum entanglement to permit reliable transmission of quantum states (teleportation), the possibility of preserving quantum coherence in the presence of irreversible noise processes (quantum error correction), and the use of controlled quantum evolution for efficient computation (quantum computation). The common theme of all these insights is the use of quantum entanglement as a computational resource. It turns out that information theory and quantum mechanics fit together very well. In order to explain their relationship, this review begins with an introduction to classical information theory and computer science, including Shannon's theorem, error correcting codes, Turing machines and computational complexity. The principles of quantum mechanics are then outlined, and the Einstein, Podolsky and Rosen (EPR) experiment described. The EPR-Bell correlations, and quantum entanglement in general, form the essential new ingredient which distinguishes quantum from

  12. A Composed Protocol of Quantum Identity Authentication Plus Quantum Key Distribution Based on Squeezed States

    International Nuclear Information System (INIS)

    Zhang Sheng; Wang Jian; Tang Chaojing; Zhang Quan

    2011-01-01

    It is established that a single quantum cryptography protocol usually cooperates with other cryptographic systems, such as an authentication system, in the real world. However, few protocols have been proposed on how to combine two or more quantum protocols. To fill this gap, we propose a composed quantum protocol, containing both quantum identity authentication and quantum key distribution, using squeezed states. Hence, not only the identity can be verified, but also a new private key can be generated by our new protocol. We also analyze the security under an optimal attack, and the efficiency, which is defined by the threshold of the tolerant error rate, using Gaussian error function. (general)

  13. The preparation problem in nonlinear extensions of quantum theory

    OpenAIRE

    Cavalcanti, Eric G.; Menicucci, Nicolas C.; Pienaar, Jacques L.

    2012-01-01

    Nonlinear modifications to the laws of quantum mechanics have been proposed as a possible way to consistently describe information processing in the presence of closed timelike curves. These have recently generated controversy due to possible exotic information-theoretic effects, including breaking quantum cryptography and radically speeding up both classical and quantum computers. The physical interpretation of such theories, however, is still unclear. We consider a large class of operationa...

  14. Hybrid Approach To Steganography System Based On Quantum Encryption And Chaos Algorithms

    Directory of Open Access Journals (Sweden)

    ZAID A. ABOD

    2018-01-01

    Full Text Available A hybrid scheme for secretly embedding image into a dithered multilevel image is presented. This work inputs both a cover image and secret image, which are scrambling and divided into groups to embedded together based on multiple chaos algorithms (Lorenz map, Henon map and Logistic map respectively. Finally, encrypt the embedded images by using one of the quantum cryptography mechanisms, which is quantum one time pad. The experimental results show that the proposed hybrid system successfully embedded images and combine with the quantum cryptography algorithms and gives high efficiency for secure communication.

  15. Visual cryptography for image processing and security theory, methods, and applications

    CERN Document Server

    Liu, Feng

    2014-01-01

    This unique book describes the fundamental concepts, theories and practice of visual cryptography. The design, construction, analysis, and application of visual cryptography schemes (VCSs) are discussed in detail. Original, cutting-edge research is presented on probabilistic, size invariant, threshold, concolorous, and cheating immune VCS. Features: provides a thorough introduction to the field; examines various common problems in visual cryptography, including the alignment, flipping, cheating, distortion, and thin line problems; reviews a range of VCSs, including XOR-based visual cryptograph

  16. Dember effect photodetectors and the effects of turbulence on free-space optical communication systems

    Science.gov (United States)

    Dikmelik, Yamac

    High-speed free-space optical communication systems have recently utilized components that have been developed for fiber-optic communication systems. The received laser beam in such a system must be coupled into a single-mode fiber at the input of a commercially available receiver module or a wavelength division demultiplexer. However, one effect of propagation through atmospheric turbulence is that the spatial coherence of a laser beam is degraded and the percentage of the available power that can be coupled into the single-mode fiber is limited. This dissertation presents a numerical evaluation of fiber coupling efficiency for laser light distorted by atmospheric turbulence. The results for weak fluctuation conditions provide the level of coupling efficiency that can be expected for a given turbulence strength. In addition, the results show that the link distance must be limited to 400 m under moderate turbulence conditions if the link budget requires a coupling efficiency of 0.1. We also investigate the use of a coherent fiber array as a receiver structure to improve the fiber coupling efficiency of a free-space optical communication system. Our numerical results show that a coherent fiber array that consists of seven subapertures would increase fiber coupling efficiency by a significant amount for representative turbulence conditions and link distances. The use of photo-emf detectors as elements of a wavefront sensor for an adaptive optics system is also considered as an alternative method of reducing the effects of turbulence on a free-space optical communication system. Dember and photo-emf currents are investigated in silicon photoconductive detectors both theoretically and experimentally. Our results show that Dember photocurrents dominate the response of high-purity silicon samples with top surface electrodes to a moving interference pattern. The use of surface electrodes leads to shadowed regions beneath the electrodes and Dember photocurrents appear

  17. Propagation and scattering of optical light beams in free space, in atmosphere and in biological media

    Science.gov (United States)

    Sahin, Serkan

    With their first production implemented around 1960's, lasers have afterwards proven to be excellent light sources in building the technology. Subsequently, it has been shown that the extraordinary properties of lasers are related to their coherence properties. Recent developments in optics make it possible to synthesize partially coherent light beams from fully coherent ones. In the last several decades it was seen that using partially coherent light sources may be advantageous, in the areas such as laser surface processing, fiber and free-space optical communications, and medical diagnostics. In this thesis, I study extensively the generation, the propagation in different media, and the scattering of partially coherent light beams with respect to their spectral polarization and coherence states. For instance, I analyze the evolution of recently introduced degree of cross-polarization of light fields in free space; then develop a novel partially coherent light source which acquires and keeps a flat intensity profile around the axis at any distance in the far field; and investigate the interaction of electromagnetic random light with the human eye lens. A part of the thesis treats the effect of atmospheric turbulence on random light beams. Due to random variations in the refractive index, atmospheric turbulence modulates all physical and statistical properties of propagating beams. I have explored the possibility of employing the polarimetric domain of the beam for scintillation reduction, which positively affects the performance of free-space communication systems. I also discuss novel techniques for the sensing of rough targets in the turbulent atmosphere by polarization and coherence properties of light. The other contribution to the thesis is the investigation of light scattering from deterministic or random collections of particles, within the validity of first Born approximation. In the case of a random collection, I introduce and model the new quantity

  18. Learning Perfectly Secure Cryptography to Protect Communications with Adversarial Neural Cryptography

    Directory of Open Access Journals (Sweden)

    Murilo Coutinho

    2018-04-01

    Full Text Available Researches in Artificial Intelligence (AI have achieved many important breakthroughs, especially in recent years. In some cases, AI learns alone from scratch and performs human tasks faster and better than humans. With the recent advances in AI, it is natural to wonder whether Artificial Neural Networks will be used to successfully create or break cryptographic algorithms. Bibliographic review shows the main approach to this problem have been addressed throughout complex Neural Networks, but without understanding or proving the security of the generated model. This paper presents an analysis of the security of cryptographic algorithms generated by a new technique called Adversarial Neural Cryptography (ANC. Using the proposed network, we show limitations and directions to improve the current approach of ANC. Training the proposed Artificial Neural Network with the improved model of ANC, we show that artificially intelligent agents can learn the unbreakable One-Time Pad (OTP algorithm, without human knowledge, to communicate securely through an insecure communication channel. This paper shows in which conditions an AI agent can learn a secure encryption scheme. However, it also shows that, without a stronger adversary, it is more likely to obtain an insecure one.

  19. Learning Perfectly Secure Cryptography to Protect Communications with Adversarial Neural Cryptography.

    Science.gov (United States)

    Coutinho, Murilo; de Oliveira Albuquerque, Robson; Borges, Fábio; García Villalba, Luis Javier; Kim, Tai-Hoon

    2018-04-24

    Researches in Artificial Intelligence (AI) have achieved many important breakthroughs, especially in recent years. In some cases, AI learns alone from scratch and performs human tasks faster and better than humans. With the recent advances in AI, it is natural to wonder whether Artificial Neural Networks will be used to successfully create or break cryptographic algorithms. Bibliographic review shows the main approach to this problem have been addressed throughout complex Neural Networks, but without understanding or proving the security of the generated model. This paper presents an analysis of the security of cryptographic algorithms generated by a new technique called Adversarial Neural Cryptography (ANC). Using the proposed network, we show limitations and directions to improve the current approach of ANC. Training the proposed Artificial Neural Network with the improved model of ANC, we show that artificially intelligent agents can learn the unbreakable One-Time Pad (OTP) algorithm, without human knowledge, to communicate securely through an insecure communication channel. This paper shows in which conditions an AI agent can learn a secure encryption scheme. However, it also shows that, without a stronger adversary, it is more likely to obtain an insecure one.

  20. Quantum systems, channels, information. A mathematical introduction

    Energy Technology Data Exchange (ETDEWEB)

    Holevo, Alexander S.

    2012-07-01

    The subject of this book is theory of quantum system presented from information science perspective. The central role is played by the concept of quantum channel and its entropic and information characteristics. Quantum information theory gives a key to understanding elusive phenomena of quantum world and provides a background for development of experimental techniques that enable measuring and manipulation of individual quantum systems. This is important for the new efficient applications such as quantum computing, communication and cryptography. Research in the field of quantum informatics, including quantum information theory, is in progress in leading scientific centers throughout the world. This book gives an accessible, albeit mathematically rigorous and self-contained introduction to quantum information theory, starting from primary structures and leading to fundamental results and to exiting open problems.

  1. Quantum mechanics a modern development

    CERN Document Server

    Ballentine, Leslie E

    2015-01-01

    Although there are many textbooks that deal with the formal apparatus of quantum mechanics (QM) and its application to standard problems, none take into account the developments in the foundations of the subject which have taken place in the last few decades. There are specialized treatises on various aspects of the foundations of QM, but none that integrate those topics with the standard material. This book aims to remove that unfortunate dichotomy, which has divorced the practical aspects of the subject from the interpretation and broader implications of the theory. In this edition a new chapter on quantum information is added. As the topic is still in a state of rapid development, a comprehensive treatment is not feasible. The emphasis is on the fundamental principles and some key applications, including quantum cryptography, teleportation of states, and quantum computing. The impact of quantum information theory on the foundations of quantum mechanics is discussed. In addition, there are minor revisions ...

  2. Free-Space Optical Communications: Capacity Bounds, Approximations, and a New Sphere-Packing Perspective

    KAUST Repository

    Chaaban, Anas; Morvan, Jean-Marie; Alouini, Mohamed-Slim

    2016-01-01

    The capacity of the free-space optical channel is studied. A new recursive approach for bounding the capacity of the channel based on sphere-packing is proposed. This approach leads to new capacity upper bounds for a channel with a peak intensity constraint or an average intensity constraint. Under an average constraint only, the derived bound is tighter than an existing sphere-packing bound derived earlier by Farid and Hranilovic. The achievable rate of a truncated-Gaussian input distribution is also derived. It is shown that under both average and peak constraints, this achievable rate and the sphere-packing bounds are within a small gap at high SNR, leading to a simple high-SNR capacity approximation. Simple fitting functions that capture the best known achievable rate for the channel are provided. These functions can be of practical importance especially for the study of systems operating under atmospheric turbulence and misalignment conditions.

  3. System and method that suppresses intensity fluctuations for free space high-speed optical communication

    Science.gov (United States)

    Berman, Gennady P [Los Alamos, NM; Bishop, Alan R [Los Alamos, NM; Nguyen, Dinh C [Los Alamos, NM; Chernobrod, Boris M [Santa Fe, NM; Gorshkov, Vacheslav N [Kiev, UA

    2009-10-13

    A high-speed (Gbps), free space optical communication system is based on spectral encoding of radiation from a wide band light source, such as a laser. By using partially coherent laser beams in combination with a relatively slow photosensor, scintillations can be suppressed by orders of magnitude for distances of more than 10 km. To suppress the intensity fluctuations due to atmospheric turbulence, a source with partial transverse coherence in combination with slow response time photodetector is used. Information is encoded in the spectral domain of a wideband optical source by modulation of spectral amplitudes. A non-coherent light source with wide spectrum (an LED, for example) may be used for high-speed communication over short (less than about a mile) distances.

  4. Differential phase-shift keying and channel equalization in free space optical communication system

    Science.gov (United States)

    Zhang, Dai; Hao, Shiqi; Zhao, Qingsong; Wan, Xiongfeng; Xu, Chenlu

    2018-01-01

    We present the performance benefits of differential phase-shift keying (DPSK) modulation in eliminating influence from atmospheric turbulence, especially for coherent free space optical (FSO) communication with a high communication rate. Analytic expression of detected signal is derived, based on which, homodyne detection efficiency is calculated to indicate the performance of wavefront compensation. Considered laser pulses always suffer from atmospheric scattering effect by clouds, intersymbol interference (ISI) in high-speed FSO communication link is analyzed. Correspondingly, the channel equalization method of a binormalized modified constant modulus algorithm based on set-membership filtering (SM-BNMCMA) is proposed to solve the ISI problem. Finally, through the comparison with existing channel equalization methods, its performance benefits of both ISI elimination and convergence speed are verified. The research findings have theoretical significance in a high-speed FSO communication system.

  5. Mobile free-space optical communications: a feasibility study of various battlefield scenarios

    Science.gov (United States)

    Harris, Alan; Al-Akkoumi, Mouhammad K.; Sluss, James J., Jr.

    2012-06-01

    Free Space Optics (FSO) technology was originally envisioned to be a viable solution for the provision of high bandwidth optical connectivity in the last mile of today's telecommunications infrastructure. Due to atmospheric limitations inherent to FSO technology, FSO is now widely envisioned as a solution for the provision of high bandwidth, temporary mobile communications links. The need for FSO communications links will increase as mobility is introduced to this technology. In this paper, a theoretical solution for adding mobility to FSO communication links is introduced. Three-dimensional power estimation studies are presented to represent mobile FSO transmission under various weather conditions. Three wavelengths, 0.85, 1.55 and 10 um, are tested and compared to illustrate the pros and cons of each source wavelength used for transmission, depending on prevalent weather conditions and atmospheric turbulence conditions. A simulation analysis of the transmission properties of the source wavelengths used in the study is shown.

  6. Ergodic Capacity Analysis of Free-Space Optical Links with Nonzero Boresight Pointing Errors

    KAUST Repository

    Ansari, Imran Shafique

    2015-04-01

    A unified capacity analysis of a free-space optical (FSO) link that accounts for nonzero boresight pointing errors and both types of detection techniques (i.e. intensity modulation/ direct detection as well as heterodyne detection) is addressed in this work. More specifically, an exact closed-form expression for the moments of the end-to-end signal-to-noise ratio (SNR) of a single link FSO transmission system is presented in terms of well-known elementary functions. Capitalizing on these new moments expressions, we present approximate and simple closedform results for the ergodic capacity at high and low SNR regimes. All the presented results are verified via computer-based Monte-Carlo simulations.

  7. Unified performance analysis of hybrid-ARQ with incremental redundancy over free-space optical channels

    KAUST Repository

    Zedini, Emna

    2014-09-01

    In this paper, we carry out a unified performance analysis of hybrid automatic repeat request (HARQ) with incremental redundancy (IR) from an information theoretic perspective over a point-to-point free-space optical (FSO) system. First, we introduce a novel unified expression for the distribution of a single FSO link modeled by the Gamma fading that accounts for pointing errors subject to both types of detection techniques at the receiver side (i.e. heterodyne detection and intensity modulation with direct detection (IM/DD)). Then, we provide analytical expressions for the outage probability, the average number of transmissions, and the average transmission rate for HARQ with IR, assuming a maximum number of rounds for the HARQ protocol. In our study, the communication rate per HARQ round is constant. Our analysis demonstrates the importance of HARQ in improving the performance and reliability of FSO communication systems. All the given results are verified via computer-based Monte-Carlo simulations.

  8. Free-Space Optical Communications: Capacity Bounds, Approximations, and a New Sphere-Packing Perspective

    KAUST Repository

    Chaaban, Anas

    2016-02-03

    The capacity of the free-space optical channel is studied. A new recursive approach for bounding the capacity of the channel based on sphere-packing is proposed. This approach leads to new capacity upper bounds for a channel with a peak intensity constraint or an average intensity constraint. Under an average constraint only, the derived bound is tighter than an existing sphere-packing bound derived earlier by Farid and Hranilovic. The achievable rate of a truncated-Gaussian input distribution is also derived. It is shown that under both average and peak constraints, this achievable rate and the sphere-packing bounds are within a small gap at high SNR, leading to a simple high-SNR capacity approximation. Simple fitting functions that capture the best known achievable rate for the channel are provided. These functions can be of practical importance especially for the study of systems operating under atmospheric turbulence and misalignment conditions.

  9. 850-nm hybrid fiber/free-space optical communications using orbital angular momentum modes

    DEFF Research Database (Denmark)

    Jurado-Navas, Antonio; Tatarczak, Anna; Lu, Xiaofeng

    2015-01-01

    Light beams can carry orbital angular momentum (OAM) associated to the helicity of their phasefronts. These OAM modes can be employed to encode information onto a laser beam for transmitting not only in a fiber link but also in a free-space optical (FSO) one. Regarding this latter scenario, FSO...... communications are considered as an alternative and promising mean complementing the traditional optical communications in many applications where the use of fiber cable is not justified. This next generation FSO communication systems have attracted much interest recently, and the inclusion of beams carrying OAM...... modes can be seen as an efficient solution to increase the capacity and the security in the link. In this paper, we discuss an experimental demonstration of a proposal for next generation FSO communication system where a light beam carrying different OAM modes and affected by M turbulence is coupled...

  10. Performance analysis of coherent free space optical communications with sequential pyramid wavefront sensor

    Science.gov (United States)

    Liu, Wei; Yao, Kainan; Chen, Lu; Huang, Danian; Cao, Jingtai; Gu, Haijun

    2018-03-01

    Based-on the previous study on the theory of the sequential pyramid wavefront sensor (SPWFS), in this paper, the SPWFS is first applied to the coherent free space optical communications (FSOC) with more flexible spatial resolution and higher sensitivity than the Shack-Hartmann wavefront sensor, and with higher uniformity of intensity distribution and much simpler than the pyramid wavefront sensor. Then, the mixing efficiency (ME) and the bit error rate (BER) of the coherent FSOC are analyzed during the aberrations correction through numerical simulation with binary phase shift keying (BPSK) modulation. Finally, an experimental AO system based-on SPWFS is setup, and the experimental data is used to analyze the ME and BER of homodyne detection with BPSK modulation. The results show that the AO system based-on SPWFS can increase ME and decrease BER effectively. The conclusions of this paper provide a new method of wavefront sensing for designing the AO system for a coherent FSOC system.

  11. Design of free-space optical transmission system in computer tomography equipment

    Science.gov (United States)

    Liu, Min; Fu, Weiwei; Zhang, Tao

    2018-04-01

    Traditional computer tomography (CT) based on capacitive coupling cannot satisfy the high data rate transmission requirement. We design and experimentally demonstrate a free-space optical transmission system for CT equipment at a data rate of 10 Gb / s. Two interchangeable sections of 12 pieces of fiber with equal length is fabricated and tested by our designed laser phase distance measurement system. By locating the 12 collimators in the edge of the circle wheel evenly, the optical propagation characteristics for the 12 wired and wireless paths are similar, which can satisfy the requirement of high-speed CT transmission system. After bit error rate (BER) measurement in several conditions, the BER performances are below the value of 10 - 11, which has the potential in the future application scenario of CT equipment.

  12. Optical Nano-antennae as Compact and Efficient Couplers from Free-space to Waveguide Modes

    DEFF Research Database (Denmark)

    Zenin, Vladimir A.; Malureanu, Radu; Volkov, Valentyn

    2015-01-01

    Optical nano-antennae are one of the possible solutions for coupling free-space radiation into subwavelength waveguides. Our efforts were concentrated on coupling between an optical fibre and a plasmonic slot waveguide. Such coupling is still an issue to be solved in order to advance the use...... of plasmonic waveguides for optical interconnects. During the talk, we will present our modelling optimisation, fabrication and measurement of the nano-antennae functionality. For the modelling part, we used CST Microwave studio for optimising the antenna geometry. Various antennae were modelled and fabricated....... The fabrication was based on electron beam lithography and lift-off processes. The measurements were performed with scattering scanning near-field microscope and allowed the retrieval of both amplitude and phase of the propagating plasmon. The obtained values agree very well with the theoretically predicted ones...

  13. ''Free-space'' boundary conditions for the time-dependent wave equation

    International Nuclear Information System (INIS)

    Lindman, E.L.

    1975-01-01

    Boundary conditions for the discrete wave equation which act like an infinite region of free space in contact with the computational region can be constructed using projection operators. Propagating and evanescent waves coming from within the computational region generate no reflected waves as they cross the boundary. At the same time arbitrary waves may be launched into the computational region. Well known projection operators for one-dimensional waves may be used for this purpose in one dimension. Extensions of these operators to higher dimensions along with numerically efficient approximations to them are described for higher-dimensional problems. The separation of waves into ingoing and outgoing waves inherent in these boundary conditions greatly facilitates diagnostics

  14. A multi-rate DPSK modem for free-space laser communications

    Science.gov (United States)

    Spellmeyer, N. W.; Browne, C. A.; Caplan, D. O.; Carney, J. J.; Chavez, M. L.; Fletcher, A. S.; Fitzgerald, J. J.; Kaminsky, R. D.; Lund, G.; Hamilton, S. A.; Magliocco, R. J.; Mikulina, O. V.; Murphy, R. J.; Rao, H. G.; Scheinbart, M. S.; Seaver, M. M.; Wang, J. P.

    2014-03-01

    The multi-rate DPSK format, which enables efficient free-space laser communications over a wide range of data rates, is finding applications in NASA's Laser Communications Relay Demonstration. We discuss the design and testing of an efficient and robust multi-rate DPSK modem, including aspects of the electrical, mechanical, thermal, and optical design. The modem includes an optically preamplified receiver, an 0.5-W average power transmitter, a LEON3 rad-hard microcontroller that provides the command and telemetry interface and supervisory control, and a Xilinx Virtex-5 radhard reprogrammable FPGA that both supports the high-speed data flow to and from the modem and controls the modem's analog and digital subsystems. For additional flexibility, the transmitter and receiver can be configured to support operation with multi-rate PPM waveforms.

  15. Free-space optical communications with peak and average constraints: High SNR capacity approximation

    KAUST Repository

    Chaaban, Anas

    2015-09-07

    The capacity of the intensity-modulation direct-detection (IM-DD) free-space optical channel with both average and peak intensity constraints is studied. A new capacity lower bound is derived by using a truncated-Gaussian input distribution. Numerical evaluation shows that this capacity lower bound is nearly tight at high signal-to-noise ratio (SNR), while it is shown analytically that the gap to capacity upper bounds is a small constant at high SNR. In particular, the gap to the high-SNR asymptotic capacity of the channel under either a peak or an average constraint is small. This leads to a simple approximation of the high SNR capacity. Additionally, a new capacity upper bound is derived using sphere-packing arguments. This bound is tight at high SNR for a channel with a dominant peak constraint.

  16. Performance Analysis of Free-Space Optical Communication Systems With Multiuser Diversity Over Atmospheric Turbulence Channels

    KAUST Repository

    Yang, Liang

    2014-04-01

    Free-space optical (FSO) communication has become a cost-effective method to provide high data rates. However, the turbulence-induced fading limits its application to short-range applications. To address this, we propose a multiuser diversity (MD) FSO scheme in which the Nth best user is selected and the channel fluctuations can be effectively exploited to produce a selection diversity gain. More specifically, we first present the statistics analysis for the considered system over both weak and strong atmospheric turbulence channels. Based on these statistics, the outage probability, bit-error rate performance, average capacity, diversity order, and coverage are analyzed. Results show that the diversity order for the gamma-gamma fading is N min{α, β}/2, where N is the number of users, and α and β are the channel fading parameters related to the effective atmospheric conditions of the link.

  17. Embracing the quantum limit in silicon computing.

    Science.gov (United States)

    Morton, John J L; McCamey, Dane R; Eriksson, Mark A; Lyon, Stephen A

    2011-11-16

    Quantum computers hold the promise of massive performance enhancements across a range of applications, from cryptography and databases to revolutionary scientific simulation tools. Such computers would make use of the same quantum mechanical phenomena that pose limitations on the continued shrinking of conventional information processing devices. Many of the key requirements for quantum computing differ markedly from those of conventional computers. However, silicon, which plays a central part in conventional information processing, has many properties that make it a superb platform around which to build a quantum computer. © 2011 Macmillan Publishers Limited. All rights reserved

  18. Hyperon interaction in free space and nuclear matter within a SU(3) based meson exchange model

    Energy Technology Data Exchange (ETDEWEB)

    Dhar, Madhumita

    2016-06-15

    To establish the connection between free space and in-medium hyperon-nucleon interactions is the central issue of this thesis. The guiding principle is flavor SU(3) symmetry which is exploited at various levels. In first step hyperon-nucleon and hyperon- hyperon interaction boson exchange potential in free space are introduced. A new parameter set applicable for the complete baryon octet has been derived leading to an updated one-boson- exchange model, utilizing SU(3) flavor symmetry, optimizing the number of free parameters involved, and revising the set of mesons included. The scalar, pseudoscalar, and vector SU(3) meson octets are taken into account. T-matrices are calculated by solving numerically coupled linear systems of Lippmann-Schwinger equations obtained from a 3-D reduced Bethe-Salpeter equation. Coupling constants were determined by χ{sup 2} fits to the world set of scattering data. A good description of the few available data is achieved within the imposed SU(3) constraints. Having at hand a consistently derived vacuum interaction we extend the approach next to investigations of the in-medium properties of hyperon interaction, avoiding any further adjustments. Medium effect in infinite nuclear matter are treated microscopically by recalculating T-matrices by an medium-modified system of Lippmann-Schwinger equations. A particular important role is played by the Pauli projector accounting for the exclusion principle. The presence of a background medium induces a weakening of the vacuum interaction amplitudes. Especially coupled channel mixing is found to be affected sensitively by medium. Investigation on scattering lengths and effective range parameters are revealing the density dependence of the interaction on a quantitative level.

  19. Non-Mechanical Beam Steering in Free-Space Optical Communication Transceivers

    Science.gov (United States)

    Shortt, Kevin

    Free-space optical communications systems are a rapidly growing field as they carry many of the advantages of traditional fibre-based communications systems without the added investment of installing complex infrastructure. Moreover, these systems are finding key niches in mobile platforms in order to take advantage of the increased bandwidth over traditional RF systems. Of course, the inevitable problem of tracking arises when dealing with mobile stations. To compound the problem in the case of communications to low Earth or geosynchronous orbits, FSOC systems typically operate with tightly confined beams over great distances often requiring pointing accuracies on the order of micro-radians or smaller. Mechanisms such as gimbal mounts and fine-steering mirrors are the usual candidates for platform stabilization, however, these clearly have substantial power requirements and inflate the mass of the system. Spatial light modulators (also known as optical phased arrays), on the other hand, offer a suitable alternative for beam-pointing stabilization. Some of the advantages of spatial light modulators over fine-steering mirrors include programmable multiple simultaneous beams, dynamic focus/defocus and moderate to excellent optical power handling capability. This thesis serves as an investigation into the implementation of spatial light modulators as a replacement for traditional fine-steering mirrors in the fine-pointing subsystem. In particular, pointing accuracy and scanning ability will be highlighted as performance metrics in the context of a variety of communication scenarios. Keywords: Free-space optical communications, beam steering, fine-steering mirror, spatial light modulator, optical phased array.

  20. Free-Space Measurements of Dielectrics and Three-Dimensional Periodic Metamaterials

    Science.gov (United States)

    Kintner, Clifford E.

    This thesis presents the free-space measurements of a periodic metamaterial structure. The metamaterial unit cell consists of two dielectric sheets intersecting at 90 degrees. The dielectric is a polyetherimide-based material 0.001" thick. Each sheet has a copper capacitively-loaded loop (CLL) structure on the front and a cut-wire structure on the back. Foam material is used to support the unit cells. The unit cell repeats 40 times in the x-direction, 58 times in the y-direction and 5 times in the z-direction. The sample measures 12" x 12" x 1" in total. We use a free-space broadband system comprised of a pair of dielectric-lens horn antennas with bandwidth from 5.8 GHz to 110 GHz, which are connected to a HP PNA series network analyzer. The dielectric lenses focus the incident beam to a footprint measuring 1 wavelength by 1 wavelength. The sample holder is positioned at the focal point between the two antennas. In this work, the coefficients of transmission and reflection (the S-parameters S21 and S11) are measured at frequencies from 12.4 GHz up to 30 GHz. Simulations are used to validate the measurements, using the Ansys HFSS commercial software package on the Arkansas High Performance Computing Center cluster. The simulation results successfully validate the S-parameters measurements, in particular the amplitudes. An algorithm based on the Nicolson-Ross-Weir (NRW) method is implemented to extract the permittivity and permeability values of the metamaterial under test. The results show epsilon-negative, mu-negative and double-negative parameters within the measured frequency range.

  1. On the Performance Analysis of Free-Space Optical Links under Generalized Turbulence and Misalignment Models

    KAUST Repository

    AlQuwaiee, Hessa

    2016-11-01

    One of the potential solutions to the radio frequency (RF) spectrum scarcity problem is optical wireless communications (OWC), which utilizes the unlicensed optical spectrum. Long-range outdoor OWC are usually referred to in the literature as free-space optical (FSO) communications. Unlike RF systems, FSO is immune to interference and multi-path fading. Also, the deployment of FSO systems is flexible and much faster than optical fibers. These attractive features make FSO applicable for broadband wireless transmission such as optical fiber backup, metropolitan area network, and last mile access. Although FSO communication is a promising technology, it is negatively affected by two physical phenomenon, namely, scintillation due to atmospheric turbulence and pointing errors. These two critical issues have prompted intensive research in the last decade. To quantify the effect of these two factors on FSO system performance, we need effective mathematical models. In this work, we propose and study a generalized pointing error model based on the Beckmann distribution. Then, we aim to generalize the FSO channel model to span all turbulence conditions from weak to strong while taking pointing errors into consideration. Since scintillation in FSO is analogous to the fading phenomena in RF, diversity has been proposed too to overcome the effect of irradiance fluctuations. Thus, several combining techniques of not necessarily independent dual-branch free-space optical links were investigated over both weak and strong turbulence channels in the presence of pointing errors. On another front, improving the performance, enhancing the capacity and reducing the delay of the communication link has been the motivation of any newly developed schemes, especially for backhauling. Recently, there has been a growing interest in practical systems to integrate RF and FSO technologies to solve the last mile bottleneck. As such, we also study in this thesis asymmetric an RF-FSO dual-hop relay

  2. Enemy-free space and habitat-specific host specialization in a butterfly.

    Science.gov (United States)

    Wiklund, Christer; Friberg, Magne

    2008-08-01

    The majority of herbivorous insects have relatively specialized food habits. This suggests that specialization has some advantage(s) over generalization. Traditionally, feeding specialization has been thought to be linked to digestive or other food-related physiological advantages, but recent theory suggests that generalist natural enemies of herbivorous insects can also provide a major selective pressure for restricted host plant range. The European swallowtail butterfly Papilio machaon utilizes various plants in the Apiaceae family as hosts, but is an ecological specialist being monophagous on Angelica archangelica in southern Sweden. This perennial monocarp grows in three seaside habitat types: (1) on the barren rocky shore in the absence of any surrounding vegetation, (2) on the rocky shore with some surrounding vegetation, and (3) on species-rich meadows. The rocky shore habitat harbors few invertebrate generalist predators, whereas a number of invertebrate predators abound in the meadowland habitat. Here, we test the importance of enemy-free space for feeding specialization in Papilio machaon by assessing survival of larvae placed by hand on A. archangelica in each of the three habitat types, and by assessing the habitat-specificity of adult female egg-laying behavior by recording the distribution of eggs laid by free-flying adult females among the three habitat types. Larval survival was substantially higher in the rocky shore habitat than in the meadowland and significantly higher on host plants without surrounding vegetation on the rocky shore. Eggs laid by free-flying females were found in all three habitat types, but were significantly more frequent in the rocky shore habitat, suggesting that females prefer to lay eggs in the habitat type where offspring survival is highest. These results show that larval survivorship on the same host plant species can be strongly habitat-specific, and suggest that enemy-free space is an underlying factor that drives

  3. Electronic Voting Protocol Using Identity-Based Cryptography

    Directory of Open Access Journals (Sweden)

    Gina Gallegos-Garcia

    2015-01-01

    Full Text Available Electronic voting protocols proposed to date meet their properties based on Public Key Cryptography (PKC, which offers high flexibility through key agreement protocols and authentication mechanisms. However, when PKC is used, it is necessary to implement Certification Authority (CA to provide certificates which bind public keys to entities and enable verification of such public key bindings. Consequently, the components of the protocol increase notably. An alternative is to use Identity-Based Encryption (IBE. With this kind of cryptography, it is possible to have all the benefits offered by PKC, without neither the need of certificates nor all the core components of a Public Key Infrastructure (PKI. Considering the aforementioned, in this paper we propose an electronic voting protocol, which meets the privacy and robustness properties by using bilinear maps.

  4. Two-phase hybrid cryptography algorithm for wireless sensor networks

    Directory of Open Access Journals (Sweden)

    Rawya Rizk

    2015-12-01

    Full Text Available For achieving security in wireless sensor networks (WSNs, cryptography plays an important role. In this paper, a new security algorithm using combination of both symmetric and asymmetric cryptographic techniques is proposed to provide high security with minimized key maintenance. It guarantees three cryptographic primitives, integrity, confidentiality and authentication. Elliptical Curve Cryptography (ECC and Advanced Encryption Standard (AES are combined to provide encryption. XOR-DUAL RSA algorithm is considered for authentication and Message Digest-5 (MD5 for integrity. The results show that the proposed hybrid algorithm gives better performance in terms of computation time, the size of cipher text, and the energy consumption in WSN. It is also robust against different types of attacks in the case of image encryption.

  5. Online Voting System Based on Image Steganography and Visual Cryptography

    Directory of Open Access Journals (Sweden)

    Biju Issac

    2017-01-01

    Full Text Available This paper discusses the implementation of an online voting system based on image steganography and visual cryptography. The system was implemented in Java EE on a web-based interface, with MySQL database server and Glassfish application server as the backend. After considering the requirements of an online voting system, current technologies on electronic voting schemes in published literature were examined. Next, the cryptographic and steganography techniques best suited for the requirements of the voting system were chosen, and the software was implemented. We have incorporated in our system techniques like the password hashed based scheme, visual cryptography, F5 image steganography and threshold decryption cryptosystem. The analysis, design and implementation phase of the software development of the voting system is discussed in detail. We have also used a questionnaire survey and did the user acceptance testing of the system.

  6. Electronic Voting Protocol Using Identity-Based Cryptography.

    Science.gov (United States)

    Gallegos-Garcia, Gina; Tapia-Recillas, Horacio

    2015-01-01

    Electronic voting protocols proposed to date meet their properties based on Public Key Cryptography (PKC), which offers high flexibility through key agreement protocols and authentication mechanisms. However, when PKC is used, it is necessary to implement Certification Authority (CA) to provide certificates which bind public keys to entities and enable verification of such public key bindings. Consequently, the components of the protocol increase notably. An alternative is to use Identity-Based Encryption (IBE). With this kind of cryptography, it is possible to have all the benefits offered by PKC, without neither the need of certificates nor all the core components of a Public Key Infrastructure (PKI). Considering the aforementioned, in this paper we propose an electronic voting protocol, which meets the privacy and robustness properties by using bilinear maps.

  7. Conference on Algebraic Geometry for Coding Theory and Cryptography

    CERN Document Server

    Lauter, Kristin; Walker, Judy

    2017-01-01

    Covering topics in algebraic geometry, coding theory, and cryptography, this volume presents interdisciplinary group research completed for the February 2016 conference at the Institute for Pure and Applied Mathematics (IPAM) in cooperation with the Association for Women in Mathematics (AWM). The conference gathered research communities across disciplines to share ideas and problems in their fields and formed small research groups made up of graduate students, postdoctoral researchers, junior faculty, and group leaders who designed and led the projects. Peer reviewed and revised, each of this volume's five papers achieves the conference’s goal of using algebraic geometry to address a problem in either coding theory or cryptography. Proposed variants of the McEliece cryptosystem based on different constructions of codes, constructions of locally recoverable codes from algebraic curves and surfaces, and algebraic approaches to the multicast network coding problem are only some of the topics covered in this vo...

  8. Modern cryptography and elliptic curves a beginner's guide

    CERN Document Server

    Shemanske, Thomas R

    2017-01-01

    This book offers the beginning undergraduate student some of the vista of modern mathematics by developing and presenting the tools needed to gain an understanding of the arithmetic of elliptic curves over finite fields and their applications to modern cryptography. This gradual introduction also makes a significant effort to teach students how to produce or discover a proof by presenting mathematics as an exploration, and at the same time, it provides the necessary mathematical underpinnings to investigate the practical and implementation side of elliptic curve cryptography (ECC). Elements of abstract algebra, number theory, and affine and projective geometry are introduced and developed, and their interplay is exploited. Algebra and geometry combine to characterize congruent numbers via rational points on the unit circle, and group law for the set of points on an elliptic curve arises from geometric intuition provided by Bézout's theorem as well as the construction of projective space. The structure of the...

  9. ID based cryptography for secure cloud data storage

    OpenAIRE

    Kaaniche , Nesrine; Boudguiga , Aymen; Laurent , Maryline

    2013-01-01

    International audience; This paper addresses the security issues of storing sensitive data in a cloud storage service and the need for users to trust the commercial cloud providers. It proposes a cryptographic scheme for cloud storage, based on an original usage of ID-Based Cryptography. Our solution has several advantages. First, it provides secrecy for encrypted data which are stored in public servers. Second, it offers controlled data access and sharing among users, so that unauthorized us...

  10. An Incomplete Cryptography based Digital Rights Management with DCFF

    OpenAIRE

    Thanh, Ta Minh; Iwakiri, Munetoshi

    2014-01-01

    In general, DRM (Digital Rights Management) system is responsible for the safe distribution of digital content, however, DRM system is achieved with individual function modules of cryptography, watermarking and so on. In this typical system flow, it has a problem that all original digital contents are temporarily disclosed with perfect condition via decryption process. In this paper, we propose the combination of the differential codes and fragile fingerprinting (DCFF) method based on incompl...

  11. Influence of wind speed on free space optical communication performance for Gaussian beam propagation through non Kolmogorov strong turbulence

    International Nuclear Information System (INIS)

    Deng Peng; Yuan Xiuhua; Zeng Yanan; Zhao Ming; Luo Hanjun

    2011-01-01

    In free-space optical communication links, atmospheric turbulence causes fluctuations in both the intensity and the phase of the received signal, affecting link performance. Most theoretical treatments have been described by Kolmogorov's power spectral density model through weak turbulence with constant wind speed. However, several experiments showed that Kolmogorov theory is sometimes incomplete to describe atmospheric turbulence properly, especially through the strong turbulence with variable wind speed, which is known to contribute significantly to the turbulence in the atmosphere. We present an optical turbulence model that incorporates into variable wind speed instead of constant value, a non-Kolmogorov power spectrum that uses a generalized exponent instead of constant standard exponent value 11/3, and a generalized amplitude factor instead of constant value 0.033. The free space optical communication performance for a Gaussian beam wave of scintillation index, mean signal-to-noise ratio , and mean bit error rate , have been derived by extended Rytov theory in non-Kolmogorov strong turbulence. And then the influence of wind speed variations on free space optical communication performance has been analyzed under different atmospheric turbulence intensities. The results suggest that the effects of wind speed variation through non-Kolmogorov turbulence on communication performance are more severe in many situations and need to be taken into account in free space optical communication. It is anticipated that this work is helpful to the investigations of free space optical communication performance considering wind speed under severe weather condition in the strong atmospheric turbulence.

  12. Generalized free-space diffuse photon transport model based on the influence analysis of a camera lens diaphragm.

    Science.gov (United States)

    Chen, Xueli; Gao, Xinbo; Qu, Xiaochao; Chen, Duofang; Ma, Xiaopeng; Liang, Jimin; Tian, Jie

    2010-10-10

    The camera lens diaphragm is an important component in a noncontact optical imaging system and has a crucial influence on the images registered on the CCD camera. However, this influence has not been taken into account in the existing free-space photon transport models. To model the photon transport process more accurately, a generalized free-space photon transport model is proposed. It combines Lambertian source theory with analysis of the influence of the camera lens diaphragm to simulate photon transport process in free space. In addition, the radiance theorem is also adopted to establish the energy relationship between the virtual detector and the CCD camera. The accuracy and feasibility of the proposed model is validated with a Monte-Carlo-based free-space photon transport model and physical phantom experiment. A comparison study with our previous hybrid radiosity-radiance theorem based model demonstrates the improvement performance and potential of the proposed model for simulating photon transport process in free space.

  13. Eight-channel video broadcast feed service using free-space optical wireless technology at the Sydney 2000 Olympic Games

    Science.gov (United States)

    Szajowski, Paul F.; Rigas, A. J.; Robinson, J. W.; Nykolak, Gerald; Paulson, Bruce D.; Tourgee, G. E.; Auborn, James J.

    2001-02-01

    12 Terrestrial 1550 nm WDM free-space optical communication systems have been demonstrated to provide a viable means to transport data, voice and video channels for point-to-point applications without the use of optical fiber. Key features of free-space optical transmission systems are their ability to utilize present day telecommunication components such as: laser diode transmitters, high-power optical amplifiers operating within the 1550 nm optical transmission window and high-sensitivity optical receivers designed for multi-Giga- bit data rates. In this paper, we report on details of the world's first field test, demonstrating real time video transmission of eight uncompressed standard-definition (SD) video channels operating at an aggregate data rate of 1.485 Gb/s over a 0.89 km terrestrial free-space link. This data link was used in support of the 2000 Olympic games held recently in Sydney, Australia. Results from this eight- channel SD terrestrial free-space laser communications systems are presented. The transmission system operated error-free continuously from September 14, 2000 until October 1, 2000, twenty-four hours a day, throughout the coverage of the games. Modeling results predict that free- space SD video transmission systems can be designed and operated over significant link distances under nominal visibility conditions.

  14. Frodo: Take off the ring! Practical, quantum-secure key exchange from LWE

    NARCIS (Netherlands)

    J. Bos; C.J. Costello (Craig); L. Ducas (Léo); Mironov (I); Naehrig (Michael); Nikolaendo (Valieria); Ragghunathan (Ananth); Stebila (Douglas)

    2016-01-01

    textabstractLattice-based cryptography offers some of the most attractive primitives believed to be resistant to quantum computers. Following increasing interest from both companies and government agencies in building quantum computers, a number of works have proposed instantiations of practical

  15. Investigating Quantum Modulation States

    Science.gov (United States)

    2016-03-01

    Coherent state quantum data encryption is highly interoperable with current classical optical infrastructure in both fiber and free space optical networks...hub’s field of regard has a transmit/receive module that are endpoints of the Lyot filter stage tree within the hub’s backend electro-optics control... mobile airborne and space-borne networking. Just like any laser communication technology, QC links are affected by several sources of distortions

  16. Evolutionary Algorithms for Boolean Functions in Diverse Domains of Cryptography.

    Science.gov (United States)

    Picek, Stjepan; Carlet, Claude; Guilley, Sylvain; Miller, Julian F; Jakobovic, Domagoj

    2016-01-01

    The role of Boolean functions is prominent in several areas including cryptography, sequences, and coding theory. Therefore, various methods for the construction of Boolean functions with desired properties are of direct interest. New motivations on the role of Boolean functions in cryptography with attendant new properties have emerged over the years. There are still many combinations of design criteria left unexplored and in this matter evolutionary computation can play a distinct role. This article concentrates on two scenarios for the use of Boolean functions in cryptography. The first uses Boolean functions as the source of the nonlinearity in filter and combiner generators. Although relatively well explored using evolutionary algorithms, it still presents an interesting goal in terms of the practical sizes of Boolean functions. The second scenario appeared rather recently where the objective is to find Boolean functions that have various orders of the correlation immunity and minimal Hamming weight. In both these scenarios we see that evolutionary algorithms are able to find high-quality solutions where genetic programming performs the best.

  17. Free-space laser communication technologies III; Proceedings of the Meeting, Los Angeles, CA, Jan. 21, 22, 1991

    Science.gov (United States)

    Begley, David L. (Editor); Seery, Bernard D. (Editor)

    1991-01-01

    The present volume on free-space laser communication technologies discusses system analysis, performance, and applications, pointing, acquisition, and tracking in beam control, laboratory demonstration systems, and transmitter and critical component technologies. Attention is given to a space station laser communication transceiver, meeting intersatellite links mission requirements by an adequate optical terminal design, an optical approach to proximity-operations communications for Space Station Freedom, and optical space-to-ground link availability assessment and diversity requirements. Topics addressed include nonmechanical steering of laser beams by multiple aperture antennas, a free-space simulator for laser transmission, heterodyne acquisition and tracking in a free-space diode laser link, and laser terminal attitude determination via autonomous star tracking. Also discussed are stability considerations in relay lens design for optical communications, liquid crystals for lasercom applications, and narrowband optical interference filters.

  18. Free-space laser communication technologies; Proceedings of the Meeting, Los Angeles, CA, Jan. 11, 12, 1988

    Science.gov (United States)

    Koepf, Gerhard A.; Begley, David L.

    1988-01-01

    The present conference discusses topics in free-space laser communications, laser link characteristics, satellite laser communication systems, optoelectronic components for laser communications, and space laser subsystem technologies. Attention is given to Space Station-based deep-space communication experiments, the application of intersatellite links to operational satellite systems, high-power 0.87 micron channel substrate planar lasers for spaceborne communications, a ground experiment using a CO2 laser transceiver for free-space communications, studies of laser ranging to the TOPEX satellite, diffraction-limited tracking for space communications, and the compact implementation of a real-time, acoustooptic SAR processor.

  19. Testing the foundations of quantum mechanics

    CERN Document Server

    Gisin, Nicolas; CERN. Geneva

    1999-01-01

    Quantum mechanics is certainly one of the most fascinating field of physics. In recent years, the new field of "quantum information processing" based on the most fundamental aspect of quantum mechanics, like linearity and entanglement, even increased and its peculiarities. In this series of 4 lectures we shall present some of the issues and experiments that test quantum theory. Entanglement leads, on the one hand side, to the measurement problem, to the EPR paradox and to quantum nonlocality ( distant systems). We will derive the Bell inequality, present experimental results that provide huge evidence in favor of quantum nonlocality and discuss some loopholes that are still open. On the other side, entanglement offers many new possibilities for information processing. Indeed, it provides means to carry out tasks that are either impossible classically (like quantum cryptography and quantum teleportation) or that would require significantly more steps to perform on a classical computer (like searching a databas...

  20. An introduction to: the quantum world

    International Nuclear Information System (INIS)

    Le Bellac, M.

    2010-01-01

    Quantum physics has entered our daily life since it has allowed the invention of transistors and lasers. Now quantum engineering produces atomic clocks, semi-conductors, laser diodes and Led. This book is a popularization work on the quantum world, it introduces not only the basic principles but also explains its applications. 10 chapters compose this book each one illustrating a particular feature or an application as follows: chapter 1) the superposition principle, chapter 2) application to cryptography, chapter 3) Einstein's interpretation versus Bohr's, chapter 4) Heisenberg's inequalities and energy levels, chapters 5) and 6) the collective effects of quantum particles: applications to atom cooling and semi-conductors, chapter 7) relativity and quantum physics, chapter 8) quantum computers, chapter 9) quantum decoherence phenomenon and chapter 10) new interpretations of quantum physics. (A.C.)