Trojan-horse attacks threaten the security of practical quantum cryptography

A quantum key distribution system may be probed by an eavesdropper Eve by sending in bright light from the quantum channel and analyzing the back-reflections. We propose and experimentally demonstrate a setup for mounting such a Trojan-horse attack. We show it in operation against the quantum cryptosystem Clavis2 from ID~Quantique, as a proof-of-principle. With just a few back-reflected photons, Eve discerns Bob's secret basis choice, and thus the raw key bit in the Scarani-Ac\'in-Ribordy-Gisin 2004 protocol, with higher than 90% probability. This would clearly breach the security of the cryptosystem. Unfortunately in Clavis2 Eve's bright pulses have a side effect of causing high level of afterpulsing in Bob's single-photon detectors, resulting in a high quantum bit error rate that effectively protects this system from our attack. However, in a Clavis2-like system equipped with detectors with less-noisy but realistic characteristics, an attack strategy with positive leakage of the key would exist. We confirm this by a numerical simulation. Both the eavesdropping setup and strategy can be generalized to attack most of the current QKD systems, especially if they lack proper safeguards. We also propose countermeasures to prevent such attacks.Comment: 22 pages including appendix and references, 6+2 figure

The Point Spread Function Variations inside Wide-field Astonomical Images

The Point Spread Function (PSF) of the astronomical imaging system is usually approximated by a Gaussian or Moffat function. For simplification, the astronomical imaging system is considered to be time and space invariant. This means that invariable PSF within an exposed image is assumed. If real wide-field imaging systems are considered, this presumption is not fulfilled. In real systems, stronger optical aberrations are expected (especially coma) at greater distances from the center of the captured image. This impacts the efficiency of stellar astrometry and photometry algorithms, so it is necessary to know the PSF variation. In this paper, we perform the first step toward assigning PSF changes: we study the dependence of the Moffat function fitting parameters (FWHM and the atmospheric scattering coefficient ) on the position of a stellar object

Single-photon detectors for long distance quantum communications

Quantum communications and quantum cryptography are developing rapidly during the last decades caused partly by a fast progress in quantum computing. Quantum cryptography provides an unconditionally secure way of communicating whereas traditional classical cryptographic protocols are likely to be broken by super powerful quantum computers. In the past few years distances covered by quantum communications have increased by an order of magnitude. To provide a global coverage for the quantum networks, a satellite based quantum communications is the most promising solution. As an emerging field, QKD systems are still under evolution process. Despite outstanding security proven theoretically, it has loopholes caused by their implementations. To test QKD, find the possible loopholes and suggest ways to fix them, is a job of many scientific groups. In this thesis I start with presenting my work for a securing test of a commercial QKD system Clavis2. A Trojan-horse attack on Bob's apparatus was prepared by testing reflections and transmissions of all optical components in Bob's scheme. The attack was implemented and found to be unsuccessful at the tested wavelengths due to afterpulsing effect in Bob's single-photon detectors reacting to the bright light attack pulses. Three chapters of the thesis are dedicated to custom built single-photon detectors (SPDs) based on commercial Silicon avalanche photodiodes (APDs). Those detectors demonstrate parameters that altogether are not possible to find in commercially available SPDs, especially if combined with a very compact size. One of the in-lab-built SPDs was implemented in 143 km teleportation experiment, where a low dark count rate was crucial for the success of the experiment. The next generation SPD is already built, characterized and ready to be implemented. Another 4-channel SPD was built as a prototype for a quantum satellite SPD. It has light weight, low electrical power consumption, low dark count rate and decent other parameters. It was used in the airborne demonstration of QKD receiver payload experiment, when a secret key was successfully generated between a moving aircraft and a ground station. SPDs installed on a satellite have to be able to work in the harsh space environment during a mission life time. Space radiation dramatically increases dark count rate of APDs. The last project presented in the thesis committed to a radiation test of three types of APDs and one type of photo multiplier tube. The experiment included characterization of all SPDs before and after irradiation by four levels of proton radiation, equivalent to 3 months - 2 years duration in a 600 km low Earth orbit. Three methods for mitigating radiation damage were tested and found to be successful with perspective to use some of them on a quantum satellite to extent life time of SPDs. To summarize, this work makes a contribution to the development of SPDs for global quantum communications

Mitigating radiation damage of single photon detectors for space applications

Single-photon detectors in space must retain useful performance characteristics despite being bombarded with sub-atomic particles. Mitigating the effects of this space radiation is vital to enabling new space applications which require high-fidelity single-photon detection. To this end, we conducted proton radiation tests of various models of avalanche photodiodes (APDs) and one model of photomultiplier tube potentially suitable for satellite-based quantum communications. The samples were irradiated with 106 MeV protons at doses approximately equivalent to lifetimes of 0.6 , 6, 12 and 24 months in a low-Earth polar orbit. Although most detection properties were preserved, including efficiency, timing jitter and afterpulsing probability, all APD samples demonstrated significant increases in dark count rate (DCR) due to radiation-induced damage, many orders of magnitude higher than the 200 counts per second (cps) required for ground-to-satellite quantum communications. We then successfully demonstrated the mitigation of this DCR degradation through the use of deep cooling, to as low as -86 degrees C. This achieved DCR below the required 200 cps over the 24 months orbit duration. DCR was further reduced by thermal annealing at temperatures of +50 to +100 degrees C.Comment: The license has been corrected. Note that the license of v2 was incorrect and not valid. No other changes since v

Philosophical motives and spiritual imeratives of russian culture (the context of the axiology of creativity)

In the context of the ethical paradigm of spiritual education of young people, "inspired" by the moral philosophy of Russian culture, to substantiate a creative model in which tradition and innovation are combined, and the discursive field of which encompasses music, literature, and philosophy. Russian Russian traditional values are used to conceptualize the integral approach to the understanding and interpretation of the axiology of creativity, which is based on the dominance of Russian traditional values, and, first of all, substantiates the actual integration of "Russian leitmotives" into the modern multicultural environment.; secondly, the task is to increase the priorities in the Russian society and popularize the national spiritual and value imperatives that are important for the formation of a holistic cultural and historical worldview of the Russian youth, and to increase the level of their citizenship

Forms of manipulation in the discourse of social advertising

The article examines the specifics of using manipulation techniques in the discourse of social advertising. It is proposed to refer to manipulation the methods of distorting the linguistic picture of the addressee’s world with the help of the possibilities provided by linguistic mechanisms. The research material was 12,000 posters collected by the continuous sampling method from various media banks on the Internet. The authors refer to the most frequent manipulation techniques, objectively inherent in the discourse of social advertising, the distortions in the intensity of promoting ideas in the public consciousness, and the use of pseudo-rational arguments. The presence of these manipulation techniques is due to the fact that social advertising posters are produced most often by public funds that seek to promote only the ideas that are close to them. A situation arises when not those values that are more important for society are more actively promoted, but those that have material support from funds. The ideas promoted by different funds may conflict with each other and with the traditional values of the nation. In this “war of ideas”, two situations should be distinguished: 1) advertising encroaches on the values, which are traditionally recognized as important and promoted by state advertising (for example, for same-sex marriage, against vaccinations, etc.). 2) advertising raises questions regarding the settlement of relationships between people. Usually, such relationships have many options, so it is impossible to establish clear boundaries of a positive or negative attitude towards an object. Different funds interpret such situations in various ways in accordance with their ideology. Another active form of manipulation is the use of various forms of statistics that cannot be verified and which do not have any authoritative source behind them

Social pairing of Seychelles warblers under reduced constraints: MHC, neutral heterozygosity, and age

The prevalence and significance of precopulatory mate choice remains keenly debated. The major histocompatibility complex (MHC) plays a key role in vertebrate adaptive immunity, and variation at the MHC influences individual survival. Although MHC-dependent mate choice has been documented in certain species, many other studies find no such pattern. This may be, at least in part, because in natural systems constraints may reduce the choices available to individuals and prevent full expression of underlying preferences. We used translocations to previously unoccupied islands to experimentally reduce constraints on female social mate choice in the Seychelles warbler ( Acrocephalus sechellensis ), a species in which patterns of MHC-dependent extrapair paternity (EPP), but not social mate choice, have been observed. We find no evidence of MHC-dependent social mate choice in the new populations. Instead, we find that older males and males with more microsatellite heterozygosity are more likely to have successfully paired. Our data cannot resolve whether these patterns in pairing were due to male–male competition or female choice. However, our research does suggest that female Seychelles warblers do not choose social mates using MHC class I to increase fitness. It may also indicate that the MHC-dependent EPP observed in the source population is probably due to mechanisms other than female precopulatory mate choice based on MHC cues