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arXiv:1804.07003 · Cryptography

Synchronization in Quantum Key Distribution Systems

Anton Pavlovich Pljonkin, Konstantin E. Rumyantsev, Pradeep Kumar Singh

Published Oct 31, 2017• 32 citations
arXivHTMLPDF

Abstract

In the description of quantum key distribution systems, much attention is paid to the operation of quantum cryptography protocols. The main problem is the insufficient study of the synchronization process of quantum key distribution systems. This paper contains a general description of quantum cryptography principles. A two-line fiber-optic quantum key distribution system with phase coding of photon states in transceiver and coding station synchronization mode was examined. A quantum key distribution system was built on the basis of the scheme with automatic compensation of polarization mode distortions. Single-photon avalanche diodes were used as optical radiation detecting devices. It was estimated how the parameters used in quantum key distribution systems of optical detectors affect the detection of the time frame with attenuated optical pulse in synchronization mode with respect to its probabilistic and time-domain characteristics. A design method was given for the process that detects the time frame that includes an optical pulse during synchronization. This paper describes the main quantum communication channel attack methods by removing a portion of optical emission. This paper describes the developed synchronization algorithm that takes into account the time required to restore the photodetector’s operation state after the photon has been registered during synchronization. The computer simulation results of the developed synchronization algorithm were analyzed. The efficiency of the developed algorithm with respect to synchronization process protection from unauthorized gathering of optical emission is demonstrated herein.

DOI
10.3390/cryptography1030018

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In the description of quantum key distribution systems, much attention is paid to the operation of quantum cryptography protocols. The main problem is the insufficient study of the synchronization process of quantum key distribution systems. This paper contains a general description of quantum cryptography principles. A two-line fiber-optic quantum key distribution system with phase coding of photon states in transceiver and coding station synchronization mode was examined. A quantum key distribution system was built on the basis of the scheme with automatic compensation of polarization mode distortions. Single-photon avalanche diodes were used as optical radiation detecting devices. It was estimated how the parameters used in quantum key distribution systems of optical detectors affect the detection of the time frame with attenuated optical pulse in synchronization mode with respect to its probabilistic and time-domain characteristics. A design method was given for the process that detects the time frame that includes an optical pulse during synchronization. This paper describes the main quantum communication channel attack methods by removing a portion of optical emission. This paper describes the developed synchronization algorithm that takes into account the time required to restore the photodetector’s operation state after the photon has been registered during synchronization. The computer simulation results of the developed synchronization algorithm were analyzed. The efficiency of the developed algorithm with respect to synchronization process protection from unauthorized gathering of optical emission is demonstrated herein.
Purpose of the study: development and research of an algorithm for detecting an optical signal for synchronizing stations of a quantum key distribution system with increased protection against unauthorized access. Methods of research: probability distribution, statistical analysis, single-photon detection. Results: the importance of the time synchronization process, which is implemented through high-precision detection of an optical signal, is substantiated. An optical signal detection algorithm for a synchronization method with increased protection against unauthorized access is investigated. An improved algorithm for analyzing the time domain of synchronization signal propagation using avalanche photodetectors is proposed. It is shown that the proposed algorithm allows using avalanche photodetectors in the single photon counting mode. An analysis of the time characteristics of the developed synchronization algorithm is carried out and an analytical expression for calculating the time delay of detection is presented, which provides a sequential analysis of time windows taking into account the tunable recovery time of the photodetector. The analytical expression can be used for engineering calculations when designing a QKD system. The proposed algorithm significantly reduces the likelihood of unauthorized access to the synchronization process and allows determining the time parameters of the signal window with a given accuracy, which is critical for the subsequent operation of the quantum key distribution system. Scientific novelty: an algorithm for detecting an optical signal during synchronization is proposed, which is characterized by increased protection against unauthorized access. An analytical expression for engineering calculations of the delay of detection during synchronization is presented.
A review of the existing commercial quantum key distribution systems was conducted. The principle of operation of a fiber-optic quantum key distribution system with phase coding of photon states is described. The operation of the system in the mode of forming quantum keys is described. The synchronization process is analyzed, which consists in detecting a time interval with an optical pulse. The basic properties and parameters of auto-compensation quantum key distribution system are reviewed. The images of the current stand of the quantum-cryptographic network are given. The stand includes two stations of the quantum key distribution system with phase coding of photon states, two servers and data transmission channels. It is shown that the formation of a quantum key in the experiment is carried out at a rate of 500 bits per second. The length of the quantum communication channel in the experiment is 24 km. In this case, the quantum channel consists of a conventional single-mode optical fiber. Trends in the development of quantum key distribution systems, as well as trends in the development of protocols for quantum cryptography was conducted.
A typical structure of an auto-compensation system for quantum key distribution is given. The principle of operation of a fiber-optic system for the distribution of quantum keys with phase coding of photon states is described. The operation of the system in the synchronization mode and the formation of quantum keys was investigated. The process of detecting a time interval with an optical synchronization pulse is analyzed. The structural scheme of the experimental stand of the quantum-cryptographic network is given. Data are obtained that attest to the presence of a multiphoton signal during the transmission of sync pulses from the transceiver station to the coding and backward direction. The results of experimental studies are presented, which prove the existence of a vulnerability in the process of synchronization of the quantum key distribution system. It is shown that the use of a multiphoton optical pulse as a sync signal makes it possible for an attacker to unauthorized access to a quantum communication channel. The experimental results show that tapping a portion of the optical power from the quantum communication channel during the synchronization process allows an attacker to remain unnoticed while the quantum protocol is operating. Experimentally proved the possibility of introducing malfunctions into the operation of the quantum communication system at the stage of key formation, while remaining invisible for control means.
A typical structure of an auto-compensation system for quantum key distribution is given. The principle of operation of a fiber-optic system for the distribution of quantum keys with phase coding of photon states is described. The operation of the system in the synchronization mode and the formation of quantum keys was investigated. The process of detecting a time interval with an optical synchronization pulse is analyzed. The structural scheme of the experimental stand of the quantum-cryptographic network is given. Data are obtained that attest to the presence of a multiphoton signal during the transmission of sync pulses from the transceiver station to the coding and backward direction. The results of experimental studies are presented, which prove the existence of a vulnerability in the process of synchronization of the quantum key distribution system. It is shown that the use of a multiphoton optical pulse as a sync signal makes it possible for an attacker to unauthorized access to a quantum communication channel. The experimental results show that tapping a portion of the optical power from the quantum communication channel during the synchronization process allows an attacker to remain unnoticed while the quantum protocol is operating. Experimentally proved the possibility of introducing malfunctions into the operation of the quantum communication system at the stage of key formation, while remaining invisible for control means.
A two-pass fiber-optic quantum key distribution system with phase-encoded photon states in synchronization mode has been investigated. The possibility of applying the analytical expressions for the calculation of the correct detection probability of the signal time window at synchronization has been proved. A modernized algorithm of photon pulse detection, taking into account the dead time of the single-photon avalanche photodiode was proposed. The method of engineering an optical pulse detection process during the synchronization in a quantum key distribution system has been offered.
The object of this study is a two-pass fiber-optic quantum key distribution system (QKDS) with phase coding states of photons in synchronisation mode. The QKDS is based on a scheme with automatic compensation of polarisation distortions. We use single-photon avalanche photodiodes (SPAD) as optical radiation detection devices. We also evaluate the impact of parameters used in QKDS optical radiation detectors on probabilistic and time characteristics of the detected time interval with a weak optical pulse in sync. In this paper, we describe the methodology of the design process to detect a time interval with an optical pulse during synchronisation taking into account the features used in QKDS SPAD. The aim of our work is to evaluate the impact of QKDS changing hardware synchronisation settings on probabilistic and time characteristics of the detection time interval. We describe an algorithm that we have developed to synchronise a QKDS that considers the time to restore the operating state of a photon after registration during synchronisation. For evaluation, we report computer modelling results of the design process to detect a time interval according to the changing parameters applied in SPAD quantum key distribution systems.