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Voprosy kiberbezopasnosti

AUTONOMOUS SYNCHRONIZATION ALGORITHM FOR MDI-QKD

Anton Pavlovich Pljonkin

Published Jan 1, 2026• 0 citations
Publisher

Abstract

Purpose of the study: develop and evaluate an algorithm for synchronizing stations in a quantum key distribution system with an untrusted intermediate node. Methods of research: probability distribution, statistical analysis, Gaussian distribution. Results: the importance of high-precision synchronization is substantiated, an autonomous optical signal search algorithm is proposed and analyzed, and simulation results are presented. The issue of autonomous synchronization of two remote stations in a quantum key distribution system is considered. The station connection scheme is a topology with an untrusted intermediate node. An algorithm for synchronizing stations with an untrusted intermediate node is proposed, which does not require an additional optical communication channel. A unique feature of the algorithm is that the stations independently determine the distance to the beam splitter in the untrusted node with an accuracy of tens of picoseconds. Simulation modeling of the developed algorithm is conducted, and the results are presented. This paper describes the operating principle of the MDI quantum key distribution protocol within a mixed-topology quantum network and proposes a scheme for interaction between several legitimate users of the quantum network and a single untrusted node. Scientific novelty: an algorithm for synchronizing optical signals in quantum networks for MDI-QKD is proposed, characterized by its autonomous implementation. Simulation results for the algorithm are presented, and data are obtained that improve the efficiency of engineering calculations when designing a synchronization system.

DOI
10.21681/2311-3456-2026-2-119-128

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Purpose of the study: develop and evaluate an algorithm for synchronizing stations in a quantum key distribution system with an untrusted intermediate node. Methods of research: probability distribution, statistical analysis, Gaussian distribution. Results: the importance of high-precision synchronization is substantiated, an autonomous optical signal search algorithm is proposed and analyzed, and simulation results are presented. The issue of autonomous synchronization of two remote stations in a quantum key distribution system is considered. The station connection scheme is a topology with an untrusted intermediate node. An algorithm for synchronizing stations with an untrusted intermediate node is proposed, which does not require an additional optical communication channel. A unique feature of the algorithm is that the stations independently determine the distance to the beam splitter in the untrusted node with an accuracy of tens of picoseconds. Simulation modeling of the developed algorithm is conducted, and the results are presented. This paper describes the operating principle of the MDI quantum key distribution protocol within a mixed-topology quantum network and proposes a scheme for interaction between several legitimate users of the quantum network and a single untrusted node. Scientific novelty: an algorithm for synchronizing optical signals in quantum networks for MDI-QKD is proposed, characterized by its autonomous implementation. Simulation results for the algorithm are presented, and data are obtained that improve the efficiency of engineering calculations when designing a synchronization system.
Measurement-device-independent quantum key distribution (MDI-QKD) eliminates detector side-channel attacks by relocating all measurements to an untrusted intermediate node. However, its practical implementation critically relies on picosecond-level temporal synchronization between spatially separated users. In this work, we present a physically motivated autonomous synchronization algorithm for fiber-based MDI-QKD networks that does not require auxiliary optical channels or shared clock references. The method exploits round-trip optical pulse propagation and statistical signal detection in the presence of Gaussian noise. We derive analytical expressions for false-alarm probabilities, quantify detection reliability, and demonstrate through numerical modeling that synchronization accuracy better than 10~ps is achievable for channel lengths up to 100~km with realistic optical power levels. The proposed approach improves the scalability and robustness of MDI-QKD architectures and is directly applicable to metropolitan and backbone quantum networks.
Measurement-device-independent quantum key distribution (MDI-QKD) eliminates detector side-channel attacks by relocating all measurements to an untrusted intermediate node. However, its practical implementation critically relies on picosecond-level temporal synchronization between spatially separated users. In this work, we present a physically motivated autonomous synchronization algorithm for fiber-based MDI-QKD networks that does not require auxiliary optical channels or shared clock references. The method exploits round-trip optical pulse propagation and statistical signal detection in the presence of Gaussian noise. We derive analytical expressions for false-alarm probabilities, quantify detection reliability, and demonstrate through numerical modeling that synchronization accuracy better than 10 ps is achievable for channel lengths up to 100 km with realistic optical power levels. The proposed approach improves the scalability and robustness of MDI-QKD architectures and is directly applicable to metropolitan and backbone quantum networks.
Measurement-device-independent quantum key distribution (MDI-QKD) eliminates detector side-channel attacks by relocating all measurements to an untrusted intermediate node. However, its practical implementation critically relies on picosecond-level temporal synchronization between spatially separated users. In this work, we present a physically motivated autonomous synchronization algorithm for fiber-based MDI-QKD networks that does not require auxiliary optical channels or shared clock references. The method exploits round-trip optical pulse propagation and statistical signal detection in the presence of Gaussian noise. We derive analytical expressions for false-alarm probabilities, quantify detection reliability, and demonstrate through numerical modeling that a scanning resolution of 10 ps is achievable for channel lengths of up to 100 km with realistic optical power levels. The actual timing accuracy is limited by detector, source, and electronic jitter and is not quantified in this work. The proposed approach improves the scalability and robustness of MDI-QKD architectures and is directly applicable to metropolitan and backbone quantum networks.
Measurement-device-independent quantum key distribution (MDI-QKD) eliminates detector side-channel attacks by relocating all measurements to an untrusted intermediate node. However, its practical implementation critically relies on picosecond-level temporal synchronization between spatially separated users. In this work, we present a physically motivated autonomous synchronization algorithm for fiber-based MDI-QKD networks that does not require auxiliary optical channels or shared clock references. The method exploits round-trip optical pulse propagation and statistical signal detection in the presence of Gaussian noise. We derive analytical expressions for false-alarm probabilities, quantify detection reliability, and demonstrate through numerical modeling that synchronization accuracy better than 10 ps is achievable for channel lengths up to 100 km with realistic optical power levels. The proposed approach improves the scalability and robustness of MDI-QKD architectures and is directly applicable to metropolitan and backbone quantum networks.
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.
Quantum key distribution (QKD) can serve large numbers of users with unconditional secure communication, in which measurement-device-independent (MDI) QKD protocol can conveniently enhance realistic security by eliminating all detector side channels. In multi-user scenarios, MDI-QKD networks should meet the requirements of reliability and robustness. Around the issues, we complete a series of work on performance improvement, low-cost deployment, and robust networking. First is to answer how to change the trusted node to the untrusted node with low cost, here we propose and demonstrate an MDIQKD which is compatible with phase encoding BB84 networks, allowing for economical deployment of MDI-QKD networks and reconciliation between high key rate and high realistic security in the same network. Then we make the MDI networks more robust. We design an MDI-QKD networking scheme for multi-user access where more than two users can generate keys synchronously regardless of aligning reference frames and compensating channel disturbance on polarization. Third, we find a general method to distil secure keys from quantum discord, which is different to the previous entanglement-based frameworks of MDI-QKD, allowing imperfect preparation and measurement of quantum states. The series of work can help the practical application of MDI-QKD networks, and promote the development of quantum networks.