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arXiv:2107.07803 · Optics Letters

Measurement-device-independent quantum key distribution with insecure sources

Hua-Jian Ding, Xingyu Zhou, Chunhui Zhang, Jian Li, Qin Wang

Published Dec 15, 2021• 12 citations
arXivHTMLPDF

Abstract

Measurement-device-independent quantum key distribution (MDI-QKD) can remove all detection side channels but still makes additional assumptions on sources that can be compromised through uncharacterized side channels in practice. Here, we combine a recently proposed reference technique to prove the security of MDI-QKD against possible source imperfections and/or side channels. This requires some reference states and an upper bound on the parameter that describes the quality of the sources. With this formalism we investigate the asymptotic performance of single-photon sources, and the results show that the side channels have a great impact on the key rates.

DOI
10.1364/ol.447234

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Measurement-device-independent quantum key distribution (MDI-QKD) can remove all detection side channels but still makes additional assumptions on sources that can be compromised through uncharacterized side channels in practice. Here, we combine a recently proposed reference technique to prove the security of MDI-QKD against possible source imperfections and/or side channels. This requires some reference states and an upper bound on the parameter that describes the quality of the sources. With this formalism we investigate the asymptotic performance of single-photon sources, and the results show that the side channels have a great impact on the key rates.
Measurement-device-independent quantum key distribution (MDI-QKD) can remove all detection side-channels from quantum communication systems. The security proofs require, however, that certain assumptions on the sources are satisfied. This includes, for instance, the requirement that there is no information leakage from the transmitters of the senders, which unfortunately is very difficult to guarantee in practice. In this paper we relax this unrealistic assumption by presenting a general formalism to prove the security of MDI-QKD with leaky sources. With this formalism, we analyze the finite-key security of two prominent MDI-QKD schemes-a symmetric three-intensity decoy-state MDI-QKD protocol and a four-intensity decoy-state MDI-QKD protocol-and determine their robustness against information leakage from both the intensity modulator and the phase modulator of the transmitters. Our work shows that MDI-QKD is feasible within a reasonable time frame of signal transmission given that the sources are sufficiently isolated. Thus, it provides an essential reference for experimentalists to ensure the security of implementations of MDI-QKD in the presence of information leakage.
Measurement-device-independent quantum key distribution (MDI-QKD) is designed to be secure against any detector-side channel attacks. However, assumption of characterized sources in preparation is a demanding requirement and can not be fully satisfied in real-life implementations. Luckily, by utilizing the data of mismatched bases, the system can even generate secure keys with uncharacterized sources. Here, we give a framework on investigating the practical performance of an improved MDI-QKD with uncharacterized sources, where the three-intensity decoy-state method is employed and full parameter optimizations are applied. Simulation results show that the improved method can significantly enhance the performance compared with the original MDI-QKD with uncharacterized sources.
Measurement-device-independent quantum key distribution (MDI-QKD) can be immune to all detector side-channel attacks and guarantee the information-theoretical security even with uncharacterized single photon detectors. MDI-QKD has been demonstrated in both laboratories and field-tests by using attenuated lasers combined with the decoy-state technique. However, it is a critical assumption that the sources used by legitimate participants are trusted in MDI-QKD. Hence, it is possible that a potential security risk exists. Here we propose a new scheme of polarization-encoding-based MDI-QKD with a single untrusted source, by which the complexity of the synchronization system can be reduced and the success rate of the Bell-state measurement can be improved. Meanwhile, the decoy-state method is employed to avoid the security issues introduced by a non-ideal single photon source. We also derive a security analysis of the proposed system. In addition, it seems to be a promising candidate for the implementation for QKD network in the near future.
Abstract Reference-frame-independent measurement-device-independent quantum key distribution (RFI-MDI-QKD) can remove all potential detector side-channel attacks and the requirement of real-time alignment of reference frames. However, all previous RFI-MDI-QKD implementations assume the perfect state preparation in sources, which is impractical and may lead to security loopholes. Here, we propose an RFI-MDI-QKD protocol which is robust against state preparation flaws. Comparing to the conventional six-state RFI-MDI-QKD, our scheme can be realized with only four flawed states, which improves the practical security of RFI-MDI-QKD and simplifies the experimental implementation. In addition, simulation results demonstrate that source flaws in Z basis have adverse effect on the performance of RFI-MDI-QKD while the source flaws in X and Y bases have almost no effect. We hope that this work could provide a valuable reference for practical implementations of RFI-MDI-QKD.
Measurement-device-independent quantum key distribution (MDI-QKD), which is immune to all detector side-channel attacks, is the most promising solution to the security issues in practical quantum key distribution systems. Although several experimental demonstrations of MDI-QKD have been reported, they all make one crucial but not yet verified assumption, that is, there are no flaws in state preparation. Such an assumption is unrealistic and security loopholes remain in the source. Here we present a MDI-QKD experiment with the modulation error taken into consideration. By applying the loss-tolerant security proof by Tamaki et al. [Phys. Rev. A 90, 052314 (2014)], we distribute secure keys over fiber links up to 40 km with imperfect sources, which would not have been possible under previous security proofs. By simultaneously closing loopholes at the detectors and a critical loophole---modulation error in the source, our work shows the feasibility of secure QKD with practical imperfect devices.
The security of practical quantum key distribution (QKD) systems is fundamentally constrained by vulnerabilities of single-photon detectors. Measurement-device-independent quantum key distribution (MDI-QKD) was proposed to remove this limitation by allowing all measurements to be performed by a completely untrusted party, under the assumption that the measurement node can be treated as adversarial but does not compromise the security guarantees of the protocol. Here we show that this assumption is insufficient under realistic adversarial control of the measurement device. We present an attack in which an adversary exploits active control of the measurement node (Charlie) to obtain significant information about the secret key. The attack enables recovery of up to 70\% of the sifted key while introducing only 5.6\% quantum bit error rate. Unlike previously reported attacks targeting specific implementations of MDI-QKD, our results demonstrate a limitation of the standard security model underlying the protocol. These findings indicate that additional constraints on the measurement-device independence assumption, or refined security analyses incorporating stronger adversarial capabilities, are required to ensure the security of MDI-QKD in realistic scenarios.