Feasible attack on detector-device-independent quantum key distribution

Kejin Wei,Hongwei Liu,Yuefeng Ji,Yongmei Sun,Xiuqing Yang,Jinghua Xiao,Haiqiang Ma,Yong Zhang

doi:10.1038/s41598-017-00531-y

Abstract

Recently, to bridge the gap between security of Measurement-device-independent quantum key distribution (MDI-QKD) and a high key rate, a novel protocol, the so-called detector-device-independent QKD (DDI-QKD), has been independently proposed by several groups and has attracted great interest. A higher key rate is obtained, since a single photon bell state measurement (BSM) setup is applied to DDI-QKD. Subsequently, Qi has proposed two attacks for this protocol. However, the first attack, in which Bob’s BSM setup is assumed to be completely a “black box”, is easily prevented by using some additional monitoring devices or by specifically characterizing the BSM. The second attack, which combines the blinding attack and the detector wavelength-dependent efficiency, is not explicitly discussed, and its feasibility is not experimentally confirmed. Here, we show that the second attack is not technically viable because of an intrinsically wavelength-dependent property of a realistic beam splitter, which is an essential component in DDI-QKD. Moreover, we propose a feasible attack that combines a well-known attack—detector blinding attack with intrinsic imperfections of single-photon detectors. The experimental measurement and proof-of-principle test results confirm that our attack can allow Eve to get a copy of quantum keys without being detected and that it is feasible with current technology.

Highlights

Quantum key distribution (QKD) enables two legitimate parties, usually called Alice and Bob, to share a private key through a quantum channel, which is possible in the presence of an eavesdropper, Eve[1, 2]
We show that the wavelength-dependent attack in ref. 36 is not technically viable because of the harm caused by an intrinsically wavelength-dependent property of a realistic beam splitter, which is an essential component in detector-deviceindependent QKD (DDI-QKD)
Our experimental measurement and proof-of-principle test results confirm that our attack can allow Eve to get a copy of a quantum key without being detected and that it is feasible with current technology

Summary

Introduction

Quantum key distribution (QKD) enables two legitimate parties, usually called Alice and Bob, to share a private key through a quantum channel, which is possible in the presence of an eavesdropper, Eve[1, 2]. Real-life implementations of QKD inevitably contain certain imperfections leaving some vulnerable loopholes (the so-called side channels) Such loopholes have been exploited by Eve and have led to various subtle attacks for real-life QKD systems[5–16]. To bridge the gap between security of MDI-QKD and a high key rate, a novel protocol, the so-called detector-device-independent QKD (DDI-QKD)[31], has been independently proposed by several groups and has www.nature.com/scientificreports/. If detectors in the BSM have different wavelength-dependent efficiencies, Eve exploits such an imperfection to cover unusual double-click rate s caused by her attack. To avoid an unusual double-click rate, different from the wavelength-dependent attack, we utilize another imperfection that two practically blinded detectors respond differently to the same blinding power. We remark that our attack is not against the wavelength-dependent attack; strictly speaking, we propose an alternative solution to the problem of double clicks in the wavelength-dependent attack and experimentally confirm its feasibility

Methods

Results

Conclusion