Passive Faraday-mirror attack in a practical two-way quantum-key-distribution system

Abstract

The Faraday mirror (FM) plays a very important role in maintaining the stability of two-way plug-and-play quantum key distribution (QKD) systems. However, the practical FM is imperfect, which will not only introduce an additional quantum bit error rate (QBER) but also leave a loophole for Eve to spy the secret key. In this paper we propose a passive Faraday mirror attack in two-way QKD system based on the imperfection of FM. Our analysis shows that if the FM is imperfect, the dimension of Hilbert space spanned by the four states sent by Alice is three instead of two. Thus Eve can distinguish these states with a set of Positive Operator Valued Measure (POVM) operators belonging to three-dimension space, which will reduce the QBER induced by her attack. Furthermore, a relationship between the degree of the imperfection of FM and the transmittance of the practical QKD system is obtained. The results show that the probability that Eve loads her attack successfully depends on the degree of the imperfection of FM rapidly, but the QBER induced by Eve's attack changes slightly with the degree of the FM imperfection.

Experimental asymmetric plug-and-play measurement-device-independent quantum key distribution

“…First, the plug-and-play MDI-QKD is vulnerable to various source attacks [6,7,9] since the signal source is totally controlled by an untrusted server. By keeping a few assumptions including the single-mode assumption, the phase-randomization assumption, and the trust of the monitoring devices, a complete security analysis for plug-and-play MDI-QKD was derived in Ref.…”

“…The third approach is the measurement-device-independent QKD (MDI-QKD) [16], which removes all detection-related security loopholes. Such a loophole is arguably the most important issue identified in conventional QKD implementations [7][8][9][10]. Therefore, MDI-QKD is of great importance to promote the security of practical QKD systems.…”

“…In particular, a promising scheme is the plug-and-play MDI-QKD [18,33], which greatly reduces the experimental complexity of mode matching and referenceframe alignment. But, since the signal laser source and singlephoton detectors (SPDs) are in the charge of an untrusted server, plug-and-play MDI-QKD is vulnerable to source attacks [6,7,9]. Fortunately, with the security analysis reported in Ref.…”

“…Despite tremendous experimental effort being made in the field [3][4][5], an important problem in current QKD implementations is the gap between its theory and its practice [6][7][8][9][10]. To close this gap, three main approaches have been developed.…”

Risk Analysis of Trojan-Horse Attacks on Practical Quantum Key Distribution Systems

“…Such theory-practice deviations usually arise due to technical deficiencies and operational imperfections in the system hardware or firmware. The field of quantum hacking investigates such deviations [4][5][6] and many proof-of-principle quantum hacking attacks have been devised and performed on practical QKD systems in the last decade [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21].…”