Abstract
Quantum key distribution (QKD) protocol has been proved to provide unconditionally secure key between two remote legitimate users in theory. Key distribution signals are transmitted in a quantum channel which is established by the calibration process to meet the requirement of high count rate and low error rate. All QKD security proofs implicitly assume that the quantum channel has been established securely. However, the eavesdropper may attack the calibration process to break the security assumption of QKD and provide precondition to steal information about the final key successfully. In this paper, we reveal the security risk of the calibration process of a passive-basis-choice BB84 QKD system by launching a quantum man-in-the-middle attack which intercepts all calibration signals and resends faked ones. Large temporal bit-dependent or basis-dependent detector efficiency mismatch can be induced. Then we propose a basis-dependent detector efficiency mismatch (BEM) based faked states attack on a single photon BB84 QKD to stress the threat of BEM. Moreover, the security of single photon QKD systems with BEM is studied simply and intuitively. Two effective countermeasures are suggested to remove the general security risk of the calibration process.
Highlights
Comparing with traditional communication protocols, quantum key distribution (QKD) protocol has been proven to have unconditional security to distribute key between two remote parties, known as Alice and Bob, with the assumption that all devices are perfect[1,2,3]
The security of practical Quantum key distribution (QKD) systems is closely related to the calibration process, which is needed to be studied to assure no loophole is induced before key distribution
Jain et al.[29], we propose a quantum man-in-the-middle attack strategy on the activation timing calibration process and experimentally reveal the security risk of the independent scanned activation timing on a passive-basis-choice BB84 QKD system by separating the efficiency curves of detectors in two bases, i.e., basis dependent detector efficiency mismatch (BEM)
Summary
Comparing with traditional communication protocols, quantum key distribution (QKD) protocol has been proven to have unconditional security to distribute key between two remote parties, known as Alice and Bob, with the assumption that all devices are perfect[1,2,3]. The security of practical QKD systems is closely related to the calibration process, which is needed to be studied to assure no loophole is induced before key distribution. Almost all QKD systems need to calibrate the activation timing of gated-mode detectors before key distribution. QKD systems with multiple detectors always scan the activation timing of gated-mode detectors independently to reduce the detector efficiency mismatch occurred naturally in time frame[17,29,31]. This design works well without Eve and a large detector efficiency mismatch occurs with the probability of only 4 %16. This convenient design may be utilized by Eve to induce large detector efficiency mismatch in the calibration process
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