Homodyne-detector-blinding attack in continuous-variable quantum key distribution

Abstract

We propose an efficient strategy to attack a continuous-variable quantum key distribution (CV-QKD) system, that we call homodyne detector blinding. This attack strategy takes advantage of a generic vulnerability of homodyne receivers: a bright light pulse sent on the signal port can lead to a saturation of the detector electronics. While detector saturation has already been proposed to attack CV-QKD, the attack we study in this paper has the additional advantage of not requiring an eavesdropper to be phase locked with the homodyne receiver. We show that under certain conditions, an attacker can use a simple laser, incoherent with the homodyne receiver, to generate bright pulses and bias the excess noise to arbitrary small values, fully comprising CV-QKD security. These results highlight the feasibility and the impact of the detector blinding attack. We finally discuss how to design countermeasures in order to protect against this attack.

Entropic uncertainty relations and the measurement range problem, with consequences for high-dimensional quantum key distribution

“…This issue has been discussed in [35,36], in the context of the Gaussian modulated coherent state protocol, a prepare-and-measure setting. They found that an eavesdropper can shift the mean of the distribution of results into the saturation regime, simultaneously lowering the variance of results, which causes Alice and Bob to overestimate the security of their key.…”

“…These degrees of freedom are, in principle, unbounded, while any practical detector for measuring them only has a finite range of detection, so a natural question has been whether the potential for the state to fall beyond the range of detection poses any serious consequences for the security of a protocol [13,19,[32][33][34][35][36]. Qi first noted the potential for a detection range loophole in time-frequency QKD [19], with Nunn et.…”

Unconditionally secured classical cryptography using quantum superposition and unitary transformation

“…Specifically the unconditional security of QKD is based on no-cloning theorem 4 , resulting from quantum superposition between paired conjugate (non-orthogonal) variables used for bases of a quantum key 5 . The unconditional security of QKD, however, is not guaranteed in practice due to the quantum loopholes based on imperfectness of a single photon detector 6 – 12 and/or a quantum channel 12 . The detection loophole with the channel loss affects all QKD protocols based on single photons 5 – 7 , entangled photon pairs 8 – 11 , and coherent continuous variables 12 .…”

Simultaneous two-way classical communication and measurement-device-independent quantum key distribution with coherent states

“…The gap between the ideal devices and the imperfect ones could lead to security loopholes. The side-channel attacks targeting the detector, such as saturation attacks [24,25] and blinding attacks [26] are the most popular eavesdropping strategies targeting imperfect detectors. Some known attacks have been investigated and eliminated, as shown in [27].…”