Homodyne-detector-blinding attack in continuous-variable quantum key distribution
This work addresses a critical security vulnerability in CV-QKD systems, which is incremental as it builds on prior detector saturation attacks but removes the need for phase locking.
The authors proposed a homodyne detector blinding attack on continuous-variable quantum key distribution (CV-QKD) systems, exploiting detector saturation vulnerabilities to bias excess noise to arbitrarily low values and fully compromise security, demonstrating feasibility with a simple, incoherent laser.
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.