Practical Security Analysis of Reference Pulses for Continuous-Variable Quantum Key Distribution

Abstract

By manipulating the reference pulses amplitude, a security vulnerability is caused by self-reference continuous-variable quantum key distribution. In this paper, we formalize an attack strategy for reference pulses, showing that the proposed attack can compromise the practical security of CVQKD protocol. In this scheme, before the beam splitter attack, Eve intercepts the reference pulses emitted by Alice, using Bayesian algorithm to estimate phase shifts. Subsequently, other reference pulses are re-prepared and resubmitted to Bob. In simulations, Bayesian algorithm effectively estimates the phase drifts and has the high robustness to noise. Therefore, the eavesdropper can bias the excess noise due to the intercept-resend attack and the beam splitter attack. And Alice and Bob believe that their excess noise is below the null key threshold and can still share a secret key. Consequently, the proposed attack shows that its practical security can be compromised by transmitting the reference pulses in the continuous-variable quantum key distribution protocol.

Adaptive Modulation for Continuous-Variable Quantum Key Distribution With Real Local Oscillators Under Phase Attack

“…3b) systems under different phase attacks versus the transmission distance. We set the modulation variance of GM to 18.9 based on the experiment in [23], and 0.1 for 4-state. We assumed the phase noise of quantum channel is normally distributed with variance 0.0001 rad 2 , and that of Eve's phase attack is normally distributed with variance and (rad 2 ).…”

“…If eavesdroppers manipulate these reference pulses, the phase information carried by them becomes unreliable, and the phase compensation for coherent detection becomes imperfect. The imperfect phase compensation reduces the security of the CVQKD scheme [20,23].…”

“…The noise model of imperfect phase compensation for the traditional GM CV-QKD [18][19][20][21][22][23] is used in this paper to evaluate the practical security of the CV-QKD with real LOs. The actual phase compensation error is assumed to be zero-mean in the noise model of imperfect phase compensation.…”

“…The imperfection in phase compensation due to Eve's phase attack results in potential loopholes that may compromise the generation of secure key in CV-QKD systems. In [23], Bayesian algorithm is suggested as a method that can be utilized by Eve to estimate the phase drift of the reference pulse generated by CV-QKD based on GM or four-state protocols. In [20], a loopholes strategy that could be performed by Eve's phase attack is proposed for GM based CV-QKD, however, to the best of our knowledge, the above-mentioned method has not been studied and evaluated adequately for DM based CV-QKD protocol.…”

Feasibility assessment for practical continuous variable quantum key distribution over the satellite‐to‐Earth channel

“…Despite their intuitive appeal over LO schemes, attack strategies against LLO schemes do exist. In one such attack recently proposed, 69 Eve intercepts the reference pulse and estimates the phase drift using Bayesian algorithms. Consequently, the excess noise is biased to mask an intercept-resend attack and a beam-splitter attack.…”