Polarization attack on continuous-variable quantum key distribution

TL;DR

This paper reveals a polarization-based hacking method that allows an eavesdropper to manipulate the shot-noise unit in continuous-variable quantum key distribution, compromising its security by exploiting polarization compensation limitations.

Contribution

It introduces a novel quantum hacking technique targeting the practical SNU control in CV-QKD systems, highlighting a new security vulnerability.

Findings

Practical SNU can be controlled by an eavesdropper.

Manipulating SNU affects excess noise and key rate.

Experimental validation confirms the attack's effectiveness.

Abstract

The shot-noise unit (SNU) is a crucial factor for the practical security of a continuous-variable quantum key distribution system. In the most widely used experimental scheme, the SNU should be calibrated first and acts as a constant during the key distribution. However, the SNU of a practical system is dependent on the various parameters of the local oscillator, which can be controlled by the eavesdropper in the open channel. In this paper, we report a quantum hacking method to control the practical SNU by using the limited compensation rate of the polarization compensation. Since the compensation is only based on of the polarization measurement results of part of local oscillator pulses, the polarization of other unmeasured pulses may not be compensated correctly, which can be utilized by the eavesdropper to control the practical SNU. The simulation and experiment results indicate that the practical SNU can be controlled by the eavesdropper. Thus, the eavesdropper can use the fact that the practical SNU is no longer equals to the calibrated one to control the excess noise and final key rate.