Phase-reference-intensity attack on continuous-variable quantum key distribution with a local local oscillator

Abstract

In practical continuous-variable quantum key distribution system using local local oscillator (LLO CV-QKD), the phase noise related to coherent detection and phase-reference pulse intensity can be locally calibrated at the receiver side. Therefore, it can be regarded as trusted noise in order to obtain a higher secret key rate and transmission distance. However, security loopholes will be opened for the eavesdropper to launch attacks without appropriate countermeasures. To this end, we propose two practical phase-reference pulse intensity attack strategies, where Eve can reduce the trusted phase noise by manipulating the intensity of the phase-reference pulse, thereby hiding her attack on the signal pulse. The performance of the LLO CV-QKD system under these attacks has been analyzed. We show that precisely monitoring the intensity of the phase-reference pulse in real time is an essential countermeasure to prevent the proposed attacks. Moreover, an intensity-monitoring scheme for the phase-reference pulse is proposed to strengthen the security of the practical LLO CV-QKD system and make the trusted phase noise model more robust.