Study Of The Security Of Continuous-variable Quantum Key Distribution Systems With Local Oscillator Intensity Fluctuation

Quantum key distribution(QKD)is one of the most mature technologies in quantum information science.Due to its prospective application in the information security field,such a technology has drawn public attention for a long time.Theoretically,QKD enables legitimate parties to establish secret key unknown to eavesdroppers.The security is based on fundamental principles of quantum mechanics.In practical QKD systems,researchers found that by utilizing the drawbacks of practical devices,hackers can bypass the security architecture and implement attacks.Therefore,investigating the security issue of practical QKD systems is rather significant to the security of QKD.This paper is focused on the security of practical continuous-variable quantum key distribution(CVQKD)systems with local oscillator(LO)intensity fluctuation and theoretically discusses the following issues:1.Discuss how LO intensity fluctuation affects the security of practical CVQKD systems.Previous researches indicates that quantum hackers can alter the channel parameters estimation procedure by manipulating the LO intensity.Particularly,in cases when all LO pulses are attenuated,eavesdroppers can hide an intercept-and-resend attack.To perfect the research of this issue,this paper models the LO intensity in a general way and present the relationship between fluctuation parameters and channel parameters.The results indicate that when average LO intensity is equivalent to the initial calibrated LO intensity,as fluctuation parameter rises,total noises introduced by quantum channel would be overestimated and secret key rate would be underestimated.Underestimation of the secret key would remove the threats introduced by hackers automatically.2.Discuss the countermeasures for LO-intensity-related attacks.Investigate the commonness of current LO-intensity-related attacks and provide an unified countermeasure.On the one hand,control the fluctuation parameters to provide a secure scheme;on the other hand,discuss the possibility to apply the existing real-time shot-noise measurement technique to LO-intensity-related attacks.3.Discuss how LO intensity fluctuation affects the secure key rate of Gaussian protocols.In a successful and secure quantum communication process,when average LO intensity is equivalent to the initial calibrated LO intensity,the security of CVQKD systems can be guaranteed.However,this is based on sacrificing part of the secret key.Here,the secret key rate of different Gaussian protocols are discussed with LO intensity fluctuation.Research finds that,on the one hand,different protocols behaves completely different when LO fluctuates;on the other hand,compared with the choice of detection schemes,the choice of sources has a bigger influence on secret key rate.