Practical Security Analyses For Quantum Key Distribution Protocols

Quantum key distribution(QKD)is one of the most established quantum-information technologies to date.Its security is based on fundamental quantum theory and has been proved to be unconditional secure theoretically.After 30 years'study since its initial proposal,QKD has been widely studied in both theoretical and experimental research.The QKD protocol has been proven to be unconditionally secure under ideal conditions.However,the imperfections of practical devices may pose serious threats of a security breach.Hence,it's very important for us to analyze the security of QKD protocols in practical quantum system and improve the secure key rate and transmission distance.It is also urgent to propose a new QKD protocol which is more suitable for real quantum system and can be transmitted over long distance.This dissertation focuses on the above issues,the main research content is as follows:In this dissertation,we established the passive decoy state Measurement device independent(MDI)QKD protocol model with polarization encoding mode.Not only all the attacks on detectors can be removed,but also the side channels attacks on sources can be avoided,which may be generated by active modulation of source intensities.We analyzed the practical security of this protocol,estimated the tight bound of eavesdropping information,and improves the security key rate and transmission distance of the protocol.Moreover,in order to fit for the demand of practical application,the effects of the intensity fluctuation and the finite-size pulses on the protocol are studied.In this dissertation,we studied the security analysis of Round-robin differ-ential phase shift(RRDPS)QKD protocol in practical system,proposed passive decoy state RRDPS QKD protocol model.This protocol provides a secure way to exchange information without monitoring conventional disturbances and still maintains a high tolerance of noise and long transmission distance.Meanwhile,it can also exclude the source side channel attacks caused by active modulation of source intensities.Moreover,since the phase error rate of RRDPS QKD pro-tocol is a fixed value,the estimated value of the single photon counting rate and the security key rate formula are given in this paper by using the passive decoy state method.The secure key rate and transmission distance of our protocol can have a performance improvement to the protocol with the active decoy state method and the original RRDPS protocol without decoy states.In this dissertation,we proposed and analyzed the security of six-coherent-state protocol based on non-phase-randomized coherent states.We showed that our protocol offers significant advantages in both secret key rate and trans-mission distance over existing coherent-state QKD protocols.We applied the hierarchy semi-definite programming method to analyze the security of QKD protocol in this paper.Our analysis requires fewer assumptions on both the quantum state preparation and measurement processes as it relies solely on the overlaps of the code states as well as the observed statistics.Simulating with a realistic experimental model,our protocol can tolerate a total loss of up to 38 dB,which is much higher than previous non-phase-randomized coherent state QKD protocol.In addition to the improved key rates,it's not necessary for six-coherent-state QKD protocol to randomize the phase of their quantum signals,which is easy to implement.In this dissertation,we proposed a covert QKD protocol with decoy-state method to solve the key regeneration problem in covert quantum communica-tion,and the secure key rate and covertness of the covert decoy-state QKD pro-tocol are proved.The protocol can not only enable the two parties to generate secure keys,but also ensure the covertness of the communication.In addition,in order to make the protocol more practical,the influence of the finite number pulses on the protocol in the actual system is analyzed.Compared with the conventional covert decoy-state QKD protocol,the proposed covert decoystate QKD protocol has higher security key rate and longer security transmission distance.