Security Analysis On Practical QKD System

Quantum key distribution(QKD) is a mean of distributing unconditional secret key between two parties, it’s security guaranteed by quantum mechanics. Since 1984, Bennet and Brassard proposed the first the landmark QKD protocol(BB84 protocol), QKD become a hot research topic in the field of cryptography and depth studied by the majority of scholars. Then scholars propose many other classic QKD protocol, such as EPR protocol. Unconditional security of these QKD protocols in theory have been strictly proved, but practical QKD system exist non-ideal factors that does’ t meet the theoretical assumptions. In practical QKD system, the security assumptions are not completely satisfied and security loopholes exist. Real implementations of QKD may deviate from the ideal models in security proofs, such as laser with intensity fluctuation unable to meet the requirements of QKD protocol for single-photon source. Non ideal device in the actual QKD system may lead to potential security problems. Study the safety of the practical QKD system for promoting the application of QKD technology has important theoretical significance and practical significance. We first analyzed the security problems existing in the practical QKD system from the two aspects of physical module and post-processing, then analyzed the security of the practical QKD system with finite key. This paper mainly studies the following content:Based Lindeberg-Levy central limit theorem, this paper proposes a method of estimating the count rate and bit error rate of QKD system, our estimation method is more effective then Cai and Scarani’s method[21]. Then We using our estimation method given the lower bounds of the final key rate, and simulated the Secret key rate of the two methods of estimation. Simulation results show that the parameter estimation method to get the practical QKD system security code rate is higher than the literature[21].We analyzed the security of practical QKD system with finite key from two aspects of security definition in classic information and composability security definition in quantum information. Bennett’s security model assumes that the amount of Eve’s wiretapped information is know. However, we can only estimate the leaked information in practical QKD system. Therefore, we need to consider the effect of finite key. We consider the effect of finite key to analysis model, improved Bennett analysis theory and given the upper bound of leaked information of final key. In addition, we analyzed the security of practical system with finite key based on composability security.