光子数分束攻击对星地量子密钥分配系统安全的影响

由于仪器设备性能的不完美和信道传输损耗的存在,光子数分束(PNS)攻击对采用弱相干脉冲(WCP)光源的量子密钥分配(QKD)系统的安全性构成重大威胁.以基于WCP光源的星地QKD系统为研究对象,推导了在PNS攻击者采用最佳窃听策略进行窃听时,保证密钥绝对安全的最大天顶角和可采用的平均光子数之间的关系.理论分析和计算结果表明,星地QKD系统的最大安全传输天顶角和可使用的平均光子数等重要系统参数的取值上限均受PNS攻击的限制,最终系统的密钥交换速率和系统容量受到限制.对星地QKD系统的传输容量来说,天顶角和平均光子数是一对矛盾的影响因素.提供了一种对实际星地QKD系统的天顶角和平均光子数参数进行估算的方法.

Effects of Photon-Number-Splitting Attacks on the Security of Satellite-to-Ground Quantum Key Distribution Systems

The security of practical quantum key distribution (QKD) systems based on weak coherent pulse (WCP)sources is imperiled by photon number splitting (PNS) attacks due to imperfectness of devices and channel loss. The relation between the zenith angle and the mean photon number for security of a satellite-to-ground QKD system based on the WCP source against PNS attacks which operates with the optimal eavesdropping strategy is provided. The theoretical and calculation results shows the upper limits of key parameters for satellite-to-ground QKD systems, such as the zenith angle and the mean photon number, are limited by PNS attacks, and eventually the key exchange rate and the capacity of QKD systems are limited as well. The zenith angle and the mean photon number have an incompatible effect on the capacity of a satellite-to-ground QKD system. At the same time a method of parameter estimation of the zenith angle and the mean photon number for security of practical satellite-to-ground QKD systems against PNS attacks is provided.