量子密钥分发系统的实际安全性

The Practical Security of Quantum Key Distribution System

量子密钥分发利用量子力学原理实现通信双方之间无条件安全的密钥传输而不被未经许可的第三方所窃听。目前,单光子QKD协议,纠缠光子对QKD协议,连续变量QKD协议等在理想的光源、信道、探测模型假设下已经被证明具有无条件安全性。然而,实际QKD系统所采用的非理想实际物理器件往往不完全符合理论安全性分析中的模型假设,这将导致比较严重的安全漏洞,从而降低实际QKD系统的安全性。为了抵御实际QKD系统非理想器件所引入的安全漏洞,可以从软件上改进QKD理论安全性分析(将实际QKD系统非理想特性纳入到安全性分析理论中),或从硬件上改进实际QKD系统(增加监控模块以抵御实际QKD系统安全漏洞)。对实际QKD系统光源、信道及探测端的安全漏洞进行了全面总结并给出针对各个安全隐患的抵御措施。

Quantum key distribution （QKD） enables to share a secret key between two parties in the pres- ence of an eavesdropper （Eve）. The single-photon, entanglement-based and continuous variable QKD pro- tocols have proved to be unconditionally secure under ideal （source, channel, detection） assumptions. In practical QKD systems, the security assumptions are not completely satisfactory so that security loopholes exist. The unconditional security of practical QKD systems will be compromised if these loopholes are not included in general security analysis or no counter measures are made. To fight against the security loop- holes due to the imperfect physical devices in practical QKD systems, the theoretical security analysis in software, can be impraved which includes all the loopholes in QKD systems ; or the physical implementation of practical QKD system in hardware can be improved, where monitoring devices should be added to moni- tor the practical security loopholes. In this paper, the practical loopholes in QKD source, channel and de- tection are reviewed in detail, while counter-measures are given to fight against the loopholes.