Quantum key distribution (QKD) systems are open systems. Thus, an eavesdropper can actively influence the elements of the system through the communication line, altering their regular operation. One known attack is an attack with detector blinding. With such an attack, the eavesdropper can obtain the entire key and remain undetectable. The paper proposes a fundamentally new method of detecting and protecting quantum cryptography systems with phase coding against the attack with avalanche detector blinding. The proposed method is based on diverting a part of the input signal in the receiving terminal to bypass the interferometer and deliver it to the same avalanche detectors. Measuring the detector response in different time windows, both for the bypassed signal and the normal operation range, one can effectively identify the ongoing detector blinding attack. The method does not require radical changes in existing quantum cryptography systems and is quite universal, since it can be used for any phase-coded quantum key distribution protocol. The method provides a fundamental strategy of detecting and protecting against the attack at the level of the quantum key distribution protocol, and not at the level of technical ‘patches’.

量子密钥分发 (QKD) 系统是开放系统。因此，窃听者可以通过通信线路主动影响系统的元素，改变它们的正常运行。一种已知的攻击是检测器致盲攻击。通过这种攻击，窃听者可以获得整个密钥并且无法被检测到。本文提出了一种全新的检测和保护相位编码量子密码系统的方法，以抵御雪崩检测器致盲的攻击。所提出的方法是基于将接收端的一部分输入信号转向绕过干涉仪并将其传送到相同的雪崩检测器。测量不同时间窗口的检测器响应，包括旁路信号和正常工作范围，一个可以有效识别正在进行的检测器致盲攻击。该方法不需要对现有的量子密码系统进行根本性的改变，并且非常通用，因为它可以用于任何相位编码的量子密钥分发协议。该方法提供了一种在量子密钥分发协议级别而非技术“补丁”级别检测和防止攻击的基本策略。