Reporters learned from the University of Science and Technology of China on the 7th that Han Zhengfu, Wang Shuang, Yin Zhenqiang, Chen Wei, a team of academicians Guo Guangcan of the university, found a potential security vulnerability in the modulation device at the sending end of the quantum key (QKD), and the quantum hacker attack experiment completed using the vulnerability showed that when the sending end of the QKD did not strictly protect against the vulnerability, the attacker might use it to obtain all key information. The two results of related research have been published online in the international academic journals "Optics" and "Applied Physics Review". In theory, QKD can generate Information theory secure keys between users. However, the non ideal characteristics of the actual device may not conform to the theoretical assumptions, so it can be used by eavesdroppers. Therefore, a comprehensive and in-depth analysis of the actual security of the QKD system, in order to design a more comprehensive and secure actual system, is an important link in promoting the practicality of QKD. On the basis of previous research, the research group proposed an attack idea of manipulating the working state of the core device of the QKD transmitter through external injection of photons, thereby stealing keys. The research team first proposed and analyzed the impact of photorefractive effect on QKD in commercial Lithium niobate devices, and then designed and verified the attack scheme against the BB84 protocol QKD system. The experimental results indicate that attackers can successfully carry out attacks by injecting 3nW of induced light from the outside. The team further designed a sender attack scheme for the measurement device independent QKD system: while measuring all the Quantum state sent by the sender, the attacker triggered the photorefractive effect of the Lithium niobate modulator at the sender by injecting induced light, thus hiding the disturbance caused by its measurement behavior. The research team used this scheme to complete the first quantum hacker attack experiment on a running measurement device independent QKD system, proving that eavesdroppers can obtain almost all keys without being detected. In response to the above security vulnerabilities and attack methods, the research team also proposed a system design concept and technical implementation plan that can effectively defend against this vulnerability, verifying that through good system design and optimized device usage, the actual security of the QKD system can be effectively improved. Researchers have stated that this achievement not only explores and analyzes potential vulnerabilities at the sending end and the threats they pose to the actual security of the system, but also proposes corresponding solutions, which helps trigger more in-depth and comprehensive thinking among researchers in the field on the actual security of QKD. It is of great significance for promoting the practicality and standardization of QKD. (New News Agency)