Cryptanalysis of Multi-User Quantum Private Query Protocol

Recently, Tian et al. proposed a multi-user quantum private query protocol. The protocol realizes the function of n users querying the database at the same time, which can well protect the privacy of users and databases, and has high efficiency of implementation. Unfortunately, it has security vulnerability in the process of sending quantum sequences. Based on this vulnerability, we propose a man-in-the-middle attack on multi-user quantum private query protocol. Firstly, this paper reviews the multi-user quantum private query protocol. Secondly, the implementation steps of multi-user private query protocol are reviewed concisely. Finally, we pointed that in the protocol, Eve, the eavesdropper, can pretend to be Bob and the identity of the user to obtain the key of query data and steal the database information without being discovered. Through analysis, we find that man in the middle attack is feasible.