Cryptanalysis and improvement of a semi-quantum private comparison protocol based on Bell states

Abstract

Semi-quantum private comparison (SQPC) allows two participants with limited quantum ability to securely compare the equality of their secrets with the help of a semi-dishonest third party (TP). Recently, Jiang (Quantum Inf Process 19(6): 180, 2020) proposed a SQPC protocol based on Bell states and claimed it is secure. In this paper, we present two types of attack on Jiang’s SQPC protocol. In the first type of attack, an outside eavesdropper can make participants accept a wrong result. In the second type of attack, a malicious participant not only can make the other participant accept an incorrect result, but also can learn the secret of the honest participant. Neither type of attack is possible to be detected. In addition, we propose an improved SQPC protocol that can resist these two types of attack.