Multi-party Quantum Private Comparison Protocol Based on Entanglement Swapping of Bell Entangled States

TL;DR

This paper introduces a multi-party quantum private comparison protocol based on entanglement swapping of Bell states, addressing security issues and extending the approach to multiple users for secure equality comparisons.

Contribution

It identifies security loopholes in existing protocols, proposes improvements using hash functions, and develops a generalized multi-party comparison protocol.

Findings

The protocol effectively prevents information leakage to the third party.

It ensures correctness and security through detailed validation.

The multi-party extension allows arbitrary pairwise comparisons among users.

Abstract

Recently, Liu W et al. proposed a two-party quantum private comparison (QPC) protocol using entanglement swapping of Bell entangled state (Commun. Theor. Phys. 57(2012)583-588). Subsequently, Liu W J et al. pointed out that in Liu W et al.'s protocol, the TP can extract the two users' secret inputs without being detected by launching the Bell-basis measurement attack, and suggested the corresponding improvement to mend this loophole (Commun. Theor. Phys. 62(2014)210-214). In this paper, we first point out the information leakage problem toward TP existing in both of the above two protocols, and then suggest the corresponding improvement by using the one-way hash function to encrypt the two users' secret inputs. We further put forward the three-party QPC protocol also based on entanglement swapping of Bell entangled state, and then validate its output correctness and its security in detail. Finally, we generalize the three-party QPC protocol into the multi-party case, which can accomplish arbitrary pair's comparison of equality among users within one execution.