Cryptanalysis of the Quantum Private Comparison Protocol Based on the Entanglement Swapping Between Three-Particle W-Class State and Bell State

Abstract

Recently, Li et al. (Int. J. Theor. Phys. 55, 1710–1718, 2016) proposed a Quantum Private Comparison (QPC) protocol based on the Entanglement Swapping Between Three-Particle W-Class State and Bell State. Two parties can check whether their secret information is equal or not with the help of the semi-honest third party (TP). However in this paper, we will point out this kind of semi-honest TP is unreasonable. If we relax the constraint of the semi-honest TP, by using the fake signal attack, TP can know the whole secret information illegally. At last, we give our improvement, which can make this protocol more secure.