Quantum Private Comparison Based on GHZ-type States

In this paper, an efficient quantum private comparison (QPC) protocol based on GHZ-type states is proposed. Two participants can compare the equality of two classical bits in each comparison, which could greatly reduce comparison times and increase efficiency. A semi-honest third-party (TP) is involved in assisting the participants to compare their secrets. TP may misbehave on her own, but she is not allowed to conspire with any participants. Besides, the proposed protocol needs Hadamard operation as well as single-particle measurements and Bell measurements, which are easy to implement with current technologies. Finally, the analysis shows the proposed protocol is correct and it can resist various attacks including outside attacks and dishonest participant attacks.