An efficient protocol for the quantum private comparison of equality with a four-qubit cluster state

In this paper, we further research the quantum private comparison protocol with the semi-honest participant, in which two parties can test the equality of their information without revealing the content to anyone. Considering both the success of protocol and the security of information, we first give a reasonable and significant description about the semi-honest model in quantum secure communications. Moreover, based on the feature of four-qubit cluster state which has the great robust against decoherence, we propose a new protocol for the quantum private comparison. Our protocol ingeniously utilizes the special symmetry of the four-qubit cluster state to enhance the efficiency of comparison. This new protocol is secure. The participants only know the result of comparison; cannot know each other's private information. TP cannot learn anything about the private information, even about the comparison result and the length of secret inputs.