LAUSR

Private comparison allows $n(n \ge 2)$ participants who do not trust each other to compare whether their secret data are the same, without leaking the secret data of their own. Quantum private comparison (QPC) uses quantum mechanics to accomplish the comparison. In this paper, we present a simple and effective method which can design QPC protocols based on multi-particle entangled states including the genuinely entangled five-qubit state, the generalized Brown state, the genuine six-qubit entangled state, etc. We take the Bell state and the genuinely entangled five-qubit state as examples, respectively, to present two QPC protocols, where a semi-honest third party who assists two participants in implementing the protocols is assumed. A key feature of our protocols is that quantum states are prepared by two participants rather than by the third party, which effectively prevents the third party from preparing fake quantum states, thus improving the security of the protocols. In addition, we use the entanglement properties of multi-particle entangled states and collaborative computing between participants for privacy protection, and we use QKD to ensure the security of the cooperative computing when two participants are in different locations. We show that the security of our protocols towards both outsider and insider attacks can be guaranteed.