Greenberger-Horne-Zeilinger-Based Quantum Private Comparison Protocol With Bit-Flipping

By introducing a semi-honest third party (TP), this paper proposes a novel quantum private comparison (QPC) protocol using (n + 1)-qubit (n >= 2) Greenberger-Horne-Zeilinger (GHZ) states as information carriers. The parameter n not only determines the number of qubits contained in a GHZ state, but also determines the probability that TP can successfully steal the participants' data and the qubit efficiency. In the proposed protocol, any other quantum technologies (e.g., entanglement swapping and unitary operation) except necessary technologies such as preparing quantum states and quantum measurements are employed, which can reduce the need for quantum devices. The proposed protocol uses the keys generated by quantum key distribution and bit-flipping for privacy protection, and decoy photons for eavesdropping checking, making both external and internal attacks invalid. Specifically, for external attacks, several well-known attack means (e.g., the intercept-resend attack and the measurement-resend attack) are taken as examples to show that the attackers outside the protocol can not steal the participants' data successfully, in which the security proof of the protocol against the entanglement-measurement attack is provided. For internal attacks, it is shown that TP cannot steal the participants' data and the participants cannot steal each other's data. It is also shown that the existing attack means against QPC protocols are invalid for our protocol.