Entanglement-based quantum private comparison protocol with bit-flipping

Quantum private comparison (QPC), whose security is based on the laws of quantum mechanics, allows at least two participants who do not trust each other to compare whether their secret data are the same while maintaining data privacy. Here, by introducing a semi-honest third party, we propose a novel QPC protocol using (n+1)-qubit (n\ge2) 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 the third party can successfully steal participants' data and the qubit efficiency. Our protocol uses the keys generated by quantum key distribution and bit-flipping for privacy protection, making both outsider and insider attacks invalid. In addition, our protocol does not employ any other quantum technologies (e.g., entanglement swapping and unitary operations) except necessary technologies such as quantum measurements, which can reduce the need for quantum devices. Furthermore, the GHZ states are prepared by participants rather than by the third party, which can reduce potential security risks.