Efficient semi-quantum private comparison protocol of size relation based on high-dimensional Bell states

An efficient semi-quantum private comparison protocol is proposed with d-dimensional Bell states to assist two classical parties in comparing the size relation of their secret information. With the assistance of a third party (TP), Alice and Bob do not need to measure qubits or prepare new qubits, reducing the consumption of quantum resources. The presented protocol has a higher qubit efficiency than other similar protocols, since the legal participants can compare two bits of privacy (i.e., secret information unknown to others) each time with one qubit. Moreover, the proposed scheme offers a greater advantage when comparing larger private numbers, with the correctness of its outputs verified through analytical methods. Simulation experiments further verified the correctness of the proposed protocol, and security analyses demonstrated its robustness against external and internal attacks. Furthermore, the proposed semi-quantum private comparison protocol can be converted into an efficient semi-quantum key distribution protocol.