A novel circular semiquantum private comparison protocol of equality without a pre-shared key based on \c{hi}-type states

Abstract: In this paper, we adopt \c{hi}-type states to design a novel circular semiquantum private comparison (SQPC) protocol which can determine the equality of private inputs from two semiquantum users within one round implementation under the help of a semi-honest third party (TP) who possesses complete quantum capabilities. Here, it is assumed that the semi-honest TP has the abilities to launch all possible attacks to steal useful information about two semiquantum users' private inputs but cannot conspire with anyone else. The travelling particles go from TP to Alice, Alice to Bob and back from Bob to TP. The security analysis turns out the proposed SQPC protocol can resist both the outside attacks and the inside attacks. The proposed SQPC protocol has no demand for unitary operations. Compared with some existing SQPC protocols of equality with quantum entangled states, the proposed SQPC protocol has some advantages more or less:(1)it requires no pre-shared key among different participants; (2)it doesn't need quantum entanglement swapping; and(3)it employs no delay lines.