Improvement of Measure-Resend Semi-Quantum Private Comparison Scheme Using GHZ States

Recently, Yan et al. propose a measure-resend semi-quantum private comparison (SQPC) scheme based on eight kinds of initial GHZ states (Comput Mater Con, 2019, 61: 877). It is pointed out in this paper that Yan et al.'s scheme cannot defeat the double CNOT attacks from Eve, as she can distinguish the actions the classical communicants take. This paper suggests an improvement for this scheme mainly on the following two points: (1) reducing the number of kinds of initial GHZ states to one kind; and (2) making Eve have no knowledge about the genuine orders of the particles reflected to the quantum user. As a result, compared with the original scheme, the improved one has better practical implementation convenience and better security.