Multi‐Party Semi‐Quantum Private Comparison Protocol of Size Relation with <i>d</i> ‐Level GHZ States

Abstract A new multi‐party semi‐quantum private comparison protocol of size relation is designed based on d ‐level GHZ states. Multiple classical participants could compare their privacies while keeping them secure under an ideal environment. Compared with some similar protocols, the classical participants in the designed protocol do not need to prepare and measure quantum states. Besides, the qubit efficiency of the protocol reaches 33.33%. It is demonstrated that the output result of the proposed protocol is correct. Finally, security analysis manifests that the proposed protocol behaves well in withstanding intercept‐resend attack, measure‐resend attack, entanglement attack, Trojan horse attack, and so on.