A Novel Quantum Multi‐Party Private Set Intersection Protocol Based on Phase Encoding Without Third Party

Abstract The Quantum Private Set Intersection (QPSI) protocol, combining quantum technology, enables efficient extraction of the public elements of private sets while preserving the privacy of all parties. As known, existing solutions are mostly designed for two‐party scenarios or typically rely on an honest or semi‐honest third party to perform the private set intersection. In fact, establishing such third party may bring risks of single‐point failures in real scenarios. To address these issues, a Quantum Multi‐Party Private Set Intersection (QMPSI) protocol without third party is proposed for the first time. In this protocol, the quantum state phase encoding is applied to compute the intersection of participants' private set. According to this analysis, it can be seen that the presented protocol conducts a comprehensive correctness and security analysis, and simulates the core processes using IBM Qiskit to verify its feasibility. The proposed approach successfully solves the private set intersection problem while serving as a fundamental module for solving other multi‐party collaborative computation scenarios.