The application of semi‐quantum conception can provide unconditional secure communication for communicators without quantum capabilities. A semi‐quantum key distribution (SQKD) protocol based on four‐particle cluster states is put forward, which can achieve key distribution among one quantum party and two classical parties simultaneously. Furthermore, this protocol can be expanded to the χ‐party (χ>3) communication scheme. Compared with the existing multi‐party SQKD protocol, the proposed protocol and the extended one own more excellent time efficiency and qubit efficiency. The security of the proposed SQKD protocol under ideal circumstances is validated while the key rate under non‐ideal conditions is calculated.

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The introduction of the semi‐quantum concept makes secure communication easier to realize, but semi‐quantum key distribution (SQKD) is only half as efficient as quantum key distribution (QKD), or even lower. In particular, the efficiency is more worrying when the quantum sender distributes the key to several classical receivers. In article number 1800520, Nan‐Run Zhou and co‐workers propose a semi‐quantum key distribution protocol with four‐particle cluster states that can achieve key distribution among one quantum party and two classical parties simultaneously, which can be expanded to more than two classical communication parties. Compared with the existing multi‐party semi‐quantum key distribution protocol, the proposed protocol owns more excellent time efficiency and qubit efficiency. The protocol's security under ideal circumstances and key rate under non‐ideal conditions is analyzed.