New Semi-Quantum Key Agreement Protocol Based on the χ-Type Entanglement States

A new two-party semi-quantum key agreement protocol is proposed with the four-particle chi-type entanglement states. In this protocol, the shared secret key is generated by using Bell measurement, Z-basis measurement, sequence replacement operations and unitary operations. The one-way semi-quantum key agreement protocol can resist the Trojan horse attack naturally and both participant attack and external one. Compared with other similar two-party quantum key agreement protocols, the presented protocol is relatively efficient since the random collapse of quantum entanglement states reduces the requirement on quantum operations, without involving the four-qubit joint measurements.