Multi-Party Semi-Quantum Key Agreement Protocol Based on the Four-Qubit Cluster States

A multi-party semi-quantum key agreement protocol was proposed based on delegating quantum computation with the four-qubit cluster states. By randomly inserting confusion states into the encoding particle sequences, the proposed protocol can defend against the eavesdropping attack from quantum center. Since quantum center does not perform joint measurement until all participants have completed the encoding processes, the protocol is immune to the participant attack. In addition, the protocol is free from outside attack because of the properties of entanglement states. And the qubit efficiency of the proposed multi-party semi-quantum key agreement protocol is higher than those of most existing multi-party quantum key agreement protocols when more than five participants are involved. It is demonstrated that the proposed multi-party semi-quantum key agreement protocol is effective and fair.