Two-party semi-quantum key agreement protocol for seven-particle entangled states in collective noise channels

Abstract The semi-quantum key agreement (SQKA) is a combination of the ‘semi-quantum’ concept in the quantum key agreement (QKA), which aims to reduce the requirements on the quantum ability of the participants while maintaining the security of the key agreement. In this paper, two novel two-party SQKA protocols based on seven-particle entangled states and delegated quantum centers in the collective noise channels are proposed. In the two SQKA protocols, only the quantum center possesses full quantum capabilities, while other participants have only partial quantum abilities. The classical party, on the other hand, only needs to perform Z-basis measurement on the classical basis. Due to the properties of entangled states, the two SQKA protocols can resist internal and external attacks. Furthermore, this paper provides a comprehensive analysis of the security of the proposed protocols, illustrating their resilience against various forms of attacks such as eavesdropping, intercept-resend attacks, and entangle-measure attacks. The results indicate that both protocols perform well in collective noise channels while maintaining high security even under noisy conditions. Moreover, eavesdropping simulation can detect whether there is eavesdropping behavior in the communication process. Finally, a comparison with existing protocols shows that the two proposed protocols exhibit higher qubit efficiency.