Efficient semi-quantum authenticated key agreement for dual-mode communication of multicast and unicast in smart grids

The operation of smart grids relies on the bidirectional flow of unicast and multicast (broadcast) information, and their security is typically ensured by authentication key agreement mechanisms based on classical cryptography. However, quantum algorithms threaten this security foundation. Existing semi-quantum authentication schemes fail to address the dual requirements of multicast and unicast keys for regionalized flexible management, nor do they balance the quantum burden on resource-constrained endpoints with authentication security in physical environments. To this end, this paper proposes a semi-quantum authentication and dual-key agreement scheme (SQADKA). It employs parallel distribution of a d -dimensional n -particle entangled system to generate a shared multicast key, while embedding random states within a single communication for two-factor authentication and unicast key generation. The multicast key can be used for broadcasting regional commands, while the unicast key protects private data exchange between smart meters and the neighborhood area network. Smart meters configured as classical users with two-factor authentication achieve quantum-enhanced security without complex quantum operations. Considering the dynamic membership of SGs, SQADKA allows SMs to join or leave a group while ensuring multicast key security. Additionally, the security of SQADKA has been analyzed through formal and informal security analyses. This scheme’s logic is verified and the comparison demonstrates advantages over similar schemes in terms of security, qubit efficiency, and communication complexity.