Three-party semi-quantum secure direct communication based on two communication models

Based on semi-quantum cryptography and utilizing W-state, this paper introduces two semi-quantum secure direct communication (SQSDC) protocols. SQSDC1 establishes a secret two-way communication channel between a quantum participant and two classical participants. SQSDC2 achieves efficient one-way communication from a quantum user to classical users. Security analysis demonstrates the asymptotic security of the protocols, effectively resisting intercept-measure-resend attacks and entangle-measure attacks from potential eavesdroppers. The efficiency analysis indicates high communication efficiency, with SQSDC1 achieving communication efficiencies of 20%, while SQSDC2 achieves a communication efficiency of 33.33%.