<p>A secure three-party semi-quantum dialogue (SQD) protocol is presented based on GHZ states. The SQD protocol enables one quantum-capable participant and two classical participants to exchange secret messages without violating the constraints of a semi-quantum environment. By leveraging the entanglement correlations inherent to GHZ states, the protocol resists various quantum attacks, including the intercept-and-resend attack, flip attack, information leakage problem, entangle-and-measure attack, and Trojan horse attack. Unlike previous approaches, the design does not require decoy photons or quantum memory, thereby eliminating the need for quantum delay lines on the part of classical users. A single-round eavesdropping detection mechanism is employed to verify channel integrity, ensuring both security and operational simplicity. Security and efficiency analyses confirm the protocol’s robustness and practical feasibility under realistic constraints, offering a viable advancement in semi-quantum cryptographic communication.</p>