Optimized and Secure Hybrid Key Exchange Model for Post-Quantum Digital Communications

This paper presents an optimized hybrid key exchange model that combines Elliptic Curve Cryptography (ECC) and the Kyber-768 algorithm to enhance the efficiency and security of digital communications in the post-quantum era. The proposed approach leverages the computational efficiency of ECC alongside the quantum-resistant properties of Kyber, thereby ensuring both high performance and long-term resilience. The hybrid model was implemented in a real client–server environment, demonstrating the successful execution of key exchange, combination, derivation, and AES-256-GCM encryption–decryption processes. Experimental results show that the scheme achieves a consistently low total execution time of approximately ~8.653 ms, making it highly suitable for real-time communication and secure file transfer applications. Furthermore, the hybrid design provides enhanced layered security, as confidentiality is preserved unless both ECC and Kyber are simultaneously compromised. Therefore, this model establishes a scalable, quantum-safe communication foundation for critical infrastructure within Smart Systems, such as Cyber-Physical Systems (CPS) and Industrial IoT (IIoT).