A Unified Hybrid ECDHE–ML-KEM-768 Key Exchange Scheme for Quantum-Resilient Mobile Communication
The advent of quantum computing poses a significant threat to conventional public-key cryptographic systems, particularly resource-constrained mobile and cyber-physical environments. To address this challenge, this study proposes an implementation-oriented unified hybrid key derivation framework that integrates the Elliptic Curve Diffie–Hellman Ephemeral (ECDHE-P256) and post-quantum ML-KEM-768 algorithm for quantum-resilient secure communication. The proposed approach combines independently generated classical and post-quantum shared secrets through a lightweight mixing step followed by HKDF-SHA256 extraction and expansion to derive a unified 256-bit session key. This design preserves forward secrecy while enhancing resilience against quantum adversaries without requiring substantial modifications to the existing communication infrastructures. The framework was implemented on a heterogeneous testbed consisting of an x86_64 client and ARM64-based Android device. Experimental evaluations were conducted across 27 test configurations under three network latency conditions (50, 150, and 500 ms) using payload sizes of 64, 1024, and 10240 KB. Each configuration was executed for 1000 iterations to ensure statistically reliable measurements. The results demonstrate that, compared with standalone ECDHE-P256 and standalone ML-KEM-768, the proposed hybrid framework introduces only minimal computational overhead while maintaining stable resource utilization. Furthermore, network latency contributes more significantly to end-to-end communication delay than cryptographic processing overhead, indicating that the integration of classical and post-quantum cryptographic mechanisms does not constitute a major performance bottleneck. Overall, the proposed implementation-oriented framework provides a practical and lightweight transition strategy to quantum-resilient secure communication in heterogeneous mobile, IoT, and cyber-physical environments.