A Post-Quantum Resistant Lightweight Key Authentication and Exchange Protocol for Smart Home Environments

In smart home environments, Harvest Now and Decrypt Later (HNDL) attacks pose a significant threat to long-term privacy. Traditional elliptic curve cryptography (ECC)-based authentication systems can be neutralized using the Shor algorithm on quantum computers, making it difficult to mitigate these threats. In this study, we propose a hybrid authentication and key exchange protocol designed to address the resource constraints of smart home systems, while introducing the NIST standard post quantum cryptography (PQC) to defend against HNDL attacks. The proposed protocol operates through four concise steps: (1) Setup and Registration for identities and pre-shared keys (PSK); (2) Key Agreement between the user and gateway using ML-KEM; (3) Session Key Distribution from the gateway to the smart device (SD) using the PSK; and (4) Mutual Authentication to verify the established key across all nodes. Formal verification using ProVerif and Scyther confirms the security of the proposed protocol, which achieved a communication cost of 7424 bits, representing a 44–82% reduction compared to existing PQC protocols. Furthermore, the proposed protocol demonstrated an execution time of 0.3205 ms, achieving a 74–90% and 60–74% improvement over existing ECC-based and PQC-based methods, respectively. Consequently, this study presents a quantum-resistant authentication protocol for smart-home environments that achieves a practical balance between security and efficiency.