SAGA: A Lightweight Authentication and Key Agreement Protocol for Resource-Asymmetric Smart Environments with Safe Service

Smart factories and homes represent resourceasymmetric environments where gateways offer abundant resources, while user and edge devices remain constrained. Existing authentication and key agreement (AKA) protocols for the settings typically overlook threats from malicious gateways and cannot reconcile dynamic anonymity with minimal overhead. To address these challenges, we propose the Secure dynamic Anonymity updates and Gateway-side secure Authentication (SAGA), a lightweight AKA protocol based on three synergistic layers: dual-threshold Shamir's Secret Sharing (SSS) to distribute trust across multiple gateways, a Merkle Tree mechanism with one-time password algorithm based on hash chains (HOTP) for efficient gateway verification, and an active shared key-refresh method to maintain dynamic anonymity and session keys. Formal security proofs using Burrows-Abadi-Needham (BAN) logic and ProVerif validate SAGA's rigorous security, while experimental results show it achieves stronger security properties with lower computational and communication costs than existing schemes.