EPRU: Efficient and Privacy-Aware Reputation Update Scheme With a Dual-Threshold Mechanism for Vehicular Platoons

Vehicular platooning demands secure and trustworthy inter-vehicle communications to maintain platoon stability, traffic efficiency, and driving safety. Existing privacy-preserving authentication schemes protect message integrity over open channels but often overlook the credibility of message content, allowing authenticated yet misleading data. Reputation management frameworks address this by evaluating vehicle behavior, yet most employ periodic updates, delaying detection of sudden misbehavior. This paper proposes a reputation-based authentication mechanism (EPRU) that establishes trust between vehicles by evaluating vehicle behavior and historical records, thereby ensuring the reliability of message transmission between vehicles. Our EPRU incorporates a dynamic aggregation trigger mechanism that updates vehicle credit scores based on verified feedback collected in real time, thereby accurately reflecting behavioral changes. Furthermore, a combination of ElGamal encryption and homomorphic encryption is employed to safeguard vehicle identities and feedback data during transmission and processing. Formal security proofs and extensive analysis demonstrate resistance to forgery, replay, and modification attacks, ensuring the confidentiality, integrity, and authenticity of both messages and feedback data. Experimental results demonstrate that our EPRU reduces computation overhead by at least 3.05% and communicational cost by 37.5% compared with recent state-of-the-art schemes, highlighting its practicality and efficiency for real-time, privacy-aware vehicular platoon systems.