Blockchain-based group key agreement protocol for vehicular ad hoc networks

Vehicular ad hoc network (VANET) has been attracting widespread attention because of its ability to improve traffic efficiency and safety. Since insecure wireless communication channels face various security threats (eavesdropping, tampering, forgery attack, etc.), many group key agreement protocols have been proposed for VANET. However, most of them rely on a trusted authority (TA) to perform authentication or group key generation. Excessive dependence on TA may lead to a single point of failure. Therefore, this paper designs a decentralized group key agreement protocol to solve this problem. TA is not involved in authentication or key agreement process after user registration. With blockchain technology, rode-side unit (RSU) and onboard units (OBUs) within its communication range can negotiate a group key without private information leakage. Moreover, the proposed protocol supports dynamic management (verification, update, and revocation) of vehicles' public keys. Formal security proof demonstrates that the proposed protocol meets basic security requirements. Besides, performance evaluation and comparison show that the proposed protocol requires lower computation costs and communication overheads than some existing protocols.