With significant technological advancements, Vehicular Ad-hoc Networks (VANETs), a form of Mobile Ad-Hoc Networks, have emerged as the most extensively utilized paradigm for intelligent transportation networks, with each vehicle outfitted with sensors serving as a mobile node. In order to guarantee traffic efficiency and safety, VANET systems are utilized to give real-time data about weather, traffic, and road conditions to vehicles. In order to provide exchange of messages in VANETs, the authenticity of vehicles becomes an important aspect that requires meticulous attention. In recent years, many authentication and group key distribution protocols have been presented, but they still suffer from performance efficiency and security vulnerabilities. In this work, we propose a multi-vehicle authentication protocol to provide safe communication in a VANET context. In our scheme, the trusted party server’s computational cost for authentication, group key encryption, and decryption is significantly less than the related schemes. Additionally, we present a theory of number-based group key distribution protocol to distribute the group key for the verified vehicles. Our scheme reduces the rekeying cost to \(\mathcal{O}(1)\) when a vehicle leaves or joins the group. The rigorous security analysis demonstrates that our proposed protocol ensures message authentication, forward and backward security, group key secrecy, and identity privacy while protecting the message against well-known security attacks. Performance analysis shows that our scheme significantly reduces the computation complexity, communication complexity, and storage complexity compared to existing works.