Purpose: The framework of the Autonomous Vehicles (AVs) is facilitated by modern communication systems. In Real-Time (RT), the data is communicated to one another, and it is encouraged by AV. This AV also communicates with organizations stationed along the roadway, and navigates without human intervention. The dynamic and decentralized communication between vehicles and Roadside Units (RSUs) is integrated in Vehicular Ad Hoc Networks (VANETs). Then, there is no centralized structure for utilization in VANET. This distributed system faces difficulties in 2 areas: Authentication and security. The susceptibility to the network is increased by the unpredictable and risky features of AV, because there is currently no robust authentication system in place for multi-broadcast situations. Hence, the network is susceptible to security breaches, illegal access, data tampering, and service interruptions. During Handover Authentication (HA) between RSUs, critical security vulnerabilities are introduced by AV communication in ad-hoc networks, because of their dynamic topology and mobility patterns. Methodology: To address these issues, this study proposes a HA system for ad hoc AVs that uses blockchain technology. Using distributed controllers and Zero Knowledge Proofs (ZKPs), the proposed methodology enables rapid and safe authentication of AVs during handover between RSUs. To optimize authentication, decentralized Smart Network Controllers (SNCs) were used by the suggested method. This suggested method also eliminates the dependency on centralized entities and mitigates Single Point of Failure (SPoF) vulnerabilities. Findings: A private Blockchain network implementation makes the system transparent and immutable while providing tamper-proof storage for vehicle data. Simulation results demonstrate that the protocol achieves a 30.4 reduction in authentication latency, 27.8 lower packet loss rate, and a 23.5 improvement in throughput compared to EMT and GMT baseline protocols. Additionally, the system sustains a 95.2 success rate in mutual authentication under high vehicle density and maintains security integrity against impersonation, Sybil, and replay attacks. Originality/Value: The suggested protocol also mitigates SPoF risk of centralized systems and offers smooth Vehicle-to-Everything (V2X) services without charging any transaction fee. This method provides strong and scalable security for the communication of AVs in smart city systems. © 2025 Elsevier B.V., All rights reserved.