With the advent of autonomous vehicles, intelligent transportation systems based on the provision of real-time Vehicle-to-Vehicle (V2V) communications have become critical for enhancing road safety, traffic efficiency, and cooperative mobility. However, these communications between vehicles are significant because adversaries can act as a compromised node, traffic between them might be intercepted, or an attacker might inject false information, resulting in dangerous incidents. Attacks like phantom traffic jams caused by Sybil attacks, repeated broadcast 'Clear Path' messages leading to very close collisions that sophisticated security mechanisms are more important than ever. This study presents Continuous Authentication at Random Intervals (CARI), a security system tailored to the context of autonomous vehicle networks that offers the integrity of each message, but also adds a degree of randomness to the authentication process in the communication of the vehicles. As opposed to existing periodic or fixed-timing standards, CARI uses a randomized verification period making tampering, spoofing, and replay attacks much more challenging to execute.