A Certificate Validation Protocol for VANETs

Vehicular ad hoc networks (VANETs) have received increased attention as the potential technology to enhance active and preventive safety on the road, as well as travel comfort. VANETs employ inter-vehicle and vehicle-to-roadside communications as means towards the reduction of the number of traffic accidents. On the other hand, intelligent traffic services are effective if they are associated with mechanisms that manage and establish trust between service providers and vehicles. Thus, the authentication of the suppliers of traffic condition information and the authorization of entities to access this information are essential. When public key certificates schemes are deployed in VANETs, they must be accompanied by efficient mechanisms for certificate revocation and validation. In this paper we address this issue, and a distributed, on-demand, scheme that is based on the online certificate status protocol for certificate status information is adapted to be applicable in VANETs. This scheme, originally proposed for MANETs, called ADOPT, uses caches of OCSP responses that are distributed and stored on intermediate nodes. In this paper we discuss ADOPT, and compare its efficiency with other certificate revocation and information dissemination protocols. The results show that ADOPT manages to rapidly identify and locate the status of a certificate without introducing significant storage costs.