ECHO: Efficient Certificate Updating Scheme by Vehicle-to-Vehicle Communications

Roadside units (RSUs) aided certificate service is a promising approach for ensuring security and privacy preservation in vehicular ad hoc networks (VANETs). In existing approaches, a vehicle can update certificate only when it passes by RSUs, however, this is impractical in many scenarios. Consequently, if there are no RSUs on the original driving trip, drivers have to adjust routes which means wasting time and money (oil). More seriously, traffic jams may occur nearby RSUs. In this paper, we propose ECHO, an efficient certificate updating scheme by Vehicle-to-Vehicle communications. In ECHO, by adopting the geographic routing protocols, a vehicle cannot only send the certificate request to immobile RSUs but also inform an RSU where the response message should be sent back. Thereafter, two strategies, estimating locations and employing intersection buffer unit, are studied. ECHO would not leak the trace of vehicles. Furthermore, academic analysis demonstrates that our scheme can guarantee vehicles to update certificate successfully even they are far from RSUs.