Vehicular ad hoc networks (VANETs) are advanced instances of mobile ad hoc networks with the aim of enhancing the safety and efficiency of road traffic. The basic idea is to allow arbitrary vehicles to broadcast ad hoc messages (e.g. traffic accident notifications) to other vehicles and remind drivers to change their routes immediately or slow down to avoid dangers. However, some concerns on security and privacy are also raised in this environment. Messages should be signed and verified before they are trusted while the real identities of vehicles should not be revealed to guarantee source privacy, but they must be still traceable when VANETs were abused (e.g. sending a fake message). Many related works have been presented in the literature so far. They can be generally divided into two constructions, where one is based on pseudonymous authentication and the other is based on group signatures. However, both of the two constructions have some drawbacks. In a pseudonymous-authentication-based scheme, a large revocation list is usually transmitted among vehicles. A group-signature-based scheme needs a large amount of computations for revocation checking. Furthermore, most of the previous schemes cannot support privacy preservation between roadside units (RSUs) and vehicles. Consequently, in this paper, we come up with a provably secure and strong privacy preserving protocol based on the blind signature technique to guarantee privacy and fulfill other essential security requirements in the vehicular communication environment. Furthermore, compared with other similar works, we offer an efficient tracing mechanism to trace and revoke the vehicles which abused the VANETs. Finally, we provide security analysis to show that our proposed scheme is secure.
