A two level privacy preserving pseudonymous authentication protocol for VANET

Vehicular ad hoc network (VANET) is gaining significant popularity due to their role in improving traffic efficiency and safety. However, communication in VANET needs to be secure as well as authenticated. The vehicles in the VANET not only broadcast traffic messages known as beacons but also broadcast safety critical messages such as electronic emergency brake light (EEBL). Due to the openness of the network, a malicious vehicles can join the network and broadcast bogus messages that could result in accident. On one hand, a vehicle needs to be authenticated while on the other hand, its private data such as location and identity information must be prevented from misuse. In this paper, we propose an efficient pseudonymous authentication protocol with conditional privacy preservation to enhance the security of VANET. Most of the current protocols either utilize pseudonym based approaches with certificate revocation list (CRL) that causes significant communicational and storage overhead or group signature based approaches that are computationally expensive. Another inherent disadvantage is to have full trust on certification authorities, as these entities have complete user profiles. We present a new protocol that only requires honest-but-curious behavior from certification authority. We utilize a mechanism for providing a user with two levels of pseudonyms named as base pseudonym and short time pseudonyms to achieve conditional privacy. However, in case of revocation, there is no need to maintain the revocation list of pseudonyms. The inherent mechanism assures the receiver of the message about the authenticity of the pseudonym. In the end of the paper, we analyze our protocol by giving the communication cost as well as various attack scenarios to show that our approach is efficient and robust.