Certificateless Aggregate Message Authentication for Hierarchical Trusted Authority based VANET

In VANET, vehicles periodically transmit beacon messages to the neighboring vehicles and the RSU. To establish the authenticity of these messages, a number of digital signature schemes have been proposed in literature. Many of these schemes enable an RSU to perform aggregate verification of the signatures to deal with high vehicle density scenarios. These schemes are either based on traditional PKC concept involving certificate management overhead or identity based cryptography having key escrow problem. Further, these schemes require the existence of OBU device which is resistant to side channel attacks. In this paper, we propose a hierarchical trusted authority privacy preserving certificateless aggregate signature scheme for VANET. In addition to providing message authentication, integrity and non-repudiation, our scheme is resistant to message forgeability attack. The proposed scheme assumes hierarchical organization of network such that vehicles operate under multiple trusted authorities (TA) which in turn are controlled by single root TA. Using our scheme, the entity could verify messages received from vehicles which operate under multiple TAs. The proposed scheme is free from key escrow problem and resistant to side channel attacks on OBU. It also possesses conditional linkability such that originator of a message could be revealed whenever required. Simulations confirm the efficient nature in terms of verification delay as compared to other well known schemes proposed in literature.