MCB-CPPA: An Efficient Conditional Privacy-Preserving Authentication Scheme Based on Message Classification for VANETs

Vehicular ad hoc networks (VANETs) can enhance traffic conditions through real-time communication, but vehicle-to-infrastructure exchanges in open channels require higher security and privacy. Numerous conditional privacy-preserving authentication (CPPA) schemes have been designed to ensure message authenticity. However, most CPPA schemes still suffer from many shortcomings, such as redundant authentication of messages, lack of effective identity revocation mechanism, and over-reliance on the authentication center. In order to address these concerns, an efficient certificateless CPPA scheme based on message classification (MCB-CPPA) is introduced for VANETs, which aggregates authentication for the same message across different vehicles and performs batch verification for identical messages from different vehicles, thus reducing redundant message validation. Furthermore, the scheme separates the processes of identity authentication and traffic message verification relying on both roadside units and vehicles to reduce security dependence on the authentication center. Regarding the certificateless signature in the MCB-CPPA scheme, we demonstrate existential unforgeability in the random oracle model (ROM) against the adaptive chosen message attack. Upon evaluation, it is revealed that the transmission and batch authentication overheads of this proposed scheme have been reduced by approximately 47. 7% and 51. 6% compared to existing state-of-the-art solutions. As a result, the proposed scheme successfully reduces the computational overhead and communication cost while satisfying the safety requirements of VANETs, making it more adaptable to the VANETs environment.