LEPA: Low-Overhead and Efficient Privacy-Preserving Authentication Scheme in VANETs ^†

The dynamic nature of Vehicular Ad-hoc Networks (VANETs) necessitates robust authentication mechanisms to prevent adversaries from compromising vehicle privacy. To address privacy concerns, many existing approaches employ pseudonyms in place of real vehicle identities. However, the use of a single pseudonym is insufficient, as vehicle trajectories can still enable tracking. Consequently, vehicles must frequently change pseudonyms, typically selecting them from a pre-assigned pool, to ensure unlinkability and preserve privacy. In most existing schemes, a central authority issues certificates corresponding to each pseudonym, which vehicles present for authentication. While effective, this approach incurs significant computation, storage, and communication overhead, particularly in managing certificate revocation lists (CRLs), since each vehicle may possess a large number of pseudonyms. To address these challenges, we propose a Low-overhead and Efficient Privacy-preserving Authentication (LEPA) scheme for VANETs, leveraging Merkle Hash Trees (MHTs) and Cuckoo Filters (CFs) to efficiently manage pseudonym sets and revocation. We analyze the security of the proposed scheme against various attacks and demonstrate, through performance evaluation, that LEPA significantly reduces authentication and revocation overhead while maintaining strong privacy and security guarantees.