MA‐LCPPA: A Multi‐Aggregator Lattice‐Based Conditional Privacy‐Preserving Authentication Scheme for Scalable and Quantum‐Secure VANETs

ABSTRACT Vehicular ad hoc networks (VANETs) are fundamental to intelligent transportation systems (ITS), enabling secure and low‐latency vehicle‐to‐vehicle (V2V) and vehicle‐to‐infrastructure (V2I) communication. Conditional privacy‐preserving authentication (CPPA) is essential for safeguarding message integrity and anonymity, yet traditional ECC‐ and pairing‐based CPPA schemes are both computationally intensive and vulnerable to quantum attacks. Although lattice‐based CPPA (L‐CPPA) schemes offer post‐quantum resistance and batch verification, their reliance on a single roadside unit (RSU) introduces verification bottlenecks and a single point of failure in dense traffic scenarios. To overcome these limitations, we propose a multi‐aggregator lattice‐based CPPA (MA‐LCPPA) framework that distributes verification tasks across cooperating RSUs and integrates a ( k , n )‐threshold traceability mechanism. This design significantly reduces verification delay, improves scalability and enhances fault tolerance while maintaining conditional privacy and post‐quantum security. Formal analysis demonstrates unforgeability, traceability and resilience against replay, impersonation, and collusion attacks under the hardness of the ISIS problem. Simulation results confirm that MA‐LCPPA reduces verification delay by over 50% and lowers RSU computation costs, with minimal communication overhead, making it a scalable and quantum‐secure solution for next‐generation vehicular networks.