LPHTA: A Lightweight and Privacy-Preserving Heterogeneous Traffic Aggregation Scheme for Fog-Cloud VANETs

Vehicular Ad Hoc Networks (VANETs) enable vehicles to report traffic conditions through vehicle to vehicle and vehicle to roadside communication. Such reports help traffic management systems estimate congestion and guide routing. Two main challenges arise in practical VANETs. Heterogeneous cryptographic systems hinder secure cross-domain communication and threaten vehicle privacy. Meanwhile, traffic management requires efficient aggregation without revealing individual routes. This paper proposes LPHTA, a lightweight and privacy preserving traffic aggregation scheme for fog and cloud assisted VANETs. LPHTA integrates heterogeneous signcryption to support secure communication between CLC and PKI entities. It also uses Paillier homomorphic encryption to aggregate encrypted reports at fog nodes, enabling the cloud to obtain intersection level traffic statistics. LPHTA also provides conditional privacy, ensuring anonymity during normal reporting while enabling traceability when necessary. Formal security analysis shows that LPHTA achieves IND-CCA2 and EUF-CMA under the elliptic curve discrete logarithm problem assumption. Simulation results demonstrate low computational and communication overhead, as well as stable network performance in dense and high mobility vehicular environments. These results indicate that LPHTA is suitable for practical traffic management applications.