Verifiable event evidence sharing in VANETs via threshold multi-witness endorsement and controlled verification

Vehicular Ad Hoc Networks (VANETs) need to disseminate event evidence among vehicles that lack persistent trust relationships. Although traditional authentication and signature-based schemes can ensure message origin and integrity, they cannot prove the authenticity of the underlying events themselves. Moreover, the public verifiability of event evidence may lead to misuse of the evidence data by unauthorized third parties. To address these issues, this paper proposes VeShare-EV, a cryptographic framework for verifiable event evidence sharing tailored for infrastructure-assisted VANETs. VeShare-EV combines a threshold-based multi-vehicle witnessing mechanism with a policy-driven controlled verification mechanism. An event is considered trustworthy only when it is endorsed by a threshold number of independent witness vehicles. Meanwhile, by leveraging a dual-mode designated verifier mechanism for different categories of evidence, the framework selectively grants verification capabilities, enabling differentiated access control. The scheme adopts Shamir’s secret sharing technique in conjunction with bilinear pairing constructions. Its security is proven under the computational Diffie-Hellman assumption in the random oracle model. We further derive the theoretical computational and communication overhead of the core protocol processes and conduct performance evaluations based on the BLS12-381 curve. Experimental results show that the scheme exhibits near-linear scalability and good practical efficiency with respect to the threshold parameter and verifier pool size, demonstrating its feasibility for deployment in real-world VANET environments.