Privacy-aware revocation in VANETs with a Blockchain using accumulator

In recent years, Vehicular Ad-hoc Networks (VANETs) have gained widespread acceptance to enable vehicles to communicate and exchange critical information, such as road conditions, traffic congestion, speed, and vehicle locations. Nonetheless, the wireless nature of VANET communication renders it susceptible to various security attacks. To counter these vulnerabilities, privacy-preserving authentication schemes play a crucial role. Many of these schemes rely on Public Key Infrastructure (PKI) to mitigate security risks, ensuring authentication and message integrity through public key certificates. However, a significant drawback of these schemes arises from utilizing the Certificate Revocation List (CRL), which introduces notable delays. In addition, vehicular networks are time-sensitive, and prolonged delays may lead to severe consequences. Moreover, CRL checking can inadvertently leak sensitive vehicle information, making PKI-based schemes impractical for VANETs. To address these challenges, we propose a privacy-preserving revocation mechanism based on a zero-knowledge accumulator, tailored specifically for VANETs. This mechanism significantly reduces the time spent checking revoked certificates while preserving user privacy. Furthermore, by utilizing Blockchain technology to publish revoked certificates in a distributed manner, we can reduce the time required for distribution, decrease network congestion, improve efficiency, and eliminate reliance on a single central authority. Additionally, our approach aims to overcome the issue of non-membership witness updates in batch mode. Our proposed privacy-aware scheme has been rigorously evaluated using the automatic verification tool ProVerif. The results confirm that our solution guarantees the desired properties of anonymity and unlinkability. Through extensive simulation and performance analysis, we demonstrate that our scheme is not only privacy-preserving but also an efficient and practical solution for real-world deployment in VANETs.