PVCA: Privacy-Preserving and Verifiable Cross-System Authorization for Platoon Communications in VANETs

Abstract

Vehicle platoon, an increasingly significant technology in vehicular ad hoc networks (VANETs), effectively reduces energy consumption and environmental pollution, mitigates traffic congestion, and enhances road capacity and traffic safety. Collaborative communication between platoons is available to promote the reliability of data dissemination, ameliorate driving strategies, and further strengthen traffic efficiency. Nevertheless, existing efforts for secure multi-platoon data dissemination still face the following issues: (i) lack of a direct authorization strategy for platoons working on different systems; (ii) no effective mechanism to protect vehicle privacy during platoon communications; (iii) absence of a practical verification approach for cross-system ciphertext transformation. This paper builds a privacy-preserving and verifiable cross-system authorization (PVCA) scheme to mitigate the above issues. Specifically, we first put forth the optimized anonymous identity-based broadcast encryption (IBBE) and policy-hiding attribute-based encryption (ABE) protocols to adapt platoon communications while protecting identity and attribute privacy. After that, the authorized token bridging the proposed protocols is designed to enable ciphertexts of IBBE format to be transformed into new ciphertexts of ABE format, enabling flexible authorization. Furthermore, inspired by the Fujisaki-Okamoto transformation, we devise an efficient zero knowledge proof of knowledge protocol, making our PVCA achieve verifiability and fairness. Rigorous security proof and analysis demonstrate that our PVCA is not only secure against chosen plaintext attacks and collusion attacks, but also satisfies the necessary security requirements. We implement a prototype of PVCA (on a desktop computer and Raspberry Pi) and provide a simulation utilizing NS-2 to validate its feasibility for platoon communications in VANETs. The results indicate that, compared to the state-of-the-art ciphertext transformation solutions, PVCA reduces the running time for original ciphertext generation, transformation, and decryption by at least 91.57%, 49.87%, and 50%, respectively, while compressing the original ciphertext and authorization token sizes by over 78.07% and 15.20%.