Publicly Accountable Data-sharing Scheme Supporting Privacy Protection for Fog-enabled VANETs

Vehicle ad hoc networks (VANETs) provide a convenient mobile communication environment for vehicles, pedestrians, and infrastructure. However, data confidentiality, access permission leakage, and privacy disclosure, are major issues of concern in such systems. Therefore, we present a publicly accountable data-sharing scheme for VANETs based on an expressive ciphertext policy attribute-based encryption (CP-ABE) algorithm. In this paper, we use white-box traceability and auditing technology to enforce accountability of both traitors and the key authority, and we employ two authorities to generate user keys collaboratively to weaken the power of one component and prevent the authority from tampering with users' identities. Considering the flexible change of vehicle attributes, we implement the revocation of malicious users or vehicles by updating partial keys and ciphertexts related to revoked user's attributes. Our method also supports attribute revocation and attribute update to deal with the complex and changeable environments of VANETs and achieves privacy preservation by adopting partial policy hiding technology. Multiple fog nodes are deployed at the edge of the cloud server to assist users who are short on resources in completing the encryption and decryption calculations. Comprehensive experimental results indicate that the proposed scheme has many advantages over others in terms of key storage consumption and the computational time consumption of encryption and decryption operations.