Accountable Attribute-Based Data-Sharing Scheme Based on Blockchain for Vehicular Ad Hoc Network

Vehicular ad hoc network (VANET), as one of the bases of intelligent transport systems, plays an essential role in improving road traffic safety. Nevertheless, in such a complicated, distributed, and highly mobile network structure, how to achieve secure data sharing is a great challenge. The ciphertext-policy attribute-based encryption (CP-ABE) is a potential method to realize one-to-many data sharing for VANET. However, the key abuse problems of users and attribute authorities (AAs) incur many security concerns for VANET. Both issues are extremely important because the attribute keys directly affect users' access to shared data. To solve the above issues, we propose an accountable attribute-based data-sharing scheme with the blockchain technology (AT-DS-VAHN, in short). For AAs key abuse, we use the consortium blockchain maintained by AAs to achieve distributed key storage and distribution. The attribute keys generated by each AA and its key distribution records are recorded on the blockchain in the form of transactions. Based on the traceability of blockchain, the key abuse behavior of AAs can be caught and prosecuted. For user key abuse, we achieve white-box traceability and efficient user revocation. Based on the principle of traceable-then-revocable, malicious users can be tracked and then revoked directly from the system without complex operations. Besides, to reduce the computation burden on users, our proposal supports online/offline encryption and verifiable outsourced decryption. Security and efficiency analyses show that our proposal is secure and efficient, with high practicability and reliability for VANET.