The advent of 6G communications technology will bring about a transition from the “Internet of Everything” to the “Intelligent Connection of Everything”. 6G-enabled vehicular ad hoc networks (VANETs) will enjoy lower latency, higher speed, and greater capacity network services. Nevertheless, achieving secure data sharing will be an even tougher challenge. Given this, we propose an attribute-based data sharing scheme with blockchain for 6G-enabled VANETs. First, we propose an efficient multi-tree-based user revocation mechanism. With the Chinese remainder theorem, our mechanism supports user batch revocation and batch joining. Second, we achieve distributed data storage by utilizing the blockchain and smart contracts. To solve the problem of insufficient storage capacity on the blockchain, we adopt a combination of on-chain and off-chain storage. Third, to reduce the computation burden on users, our proposal supports online/offline encryption and verifiable outsourced decryption. Meanwhile, our mechanism supports policy hiding, data revocation, and cross-domain data sharing. The proposed scheme is proven to satisfy the indistinguishability under chosen plaintext attack (IND-CPA) in the standard model. Theoretical analysis shows that our mechanism outperforms existing schemes in functionality and security. Simulation experiments show that our proposal is efficient and suitable for 6G-enabled VANETs.

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.

Vehicular fog computing (VFC), as an extended model of fog computing, combines fog computing with traditional in-vehicle networks to provide real-time response services for users. However, in such a dynamic system architecture, achieving secure and efficient data sharing is an enormous challenge. Ciphertext-policy attribute-based encryption (CP-ABE) is widely regarded as an excellent way of achieving one-to-many data sharing. Nevertheless, several practical challenges hinder its widespread application in VFC, such as inefficient attribute revocation, single-factor access control, and centralized data storage. For this purpose, we design a multifactor combined data sharing scheme for VFC with CP-ABE and blockchain (MC-DS-VFC, in short). We first propose an efficient attribute revocation mechanism that does not require complex key update operations. We then embed time, user attributes, and access interests into data sharing for more fine-grain access control, which enables users with sufficient attributes to efficiently access real-time shared data according to their access interests. Finally, we combine the interplanetary file system (IPFS) and the blockchain maintained by roadside units (RSUs) to achieve distributed collaborative storage. Furthermore, our mechanism also supports user traceability, attribute joining, online/offline encryption, and verifiable outsourced decryption. Our proposal is shown to satisfy the indistinguishability under chosen plaintext attack (IND-CPA) in the standard model. Theoretical analysis and simulation experiments indicate that the MC-DS-VFC scheme is efficient and practical for VFC.