A traceable and verifiable CP-ABE scheme with blockchain in VANET

With the rapid development of Vehicular ad hoc networks (VANETs), secure communication in VANETs has been extensively studied. However, it is very challenging for VANETs to establish reliable data sharing for one-to-many users without access control. Attribute-based encryption (ABE) is a promising access control technique, which can maintain data confidentiality and is suitable for applications in VANETs. The current ABE scheme performs encryption and decryption of elements on the bilinear group, which is unfriendly for large-scale plaintexts and causes VANETs vulnerable to receive malicious or erroneous information. In this paper, we propose a variant attribute-based encryption access control scheme to achieve fine-grained access control for VANETs data shared in cloud and fog. It allows a message sender to determine which vehicles receive and decrypt messages based on the vehicle's attributes. We also employ a fusion of AES and CP-ABE to address the issue of key leakage caused by symmetric encryption key transferring. We implement a one-time key operation to make each ciphertext with its unique key and signature, which greatly improves the security of data transmission and provides tamper-proof for the plaintext. We also offer a novel method that treats roadside units as the constituent parts of a blockchain and publishes the device's public signature on the chain to validate the sender's identity. Compared with other existing CP-ABE schemes, our scheme is easily retrofitted to other encryption frameworks. Finally, performance evaluation reveals the security and efficiency of the proposed scheme based on theoretical analysis and experimental analysis.