A practical privacy-preserving communication scheme for CAMs in C-ITS

In a Collaborative Intelligent Transportation System (C-ITS), vehicles send collaborative awareness messages (CAMs) carrying information such as speed, position, and identity, to interact with other vehicles and to obtain transportation services. Traditionally, CAMs are broadcasted in plaintext over unsafe networks, which may leak sensitive information of the vehicle. On one hand, many existing works attempting to solve this problem focused on anonymous authentication, but ignored the confidentiality of CAMs. Conversely, some other attempts trying to keep the privacy of CAMs have backward security problems in key management or vehicle revocation. Therefore, in this paper, we present a practical privacy-preserving communication scheme for CAMs in C-ITS. To ensure the privacy of a vehicle's identity, our scheme mainly uses the re-randomizable PS signature method to realize anonymous authentication; and to meet backward security, we use the complete subtree method to realize both key management and vehicle revocation. In more details, our proposal fulfills more security and privacy requirements, such as correctness, anonymity, traceability, revocability, backward security and anti-illegal message dissemination, while also hiding the content of CAMs.