A trust based adaptive privacy preserving authentication scheme for VANETs

In vehicular ad hoc networks (VANETs), the exchanged messages among vehicles can effectively improve traffic safety and efficiency. Since the nature of open communication in VANETs, it is necessary to verify the legitimacy of vehicles to prevent illegal vehicles from participating in VANETs. In order to reveal the real identities of malicious vehicles, many conditional privacy preserving authentication schemes have been proposed. While, unconditional privacy preserving is also need for honest vehicles. However, the single conditional or unconditional privacy preserving cannot meet the privacy needs of various vehicles. In this paper, we propose a trust based adaptive privacy preserving authentication scheme. Under the assumption that the external system provides the trust values of vehicles and drivers, the scheme can provide unconditional privacy preserving with different trust levels for high trusted vehicles, while conditional privacy preserving is adopted for low trusted vehicles. In addition, considering the public identities of vehicles and the many-to-many relationship between vehicles and drivers, we introduce a ternary based identity representation method to generate the identities of vehicles, drivers and roadside units. And then, we propose a three entity authentication algorithm to verify the legitimacy of entities. Finally, the formal verification and security analysis are carried out, and the scheme has the characteristics of supervisability and adaptive privacy preserving. Moreover, in order to resist quantum attack, the latest lattice-based encryption and signature algorithms are adopted, and then the computation and communication costs are analyzed in detail.