Ensuring the confidentiality of message transmission is a fundamental security requirement for communications in Vehicular Ad hoc NETworks （VANETs）. While utilizing symmetric group keys to encrypt messages， it is hard for system manager to trace inner attackers. Therefore， an attribute-based encryption scheme for VANETs was proposed. The scheme enables tracking and revocation of malicious vehicles and fine-grained division of vehicle access rights； meanwhile， the scheme allows multiple authority centers to distribute attributes and their corresponding keys independently， preventing compromised authority centers from forging attribute keys that are managed by other authorities， thus guaranteeing a high security for communication and collaboration among multiple institutions. This scheme was proven indistinguishable under q-DPBDHE2 （q-Decisional Parallel Bilinear Diffie-Hellman Exponent） assumption； and experimental results of encryption and decryption overhead comparison of this scheme and similar schemes show that while the number of attributes is 10， the decryption overhead of the proposed scheme is 459.541 ms， indicating that the scheme is suitable for communication encryption in VANETs.

In order to address problems concerning communication security and privacy preservation in Vehicular Ad hoc Network （VANET）， a revocable aggregate signature authentication scheme for VANETs was proposed. For protecting user privacy and enhancing authentication efficiency， the proposed scheme utilized anonymous authentication， tamper-proof device and aggregate signature technique. For realizing vehicle revocation， the vehicle was required to generate signatures with member secret keys distributed by the Road-Side Unit （RSU）. The RSU would check the vehicle identity when the vehicle entered its communication scope， and it would not distribute member secret keys to vehicles in the revoke list. Thus， malicious vehicles could not generate valid signatures. When the input traffic volume came up to 600 vehicles per hour for each entrance lane in the simulated intersection， the proposed scheme saved at least 33.77% of authentication overhead compared to certain schemes of the same kind. The outcome of simulation experiment shows that the proposed scheme is suitable for resource-limited VANET environment.