The goal of VANETs is to develop an efficient and secure communication system applicable to vehicles to enhance driver's safety and comfort. Since information flowing through VANETs is inherently life-critical and sensitive to location privacy, vehicular communications should provide anonymity and authenticity without sacrificing efficiency. This makes it difficult to design a secure communication scheme for VANETs. In this paper, we propose the signature scheme which resolve the key update problem in VANETs using tamper-proof device. Using the scheme as a building block, we also propose the vehicle-to-vehicle communication protocol which provides desirable but conflicting functionalities such as anonymity, authenticity, unlinka-bility, non-repudiation, and traceability.