In this paper, we introduce an efficient and trustworthy conditional privacy-preserving communication protocol for VANETs based on proxy re-signature. The proposed protocol is characterized by the trusted authority (TA) designating the roadside units to translate signatures computed by the on-board units into one that are valid with respect to TA's public key. In addition, the proposed protocol offers both a priori and a posteriori countermeasures: it can not only provide fast anonymous authentication and privacy tracking, but also guarantee message trustworthiness for vehicle-to-vehicle communications. Furthermore, it reduces the communication overhead and offers fast message authentication and low storage requirements. We use extensive analysis to demonstrate the merits of the proposed protocol and to contrast it with previously proposed solutions. Copyright © 2012 John Wiley & Sons, Ltd.