Abstract. VANETs have the potential to dramatically increase road safety by giving drivers more time to react adequately to dangerous situations. To prevent abuse of VANETs, a security infrastructure is needed that ensures security requirements like message integrity, confidentiality, and availability. After giving more details on the requirements we propose a security infrastructure that uses asymmetric as well as symmetric cryptography and tamper resistant hardware. While fulfilling the requirements, our proposal is especially designed to protect privacy of the VANET users and proves to be very efficient in terms of computational needs and bandwidth overhead.