161 Copyright © 2012, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. Chapter 8 DOI: 10.4018/978-1-61350-477-2.ch008 INTRODUCTION A Vehicular ad hoc network (VANET) is an important and a special instantiation of Mobile ad hoc Networks (MANET) aiming essentially to increase road safety, yet it enables vehicles to share pertinent information on the road. To this end, vehicles must be able to route information and inform each other about potential ongoing events on the road. The inherent open architec- ture of VANETs, however, raises several network vulnerability and security issues. Unlike wired networks which can be protected by several layers of defense such as firewalls, attacks on Tahani Gazdar University of Manouba, Tunisia Abdelfettah Belghith University of Manouba, Tunisia Abderrahim Benslimane University of Avignon, France A Distributed Secure Architecture for Vehicular Ad Hoc Networks ABSTRACT In this paper, the authors propose a dynamic Public Key Infrastructure (PKI) for vehicular ad hoc networks to distribute the role of the central certification authority (CA) among a set of dynamically elected CAs. The election process is based on a clustering algorithm relying on trust levels and rela- tive mobility. Furthermore, the authors have adapted the Dynamic Demilitarized Zones to protect the elected CAs from malicious nodes and enable them to act as registration authorities (RA). Extensive simulations are conducted to evaluate the performance of the clustering algorithm and investigate the impact of the vehicle speed, the vehicle average arrival rate, and the percentage of confident vehicles on the stability and efficiency of the security infrastructure. The authors demonstrate the percentage of confident nodes has a little impact on these performance metrics and that the minimum number of CAs to cover the entire platoon.