“…Security challenges are the critical and indispensable issues to solve in the first place in order to build realistic and practical VANET applications (Yousefi et al, 2006;Parno and Perrig, 2005;Hubaux et al, 2004;Raya et al, 2006b). The existing security research work in VANETs include Self-Organising Traffic Information System (SOTIS) (Wischhof et al, 2003), security and privacy issues (Raya and Hubaux, 2005;Papadimitratos et al, 2006aPapadimitratos et al, , 2006bHubaux et al, 2004;Plobl et al, 2006;Dotzer, 2006), fast authentication (Liu et al, 2006;Parno and Perrig, 2005), secure data aggregation (Picconi et al, 2006;Raya et al, 2006a), and detecting and correcting malicious data (Raya et al, 2006a;Golle et al, 2004), and so on. Among these security challenges, we focus on the reliable traffic information propagation through multiple vehicles.…”