The increasing mobility of people has caused a high cost for societies as consequence of the increasing number of traffic congestion, fatalities and injuries. Vehicular Ad-Hoc Networks (VANETs) envisage supporting services on Intelligent Transportation Systems (ITSs), as collective monitoring of traffic, collision avoidance, vehicle navigation, control of traffic lights, and traffic congestion management by signaling to drivers. VANETs comprise vehicles and roadside equipments owning wireless interfaces able to communicate among them by wireless and multi-hop communication.

VANETs are prone to interference and propagation issues, as well as different types of attacks and intrusions, that can harm ITS services. These networks are characterized by high mobility nodes, wireless links subject to interference, fading due to multipath propagation and highly changing network topologies. The absence of central entities increases the complexity of security management operations, particularly, access control, node authentication and cryptographic key distribution, allowing the participation of misbehaving (malicious or selfish) nodes in the network and posing nontrivial challenges to security design. Further, wireless communication is susceptible to jamming, eavesdropping and interferences making easy to damage information and service security. Albeit all these drawbacks, it is well known today that guaranteeing information integrity, authenticity, confidentiality, non-repudiation, and, particularly, availability of network services and information are prerequisite for the successful deployment of VANETs.