In recent years, there have been growing interest and research efforts in
the area of Vehicular Ad-hoc Networks (VANET) because of the variety of services
it can offer. These services fall into the categories of safety applications and
non-safety applications. Safety is one of the most important goals of VANET since
enhanced safety reduces accidents and therefore can improve traffic conditions and
even save lives. Besides safety, other services such as Internet access, weather
forecast and geo-location information can enrich travel experience by providing travel
comfort, convenience and infotainment.
Safety in VANETs is of special concern because human lives are constantly at stake whereas
in traditional networks the major security concerns include confidentiality, integrity and
availability none of which involves primarily with life safety. Vital information cannot be
neither modified nor deleted by an attacker. Nonetheless, security in VANET also indicates
the ability to determine the driver responsibility while maintaining driver privacy. Information
about the vehicles and their drivers within must be exchanged securely and more importantly,
timely in that the delay of message exchange may cause catastrophic consequences such as collision
The wireless medium used in VANET has drawbacks that can render the network vulnerable to security
attacks such as interference, jamming and eavesdropping. In addition, the upper layers of VANET
protocol stack reference the Open System Interconnection (OSI) network model. Therefore vehicular
networks inherit the its vulnerabilities. Luckily, VANET can also benefit from the existing cryptographic
solutions for dealing security attacks.
Trust Grouping Framework
One of the core issues of VANET security is exchanging safety messages that keep neighboring vehicles aware of road conditions and hazardous situations. These messages fall into the categories of periodic and event-driven safety messages. Periodic message by its name is exchanged periodically several times per second with neighboring vehicles and it carries information such as vehicle location, speed and direction. Event-driven messages, on the other hand, are issued only when hazardous situations like accidents emerge within proximity. Intuitively, since lives are at stake, event-driven messages should be delivered to all vehicles of concern in as quickly as possible. Because encryption and decryption of the message cause extra time at both ends, the necessity of securing the message is at question. However, a false message or an intentional delay can also cause hazardous situations like collisions. Therefore a tradeoff must be found between speed and security.