S ECURITY IN M OBILE A D H OC AND S ENSOR N ETWORKS

The advancement and wide deployment of wireless communication technologies have revolutionized human lifestyles by providing the most convenience and flexibility ever in accessing Internet services and various types of personal communication applications. Recently, car manufacturers and telecommunication companies have been gearing up to equip each car with technology that allows drivers and passengers to communicate with each other as well as with the roadside infrastructure that may be located in some critical sections of the road, such as at every traffic light or any intersection or stop sign, in order to improve the driving experience and make driving safer. For example, Microsoft Corp.’s MSN TV and KVH Industries, Inc. have introduced an automotive vehicle Internet access system called TracNet, which can bring Internet service to any in-car video screen. It also turns the entire vehicle into an IEEE 802.11-based Wi-Fi hotspot, so passengers can use their wireless-enabled laptops to go online. Furthermore, by using such equipped communication devices, also known as onboard units (OBUs), vehicles can communicate with each other as well as with roadside units (RSUs) located at critical points on the road. A self-organized network can be formed by connecting the vehicles and RSUs, called a vehicular ad hoc network (VANET), and the RSUs are further connected to the backbone network. Increasing interest has been raised recently in the applications of roadside-to-vehicle communications (RVCs) and intervehicle communications (IVCs), aiming to improve driving safety and traffic management while providing drivers and passengers with Internet access. It is estimated that the market for vehicular communications will reach multiple billions of dollars by 2012. In VANETs, RSUs can provide assistance in finding facilities such as restaurants and gas stations, and broadcast traffic-related messages such as maximum curve turning speed notifications to give drivers a heads up. On the other hand, VANETs can enable vehicles to communicate with each other so that drivers can have better awareness of what is going on in their driving environment and take early action to respond to an abnormal situation. For achieving this, an OBU regularly broadcasts routine traffic-related messages with information on position, current time, direction, speed, brake status, steering angle, turn signal, acceleration/deceleration, traffic conditions, and traffic events [1]. In addition, emergency messages can be generated and sent by OBUs in case of emergent braking, traffic jam, or any accident. For example, as shown in Fig. 1, whenever there is an accident on a highway, several lanes can be blocked. Drivers can experience a long delay. However, the delay can be mitigated if drivers are informed in advance so that they can follow detour route or change lanes to avoid a traffic jam. Despite the advantages of a VANET, there are many challenges, especially in the aspects of security and privacy. As a special implementation of mobile ad hoc networks (MANETs), a VANET inherits all the known and unknown security weaknesses associated with MANETs, and could be subject to many security and privacy threats. It is obvious that any malicious behavior of users, such as a modification and replay attack with respect to the disseminated ABSTRACT