Contribution to the Intelligent Transportation System : security of Safety Applications in Vehicle Ad hoc Networks

The development of transportation all over the world has been providing a lot of benefits for many aspects of human life. Intelligent Transportation Systems (ITS) are advanced applications that aim to make the transport networks safer, more convenient and smarter. According to their usages, they can be classified into two types of ITS applications, which are safety applications and non-safety applications. Vehicular ad hoc network (VANET) is a key component of ITS since it enables communications among transportation units. These communications support different ITS applications with various properties. Between two types of applications, we are interested in safety applications which have tighter quality and security constraints. Depending on an applied scenario of a given safety application, the exchanged information among vehicles must be broadcast locally within one-hop communication and/or also be notified to vehicles in large range. The main objective of this thesis is to improve the performance of safety applications in term of the quality of service and security, in both one-hop communication and multi-hop communication. We focus on reliability, connectivity and Denial of Services (DoS) attack. We study and propose technical solutions coming from lower layers (Physical, MAC and network layers) which play a fundamental role in mitigation to challenges created by the nature of the vehicular environment. Firstly, we introduce a reliable scheme to achieve the reliability for broadcasting. In our scheme, the safety messages are rebroadcast when the sender is solicited. This increases the percentage of vehicles receiving the messages while duplicated messages are limited. Secondly, with consideration of the fragmentation of the network, we study solutions that overcome the temporary disconnection in the network to bring the safety information to the recipients. Based on the social properties of vehicular networks, we propose a social-based forwarding protocol to support the communication between vehicles to points of interest that provide safety services with looser time constraints, such as search and rescue. Thirdly, we investigate jamming attack, a kind of DoS attacks, which is crucial for safety applications because of the adequate condition of the attack at the lower layers. We model jamming attack on broadcasting in order to study the degradation caused by the attack on network performance. The degradation at a certain level in network performance is an indication of a jamming attack presence in the network; therefore results from this analysis will allow us to determine network performance thresholds to distinguish between normal and attacked scenarios. However, according to our analysis, the method using the degradation as an indication to detect a jamming attack is not feasible for real-time applications. Hence, we propose methods to detect jamming attacks in real-time. Our methods allow real-time detection with high accuracy, not only at the central monitor but also at each vehicle. Therefore, vehicles are noticed about the attack soon enough to recover the communication and react to these attacks.