The impact of security on cooperative awareness in VANET

Vehicular networking enables new safety applications that aim at improving roads safety. Because of their direct relation to driver's safety, this goal can only be achieved if vehicular networking is based on a technology that is robust against malicious attackers. Therefore, security mechanisms such as authentication are proposed. However, security comes at a cost in terms of computational and communication overhead. For example, a signature and certificate are appended to every beacon sent, which generates an extra load on the network. Moreover, most of the safety applications require a perfect awareness of the vehicle's surroundings to perform adequately. To represent such awareness, the Awareness Quality is used to indicate the current level of awareness of the vehicle. This metric was previously used by the Decentralized Congestion Control community to improve channel usage. In this paper, we use the Awareness Quality to investigate the impact of security on cooperative awareness in VANET. Then, we apply this metric to the mechanism of certificate omission, and provide extensive simulation results. The attributes of Awareness Quality metrics enable us to investigate the behavior of certificate omission schemes with a precision that was not provided by aggregate metrics. This enables us to show that congestion-based certificate omission with a quadratic adaption function is the most effective scheme among existing certificate omission schemes.