Achieving Efficient Cooperative Message Authentication in Vehicular Ad Hoc Networks

Recently, vehicular ad hoc networks (VANETs) have emerged as a promising approach to increasing road safety and efficiency, as well as improving the driving experience. This can be accomplished in a variety of applications that involve communication between vehicles, such as warning other vehicles about emergency braking; however, if we do not take security and privacy issues into consideration, the attractive features of VANETs will inevitably result in higher risks for abuse, even before the wide deployment of such networks. While message authentication is a common tool for ensuring information reliability, namely, data integrity and authenticity, it faces a challenge in VANETs. When the number of messages that are received by a vehicle becomes large, traditional exhaustive (or per-message) authentication may generate unaffordable computational overhead on the vehicle and therefore bring unacceptable delay to time-critical applications, such as accident warning. In this paper, we propose an efficient cooperative authentication scheme for VANETs. To reduce the authentication overhead on individual vehicles and shorten the authentication delay, this scheme maximally eliminates redundant authentication efforts on the same message by different vehicles. To further resist various attacks, including free-riding attacks that are launched by selfish vehicles, and encourage cooperation, the scheme uses an evidence-token approach to controlling the authentication workload, without the direct involvement of a trusted authority (TA). When a vehicle passes a roadside unit (RSU), the vehicle obtains an evidence token from the TA via the RSU. This token reflects the contribution that the vehicle has made to cooperative authentication in the past, which enables the vehicle to proportionally benefit from other vehicles' authentication efforts in the future and thus reduce its own workload. Through extensive simulation, we evaluate the proposed cooperative authentication scheme in terms of workload savings and the ability to resist free-riding attacks.