A security metric for VANET content delivery

Vehicular Ad-hoc Network (VANET) enables wireless communications among vehicles. VANET applications benefit to the society with improved transportation safety and efficiency. However, security issues in delivering contents over infrastructureless wireless communication hinder VANET applications. Though security schemes have been proposed, the public remains skeptical due to the lack of common metrics to measure their effectiveness. This paper proposes an asymmetric profit-loss Markov (APLM) model to measure the integrity level of security schemes for VANET content delivery. Profit defines integrity gain to a system by its devices detecting and disregarding corrupted data fragments. Loss represents negative effect to a system at receiving a corrupted data fragment. Markov chain records change of system behavior that reacts to profit and loss asymmetrically. The advantage of APLM model is its black-box approach that measures the integrity level without the need to examine the implementation details of a particular security scheme, rendering the model feasible for real world applications. Taking into account the special characteristics of integrity schemes in VANET, APLM model is tested on five scenarios. The measuring results demonstrate meaningfulness, repeatability, and feasibility of APLM model. APLM model also supports optimization of security scheme design for VANET content delivery.