Summary
Cooperative Intelligent Transportation System (CâITS) is a growing research field since it improves traffic safety and efficiency. However, the security of CâITS messages is an important issue to deal with. This paper proposes a costâefficient solution that can help in the deployment of CâITS. The idea herein presented is to introduce trusted road operator vehicles (ROVs), to provide certificates for other vehicles when needed. These certificates, which are generally provided by roadside units (RSUs), are mandatory for the security and the anonymity of the communication. The main objective of this work is to help in enhancing the security of CâITS by allowing connected vehicles to download the needed certificates without using a physical fixed infrastructure of RSUs. The latter cannot be, in fact, widely deployed due to their high cost. The alternative herein proposed is to delegate the task of providing certificates to some trusted vehicles, namely, ROVs, which are in all the cases moving around the city to ensure some assigned missions. A mathematical model, considering both ROVs and RSUs, is proposed to quantify the effects of introducing ROVs on the probability of downloading certificates. The results show that ROVs almost double the communication probability between the vehicles and the certificate providers from 40.1% to 78.7% on a highway with a high traffic density. The higher the communication probability, the easier downloading certificates is. Moreover, realistic simulations are conducted using Simulation of Urban Mobility (SUMO) traffic simulator together with Network Simulator 3 (NS3) network simulator to show the efficiency of our proposal. The simulation results demonstrate a significant enhancement in the number of downloaded certificates and the number of exchanged messages, even when a few numbers of ROVs are introduced.