Light security scheme for Cooperative, Connected and Automated Mobility

Cooperative, Connected and Automated Mobility (CCAM) is a new paradigm adopted by academia and industry in order to provide safe, secure and sustainable mobility on all kinds of roads (highways, urban and rural roads). CCAM takes advantage of Cooperative Intelligent Transport Systems (C-ITS) to improve safety and to reduce traffic congestion thanks to communication and cooperation among all relevant actors (vehicle, road infrastructure, pedestrians, etc.). In Europe and the USA, adapted communication protocols have been proposed to ensure cooperation through the exchange of specific messages. In this study, we focus on the European protocols, particularly the Cooperative Awareness Messages (CAMs) as defined by the European Telecommunications Standards Institute (ETSI). CAMs are composed of a payload containing information about the vehicle status (speed, location, heading, etc.) and additional security information. This information includes a Pseudonym Certificate (PC) and a signature to guarantee the sender's authentication. However, since CAMs are sent periodically by vehicles at frequencies from 1 to 10 Hz, this addition of security data to the payload significantly increases the load and bandwidth of the communication channel. Instead of exhaustive authentication, we propose a new approach that allows vehicles to authenticate each other for the first time when they meet. Once this level of trust is reached, vehicles stop sending authenticated messages during a variable period of time (called a trust period). In addition, we propose a trust verification process to avoid malicious activities during this trust period. Our approach significantly reduces the number of signed sent CAMs, the verification and signature computations, leading to reduce communication overhead. Simulation tests conducted over the OMNET + + platform demonstrate that our approach leads to a significant decrease in communication overhead, reducing the volume of CAMs exchanged by 56%.