Intersections are Not Good for Your Privacy

Cooperative Awareness Messages (CAM) defined by ETSI Intelligent Transport Systems (ITS) can compromise privacy as a result of its transmission criteria. Because these transmission criteria reflect vehicle's movement, the resulting transmission patterns serve as metadata of vehicles. Passive observations of these patterns can help correlate with a specific vehicle on the road. Furthermore, in some cases, this correlation and identification of a vehicle is independent of the number of vehicles present in the vicinity. Observations from our simulation indicate that the mandatory use and occasional change of pseudonyms is a false premise as they do not protect privacy. In fact, the use of pseudonyms has no bearing with this context. Consequently, the existing CAM transmission criteria pose a tradeoff question between cooperative awareness (and ultimately road safety) and privacy. We propose that ETSI ITS standard to consider our findings and re-evaluate the CAM transmission criteria in Vehicule-to-Everything (V2X) communication.