CAPS: Context-Aware Privacy Scheme for VANET Safety Applications

Preserving location privacy in vehicular ad hoc networks (VANET) is an important requirement for public accep- tance of this emerging technology. Many privacy schemes concern changing pseudonyms periodically to avoid linking messages. However, the spatiotemporal information con- tained in beacons makes vehicles traceable and the driver’s privacy breached. Therefore, the pseudonym change should be performed in a mix-context to discontinue the spatial and temporal correlation of subsequent beacons. Such mix- context is commonly accomplished by using a silence period or in predetermined locations (e.g., mix-zone). In this pa- per, we propose a location privacy scheme that lets vehicles decide when to change its pseudonym and enter a silence period and when to exit from it adaptively based on its con- text. In this scheme, a vehicle monitors the surrounding vehicles and enters silence when it finds one or more neigh- bors silent. It resumes beaconing with a new pseudonym when its actual state is likely to be mixed with the state of a silent neighbor. We evaluate this scheme against a global multi-target tracking adversary using simulated and realistic vehicle traces and compare it with the random silent period scheme. Furthermore, we evaluate the quality of service of a forward collision warning safety application to ensure its applicability in safety applications. We measure the quality of service by estimating the probability of correctly identify- ing the fundamental factors of that application using Monte Carlo analysis