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How well can your car be tracked: Analysis of the European C-ITS pseudonym scheme

The change of pseudonym certificates for message authentication is the standard approach for privacy-friendly V2X communication. It’s crucial to use an effective and robust pseudonym changing scheme as the location privacy of vehicles relies strongly on it. Therefore, in this work we analyzed a pseudonym change strategy that is recommended by the European C-ITS platform and has good chances to be included in a future European standard. By simulating a realistic urban traffic scenario within Luxembourg, applying and attacking the pseudonym change strategy, we could evaluate the effectiveness of the scheme. Overall, linking pseudonyms with simple traffic statistics in a realistic city traffic scenario is more challenging than related work suggests. However, the consideration of additional static information from the V2X communication, such as length and width of the vehicle, enormously improves the linking of pseudonyms, and thus enables tracking of vehicles and generation of motion profiles. The level of location privacy is thereby particularly influenced by the number of vehicles in the vicinity and especially their properties, as well as, of course, by the observation capabilities of the attacker. Our results suggest that the introduction of VANETs, even with the C-ITS pseudonym scheme, enables the tracking of vehicles, and thus will decrease location privacy in the future.