Anonymity Analysis on Social Spot Based Pseudonym Changing for Location Privacy in VANETs

Location privacy is one of the Quality of Privacies (QoP) in vehicular ad hoc network (VANET) and imperative for the VANET's full flourish. Frequent pseudonym changing can provide a promising solution to achieve location privacy, however if the pseudonyms are changed in an improper occasion, the solution is ineffective. In this paper, to improve the effectiveness of this kind of solution, we first introduce the social spot where many vehicles could aggregate, e.g., a road intersection when the traffic light is red or a free parking lot near a shopping mall. We then propose a social spot based pseudonyms changing technique to achieve the location privacy. By taking the anonymity set size as the privacy metric, we develop two anonymity analytic models to quantitatively investigate the location privacy achieved in the technique. The analytical results show that better location privacy can be achieved when a vehicle changes its pseudonyms at some highly social spots, and as a result, the proposed models can be used to assist vehicles to change their pseudonyms for better location privacy at the right moment and place.