Global privacy and transportation mode homogeneity anonymization in location based mobile systems with continuous queries

A major concern for deployment of location-based mobile systems is the ill-usage of mobile client's location data, which may imply sensitive and private personal information. Also, even if the location is exposed willingly by the mobile client the query should not be linked to the mobile client. Still, many location based systems (store finders, transit itinerary systems, and social networks) are created with a different focus and have little concern for end user privacy. We focused on location based mobile systems where the location of the mobile user may be available; however, an adversary should not be able to link a query to a specific mobile user. Two key contributions of this work are the introduction and experimental evaluation of a novel concept called transportation mode homogeneity anonymization that adds another dimension to privacy in mobile location based systems. Also, a novel dynamic layered approach on achieving K-anonymity by separating the local privacy requirement on each snapshot and global privacy requirement across snapshots with different privacy goals is proposed to exploit the local privacy anonymization group as candidates to obtain global anonymization group candidates.