document: Supporting anonymous location queries in mobile environments with privacygrid This paper presents PrivacyGrid - a framework for supporting anonymous location-based queries in mobile information delivery systems . The PrivacyGrid framework offers three unique capabilities . First , it provides a location privacy protection preference profile model , called location P3P , which allows mobile users to explicitly define their preferred location privacy requirements in terms of both location hiding measures ( e.g. , location k-anonymity and location l-diversity ) and location service quality measures ( e.g. , maximum spatial resolution and maximum temporal resolution ) . Second , it provides fast and effective location cloaking algorithms for location k-anonymity and location l-diversity in a mobile environment . We develop dynamic bottom-up and top-down grid cloaking algorithms with the goal of achieving high anonymization success rate and efficiency in terms of both time complexity and maintenance cost . A hybrid approach that carefully combines the strengths of both bottom-up and top-down cloaking approaches to further reduce the average anonymization time is also developed . Last but not the least , PrivacyGrid incorporates temporal cloaking into the location cloaking process to further increase the success rate of location anonymization . We also discuss PrivacyGrid mechanisms for supporting anonymous location queries . Experimental evaluation shows that the PrivacyGrid approach can provide close to optimal location k-anonymity as defined by per user location P3P without introducing significant performance penalties .
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