Regionalized location obfuscation mechanism with personalized privacy levels.

Global Positioning Systems are now a standard module in mobile devices, and their ubiquity is fueling rapid growth of location-based services (LBSs). This poses the risk of location privacy disclosure. Effective location privacy preservation is foremost for various mobile applications. Recently two strong privacy notions, geo-indistinguishability and expected inference error, are proposed based on statistical quantification. They are complementary for limiting the leakage of location information. In this paper, we continue to study the differential privacy preservation of location obfuscation mechanism based on PIVE framework proposed by Yu, Liu and Pu on ISOC Network and Distributed System Security Symposium (NDSS) in 2017. Since PIVE fails to offer differential privacy guarantees on adaptive protection location set (PLS) as claimed, we develop DPIVE, a regionalized location obfuscation mechanism with two phases. In Phase I, we determine disjoint sets by partitioning all possible positions such that different locations in the same set share the common PLS. In Phase II, we construct a probability distribution matrix by exponential mechanism in which each row has its own sensitivity of utility (diameter of PLS).This approach utilizes the relationship between two privacy notions based on the user-defined inference error threshold and the prior knowledge about user's location. Moreover, we introduce PDPIVE, a personalized privacy framework, to achieve that each location has its own privacy level on two privacy control knobs, minimum inference error and differential privacy parameter. Experiments with two public datasets demonstrate that our mechanisms have the superior performance typically on skewed locations.