  Geo-indistinguishability and expected inference error are two complementary
notions for location privacy. The joint guarantee of differential privacy
(indistinguishability) and distortion privacy (inference error) limits the
information leakage. In this paper, we analyze the differential privacy of PIVE
dynamic location obfuscation mechanism proposed by Yu, Liu and Pu (ISOC Network
and Distributed System Security Symposium, 2017) and show that PIVE fails to
offer differential privacy guarantees on adaptive protection location set as
claimed. Specifically, we demonstrate that different protection location sets
could intersect with one another due to the defined search algorithm and then
different locations in the same protection location set could have different
protection diameters. As a result, we can show that the proof of differential
privacy for PIVE is incorrect. We also make some detailed discussions on
feasible privacy frameworks with achieving personalized error bounds.
