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, a dynamic location obfuscation mechanism proposed by Yu, Liu and Pu (NDSS 2017), and show that PIVE fails to offer either of the privacy guarantees on adaptive Protection Location Sets (PLSs) as claimed. Specifically, we demonstrate that different PLSs could intersect with one another due to the defined search algorithm, and then different apriori locations in the same PLS could have different protection diameters. As a result, we can show that the proof of local differential privacy for PIVE is problematic. Besides, the condition introduced in PIVE is confirmed to be not sufficient for bounding expected inference errors in general, which makes the user-defined inference error threshold invalid. To address these issues, we propose a couple of correction approaches, analyze theoretically their satisfied privacy characteristics and detail their respective merits and demerits.

翻译：不同隐私(不可区分性)和扭曲隐私(推定错误)的共同保障限制了信息泄漏。在本文中,我们分析了由刘刘 ⁇ 和浦提出的动态位置模糊机制(NDSS 2017)的PIVE的隐私差异,并表明PIVE未能提供所声称的适应性保护地点(PLS)的隐私保障。具体地说,我们证明不同的PLS可能由于界定的搜索算法而相互交叉,而同一PLS的不同优先地点可能具有不同的保护直径。因此,我们可以证明当地对PIVE的隐私差异的证据存在问题。此外,PIVE采用的条件被证实不足以约束一般预期的推断错误,这使得用户定义的推断错误阈值无效。为了解决这些问题,我们建议了几种纠正方法,从理论上分析其满足的隐私特征,并详细说明其各自的优点和缺点。