“…To protect users' location privacy during usage of location based services (LBS), various location privacy protection mechanisms have been proposed. Based on their core ideas, these mechanisms can be broadly categorized into approaches that use dummies [29,32], space transformation [18,28], mix-zone [6,36], encryption [31], spatial cloaking [5,10,17,20,21,27,30,34,40,43] and differential privacy [3,22,42]. The basic ideas behind these techniques are briefly discussed as follows.…”