On the Formation of Historically k-Anonymous Anonymity Sets in a Continuous LBS

Privacy preservation in location based services (LBS) has received extensive attention in recent years. One of the less explored problems in this domain is associated with services that rely on continuous updates from the mobile object. Cloaking algorithms designed to hide user locations in single requests perform poorly in this scenario. The historical k-anonymity property is therefore enforced to ensure that all cloaking regions include at least k objects in common. However, the mobility of the objects can easily render increasingly bigger cloaking regions and degrade the quality of service. To this effect, this paper presents an algorithm to efficiently enforce historical k-anonymity by partitioning of an object’s cloaking region. We further enforce some degree of directional similarity in the k common peers in order to prevent an excessive expansion of the cloaking region.