Protecting the privacy of location data using the openPDS-SafeAnswers framework -

Abstract

Billions of applications have already been downloaded by smartphone users. To successfully download an application, the application asks the user to accept a set of permissions allowing it to access sensitive information on the phone. It is mostly unclear when such data is being accessed, how it is being used, and for what purposes. A framework called openPDS, was recently suggested to limit such privacy invasion. openPDS gives the user full control over her data and only allows access to the data-metadata via safe answers. Although openPDS protects the user’s raw data, sensitive personal information, such as location trace, can still be inferred by the service provider by analyzing the accumulated answers. In this work, we focus on location privacy and append openPDS with a module that prevents the service provider from reconstructing the trace of users. The module might provide a correct answer, a wrong one, or might not answer at all. However, the module guarantees quality of service (QoS) by abiding with the QoS requirements necessitated by the provider, which we define as the tolerance of the application to inaccurate answers. We tested our approach on 10 users whose locations traces were recorded for 10 months. The results show that no user trace was successfully reconstructed even when high QoS levels were required. Moreover, the adversary knowledge gained through the recurrent months was not maintained.