Trusted Location Based Services

There are currently numerous smartphone-based applications that utilize the users' current positions to provide Location Based Services (LBS). In all of these applications it is in the interest of the user to submit as-accurate-as-possible position information in order to get the best of the service. However, there is yet hardly any service, which requires the user to prove that she is at a specific location at a certain point in time. The reason for the lack of such services lies in the fact that none of the position and time information gained by nowadays smartphones is trustworthy. In order to address this problem, this paper investigates the issues with the current systems and analyzes the basic requirements for trusted location information. Based on these results, we propose a smartphone-based solution relying on trusted third parties and qualified electronic signatures, which allows users to prove their current locations. The applicability of our solution is illustrated by means of two prototype implementations. Finally, the security of our solution and of the developed prototypes is assessed by a detailed security and risk analysis.