Privacy-preserving Verifiable Proximity Test for Location-based Services

The prevalence of smartphones with geo-positioning functionalities gives rise to a variety of location-based services (LBSs). Proximity test, an important branch of location-based services, enables the LBS users to determine whether they are in a close proximity with their friends, which can be extended to numerous applications in location-based mobile social networks. Unfortunately, serious security and privacy issues may occur in the current solutions to proximity test. On the one hand, users' private location information is usually revealed to the LBS server and other users, which may lead to physical attacks to users. On the other hand, the correctness of proximity test computation results from LBS server cannot be verified in the existing schemes and thus the creditability of LBS is greatly reduced. Besides, privacy should be defined by user him/herself, not the LBS server. In this paper, we propose a privacy-preserving verifiable proximity test for location-based services. Our scheme enables LBS users to verify the correctness of proximity test results from LBS server without revealing their location information. We show the security, efficiency, and feasibility of our proposed scheme through detailed performance evaluation.