Privacy preserving proximity testing using elliptic curves

Abstract

The availability of GPS in smartphones and other wireless devices has made location based services extremely popular. One of the most widely used location based services is finding nearby friends. Popular social networks like Facebook offer this service purely based on exact user locations. To subscribe to this feature, users are forced to let the service provider know their actual locations, compromising their location privacy. In this paper, we present a protocol based on elliptic curve cryptography concepts for proximity testing which can preserve location privacy of the users. Our protocol enables two parties, Alice and Bob, to test whether they are within an agreed upon distance range from each other without revealing their exact location. Our security analysis shows that our protocol is secure against most known location privacy threats including location triangulation attacks. From experimental evaluation performed on prototype implementation, we found that our protocol is practical for resource-constrained smartphone devices requiring a reasonably small execution time (53 ms) without the communication overhead.