We study privacy-preserving tests for proximity: Alice can test if she is close to Bob without either party revealing any other information about each other’s location. We describe several secure protocols that support private proximity testing at various levels of granularity. We introduce the concept of location tags generated from the physical environment in order to strengthen the security of proximity testing. We implemented our system on the Android platform and report on its effectiveness. Our system uses a social network (Facebook) to manage user public keys. We argue that for proximity testing, social networks are better suited for managing user keys than traditional PKI.