Location Privacy Via Private Proximity Testing
The authors study privacy-preserving tests for proximity: Alice can test if she is close to Bob without either party revealing any other information about their location. They describe several secure protocols that support private proximity testing at various levels of granularity. They study the use of "Location tags" generated from the physical environment in order to strengthen the security of proximity testing. They implemented their system on the Android platform and report on its effectiveness. Their system uses a social network (Facebook) to manage user public keys.