The success of online social networking and of mobile phone services
has resulted in increased attention to mobile social networking.
Matchmaking is a key component of mobile social networking.  It 
notifies users of nearby people who fulfil some criteria, such as
having shared interests, and who are therefore good candidates for
being added to a user's social network.  Unfortunately, the existing
matchmaking approaches are troublesome from a privacy point of view.
One approach has users' smartphones broadcast their owners' personal
information to nearby devices.  This approach reveals more personal
information than necessary.  The other approach requires a trusted
server that participates in each matchmaking operation.  Namely, the
server knows the interests and current location of each user and
performs matchmaking based on this information.  This approach allows
the server to track users. 

This paper proposes a privacy-preserving matchmaking protocol for
mobile social networking that lets a potentially malicious user learn
only the interests (or some other traits) that he has in common with a
nearby user, but no other interests.  In addition, the protocol is
distributed and does not require a trusted server that can track users
or that needs to be involved in each matchmaking operation.  We
present an implementation and evaluation of our protocol on Nexus One
smartphones and demonstrate that the protocol is practical.