  Private handshaking allows pairs of users to determine which (secret) groups
they are both a member of. Group membership is kept secret to everybody else.
Private handshaking is a more private form of secret handshaking, because it
does not allow the group administrator to trace users. We extend the original
definition of a handshaking protocol to allow and test for membership of
multiple groups simultaneously. We present simple and efficient protocols for
both the single group and multiple group membership case.
  Private handshaking is a useful tool for mutual authentication, demanded by
many pervasive applications (including RFID) for privacy. Our implementations
are efficient enough to support such usually resource constrained scenarios.

Cryptography and Security