Unlinkable Secret Handshakes from MessageRecovery Signature

Secret handshake scheme allows the membersof a certain organization can anonymously authenticateeach other. In this paper, two Unlinkable secret handshakeschemes (called USH-1 and USH-2) are proposedby using the Message recovery signature (MRS). USH-1 achieves the unlinkability with one-time pseudonyms,whilst USH-2 obtains a strong unlinkability against groupauthority with reusable credentials. The security of USH-1 and USH-2 are reduced to the intractability of DiscreteLogarithm Problem and the k + 1 Square Roots Problem,respectively. Compared with some seminal schemes, bothof our schemes are competitive in the performance.