International Association
for Cryptologic Research

Secret handshakes (SH) scheme is a key agreement protocol between two members of the same group. Under this scheme two members share a common key if and only if they both belong to the same group. If the protocol fails none of the parties involved get any idea about the group affiliation of the other. Moreover if the transcript of communication is available to a third party, she/he does not get any information about the group affiliation of communicating parties. The concept of SH was given by Balfanz in 2003 who also gave a practical SH scheme using pairing based cryptography. The protocol proposed by Balfanz uses one time credential to insure that handshake protocol performed by the same party cannot be linked. Xu and Yung proposed SH scheme that achieve unlinkability with reusable credentials. In this paper, a new unlinkable secret handshakes scheme is presented. Our scheme is constructed from the ZSS signature and inspired on an identity based authenticated key agreement protocol, proposed by McCullagh et al. In recently proposed work most of unlinkable secret handshake schemes have either design flaw or security flaw, we proved the security of proposed scheme by assuming the intractability of the bilinear inverse Diffie-Hellman and k-CAA problems.