Cryptanalysis of an Efficient Secret Handshakes Scheme with Unlinkability

In 2011, Gu-Xue proposed an improved secret handshakes scheme with unlinkability based on the Huang-Cao scheme that can achieve strong unlinkability against an outsider adversary. How- ever, this paper points out that Gu-Xue scheme is insecure to key-compromise impersonation (K-CI) attack and cannot provide master key forward secrecy (MFS).