On the security of a novel and efficient unlinkable secret handshakes scheme

Quite recently [IEEE Commu. Letters, Vol. 13, No. 5, 2009], Huang and Cao proposed a novel and efficient unlinkable secret handshakes scheme claiming to provide unlinkability and better performance than previously reported ones. In this paper, we will point out their scheme has a serious security loophole due to an inherent design flaw. Thus, we hope that by identifying the design flaw, similar mistakes can be avoided in future unlinkable secret handshakes designs.