Weakness of the Synchro-Difference LKH Scheme for Secure Multicast

Zhu proposed a synchro-difference LKH scheme for secure multicast that appeared in IEEE Communications Letters, vol. 9, no. 5, pp. 477-479, May 2005, which is an enhancement of the well-known LKH scheme. In this letter, we show that Zhu's scheme is insecure against collusion of two or more malicious adversaries by presenting two kinds of attack scenarios.