Comments on the Yang–Chang–Hwang anonymous conference key distribution system

Yang et al. [Comput. Stand. Interfaces 25 (2003)] proposed a conference key distribution system (CKDS) based on the elliptic curve discrete logarithm problem (ECDLP). Their scheme used a line with a hash value to broadcast the conference key. In this article, we point out that it suffers from the attack by solving linear equations to obtain the hash value hi. Thus, the conference key CK can be obtained by using the known parameter hi. We also propose an improved scheme to overcome the weakness.