A Weakness in Jung-Paeng-Kim's ID-based Conference Key Distribution Scheme

Very recently, Jung, Paeng and Kim [IEEE Communications Letters, Vol 8, No 7, pp 446–448, July 2004] have demonstrated the insecurity of Xu and Tilborg’s ID-based conference key distribution scheme, and in addition, have revised the scheme to fix the security flaws discovered by them. However, in this paper, we show that Jung-Paeng-Kim’s revised scheme is still insecure since it is vulnerable to an active attack of colluding adversaries. We also show that our attack can be easily thwarted by a simple patch.