Abstract：Two kinds of forgery attacks strategy on the group signature schemes proposed respectively by Wang et al.. (2003) and Lin et al.. (2006) based on the Tseng-Jan’s(1999) group signature scheme is developed. Without using any secret identification or secret key, anyone can forgery a valid group member certificate and then generate a valid group signature using the forged certificate only through selecting some random parameters and changing the calculation procedures. Moreover, this kind of forgery attacks strategy can be used in Lee-Chang’s (1998) group signature scheme, Tseng-Jan’s group signature scheme and their varietals’. It means this series of group signature schemes is insecure.
2009, Vol. 31 
