中文摘要：

群签名允许每个成员代表整个群体作出签名，它是构造电子现金、电子拍卖、电子选举方案的基本工具．本文通过极其简单的攻击方法证明Zhang et al在2003年和Kim et al在1996年提出的两个群签名方案是不可追踪的．与Wang et al提供的攻击方法相比，本文所发展的技巧十分新奇有趣．

英文摘要：

Group signature allows individual members to make signatures on behalf of the whole group. It can be used to constitute a very useful basic tool in many settings, such as E-cash, E-auction and E- election. In this paper, by very simple attacks we show that the two group signatures proposed by Zhang et al in 2003 and Kim et al in 1996 are untraceable. In contrast to those attacks presented by Wang et al, the techniques developed in this paper are novel and interesting.