中文摘要：

分析了一种基于离散对数的群签名方案，通过合理选择相关的群签名参数，在成员证书和签名密钥未知时使群签名方案的验证等式通过，从而证明了原方案可以被完全攻破，也就是说原方案不能抵抗伪造攻击．给出了原方案的3种伪造攻击方法．同时也证明了原方案不具备防陷害性，即只要攻击者拥有合法签名者的1个签名，就可以以这个签名者的身份对任何消息进行签名，当签名被打开时只能追踪到这个合法的群成员，致使合法群成员被陷害．从而说明了原方案是不安全的．

英文摘要：

Analysis of a group signature scheme based on a discrete logarithm shows its weakness in the area of unforgeability and proves that this scheme is vulnerable to attack. When group member＇s certificates and secret keys for signatures are unknown, an attacker could pass verification by choosing appropriate parameters for group signa- tures. Three attack modes against the original scheme are given. In this paper, we show that the original scheme was incapable of defending against circumvention, which means that any attacker could disguise themselves as a legal group member. This means they could sign any message they wanted once the attacker derived a signature of a group member. When the signature was opened by the group manager, the legal group member would be identified. Thus the legal member would be held responsible for the attacker＇s fraudulent message. The scheme is not secure.