该文认为该方案是全局可伪造的，群管理员可以对任何消息假冒任何成员生成有效的群签名。

This paper shows that Chen - Zhu's scheme is universally forgeable, that is, the group authority can forge a valid group signature on an arbitrary message, which stands in any group member.

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同时，也指出了另外一个缺陷即攻击者可以假冒原始签名人将任何消息的代理签名权委托给任何代理人。

It is pointed out that they have the same defect in security which is the attacker can forge an effective signer to actualize an attack of public key replace.

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该文给出的一种攻击方案表明他们的方案是不安全的，任何代理签名的接收者都可以假冒代理人对任意的消息生成有效的签名。

However, their scheme is insecure by presenting a forgery attack, any receiver can impersonate the proxy signer to sign any message without holding the responsibility.

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