Abstract: Recently, some researchers have been come up with some forward secure proxy signature schemes and some improved forward secure proxy signature schemes. By analyzing the security of the three proxy signature schemes points out that they are insecure and have not characteristic of forward security. When the proxy signer’s private key is leak, the original signer can forge the proxy signature even if he don’t know the key before session. The scheme can not resist the original signer’s forgery attack.

Key words: proxy signature, forward security, forgery attack

摘要： 针对最近一些学者提出的前向安全的代理签名方案以及改进的前向安全的代理签名方案，给出了三种代理签名方案的安全性分析，发现它们是不安全的，均不具有真正的前向安全性。当代理签名人的私钥泄漏以后，原始签名人不去计算以前时段的密钥，就可以伪造代理签名，方案不能抵抗原始签名人的伪造攻击。

关键词: 代理签名, 前向安全, 伪造攻击