Abstract: Through?the security analysis of?the proxy blind signature scheme which is proposed by Liu et al., it shows that security flaws exist in the scheme: a dishonest original signer can forge the proxy signing key, that is to say it doesn’t satisfy strong unforgeability; the proxy signer can make a linkage between the signature on original message and the signature on corresponding blind message, that is to say the scheme is linkable. An improved scheme is proposed to overcome these security problems. By modifying the?equation of?the delegate authorization and the process of blind signature, the new scheme can resist the original signer’s forgery attacks, and also has unlinkability.

Key words: proxy blind signature, discrete logarithm, unlinkability, forgery attack

摘要： 通过对柳等提出的代理盲签名方案进行安全性分析，指出方案存在以下安全缺陷：不诚实的原始签名人可以伪造代理签名密钥，即方案不满足强不可伪造性；代理签名人可以将盲消息的签名和原消息的签名联系起来，即方案是可链接的。针对这些安全缺陷，提出了一种改进的代理盲签名方案。通过修改代理授权方程和盲签名过程，新方案可以抵抗原始签名人的伪造攻击，且满足非关联性。

关键词: 代理盲签名, 离散对数, 非关联性, 伪造攻击