Abstract: Proxy signature allows an original signer to delegate his/her signing power to a proxy signer such that the proxy signer can sign messages on behalf of the original signer. Blind signature allows a user to have a given message signed by the signer without revealing any information about the message. Zhao et al recently proposes a proxy blind signature on the combination of the proxy signature and blind signature. However, this paper shows that the proposed scheme suffers with a universal forgery attack, original signer’s forgery attack and message owner’s forgery attack. This paper proposes an improved scheme that can avoid original signer’s and message owner’s forgery attack effectively and efficiently.

Key words: Proxy signature, Blind signature, Proxy blind signature, Security analysis

摘要： 代理签名是指原始签名人将签名权力委托给代理签名人，由代理签名人代表原始签名人对消息进行签名。盲签名是指签名人不知道所签消息的具体内容。Zhao和Liu结合代理签名和盲签名的特性提出了一种代理盲签名，该文指出Zhao和Liu提出的代理盲签名方案存在广泛的伪造攻击、原始签名人的伪造攻击和消息拥有者的伪造攻击等安全缺陷，并提出了改进的方案，改进后的方案可以有效地避免原始签名人和消息拥有者的伪造攻击。

关键词: 代理签名, 盲签名, 代理盲签名, 安全分析