Abstract: In this paper,through the cryptanalysis of Dai et al. designated-receiver proxy signature scheme and Xue et al. threshold proxy signature scheme using self-certified public keys,it is found that these schemes were both insecure against the forgery attack.To eliminate the weakness of two schemes,improved schemes which satisfy the required secure properties of the proxy signature are proposed,respectively.

Key words: proxy signature, forgery attack, security analysis, threshold signature, designated-receiver signature

摘要： 对Dai等人的指定接收人的代理签名方案和Xue等人的采用自我认证公钥的门限代理签名方案进行了密码分析,发现它们是不安全的,都不能抵抗伪造攻击。针对这两个方案的缺陷,对其进行了改进,改进后的方案满足了代理签名的安全性要求。

关键词: 代理签名, 伪造攻击, 安全分析, 门限签名, 指定接收人签名