中文摘要：

该文分析了Seo等（2003）和黄振杰等学者（2004）提出的两个提名代理签名方案,指出这两个方案都不具备强不可伪造性。分别给出了一种伪造攻击,利用这种攻击,一个不诚实的原始签名人通过设置特定的参数,可以成功伪造代理签名密钥,从而可以假冒诚实的代理签名人生成有效的提名代理签名,威胁到代理签名人的合法权益。

英文摘要：

Analyses of two nominative proxy signature schemes proposed by Seo et al. （2003） and Huang et al. （2004） are given in this paper. The results show that neither the scheme has the property of strong unforgeability. A forgery attack on the two schemes is given, respectively. Using the forgery attack, a dishonest original signer can forge a proxy signing key on behalf of the designated proxy signer by assigning some parameters and produce valid nominative proxy signatures, which does harm to the benefits of the proxy signers.