指名签名与指名代理签名

该文分别对一个指名签名方案(KPW方案)和一个指名代理签名方案(PL方案)进行分析，结果表明:在KPW方案中签名人不仅能验证而且也能向第三方证明签名的有效性，甚至能将签名转化为通常的自认证签名，因此不是指名签名方案；在PL方案中任何人都可验证签名的有效性，它只是一个自认证签名方案。该文进一步给出了KPW方案的一个改进方案，使之具有指名签名的全部性质，同时也给出了一个基于该方案的指名代理签名方案。

Nominative Signature and Nominative Proxy Signature

Analyses of a nominative signature scheme (KPW scheme) and a nominative proxy signature scheme (PL scheme) are given, respectively. The results show that the KPW scheme is not a nominative signature scheme since the nominator not only can verify and prove the validity of given signatures but also can convert given signatures into universally verifiable signatures, and that the PL scheme is only a self-authentication signature scheme since anyone can verify the validity of given signatures. Furthermore, an improvement of the KPW scheme, in which all properties of the nominative signature are held, and a nominative proxy signature scheme based on the proposed nominative signature scheme are proposed.