Nominative Signature and Nominative Proxy Signature
指名签名与指名代理签名

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.