Cryptanalysis of Two Nominative Proxy Signature Schemes
对两个提名代理签名方案的密码学分析

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.