关键词: 无证书签名, 代理签名, 公钥替换攻击, 恶意的KGC攻击, 双线性对

Abstract: This paper analyzes a certificateless proxy signature scheme and points out it are vulnerable against two types of adversaries in certificateless cryptosystems. Type I adversary can replace the user’ public key to forge proxy delegations from any original signer to any proxy signer and compute the proxy signature; type II adversary（KGC） can generate the trapdoor system parameters according to the identity information of a pre-selected target user and then forge the proxy delegations from the target user to other users. To overcome these security problems, a new improved proxy signature scheme is proposed. Analysis shows that the new scheme has better security.

Key words: certificateless signature, proxy signature, public key replacement attacks, malicious KGC attacks, bilinear mapping