关键词: 代理签名, 前向安全, 无证书签名, 合谋攻击, 公钥替换

Abstract: The existed forward secure proxy signature schemes have some security faults more or less. This paper analyzes the security of a forward secure proxy signature scheme proposed by Chen Ningyu et al. The analysis result shows that the scheme cannot satisfy the forward security, cannot resist the collusion attack of PKG and the proxy signer, the attack of public key substituted and the forgery attack of the distrusted PKG. To get over the faults of Chen Ningyu’s scheme, an improved forward secure proxy signature scheme is proposed in this paper. The improved scheme satisfies all the security requirements of forward secure proxy signature scheme, moreover, it can resist the collusion attack, the distrusted PKG’s forgery attack and the public key substituted attack.

Key words: proxy signature, forward secure, certificateless signature, collusion attack, public key substituted