关键词: 不可伪造性, 不可追踪性, 前向安全, 代理盲签名, 二次剩余困难问题

Abstract: Through the security analysis of a forward secure proxy blind signature scheme proposed by Xiao Hongguang et al., it is pointed out that the scheme doesn’t resist the original signer’s forgery attack, which means a dishonest original signer is able to forge the proxy signing key. Meanwhile, the scheme doesn’t satisfy the untraceability and forward security. To solve the above problems, an improved scheme is presented. By improving the method of the delegate authorization and the process of blind signature, the improved scheme overcomes the security problems existing in the former scheme. Then based on discrete logarithm problem and quadratic residue problem, the security properties of unforgeability, strong blindness and forward security are analyzed. The analysis results show that the improved scheme satisfies the security requirements of a forward secure proxy blind signature scheme.

Key words: unforgeability, untraceability, forward security, proxy blind signature, quadratic residue problem