关键词: 离散对数, 代理盲签名, 密码分析

Abstract: This paper presents a security analysis of two DLP-based proxy blind signature schemes proposed recently by Gao et al and Yu et al respectively and point out that both of the two schemes are insecure against the proxy signer’s linkability attacks as well as the user’s forgery attacks.Gao et al’s scheme is an improved scheme of Tan et al’s.However，it is still vulnerable to the proxy signer’s linkability attacks.Yu et al’s scheme is also insecure against the proxy signer’s linkability attacks.In addition，the user can deduce the proxy signature private key by using a valid proxy signature，and then instead of the proxy signer he can forge a valid proxy signature of a message m.He also can directly forge a valid proxy signature which related to the valid signature received from the proxy signer.This paper presents an improved scheme that can against the proxy signer’s linkability attacks.

Key words: discrete logarithm problem, proxy blind signature, cryptanalysis