Abstract: Analysis of Zhang-Mao’s id-based designated verifier signature shows that non-designated-verifier can also check the validity of the signature.In this paper，an improvement scheme is proposed，which not only overcomes the disadvantage but also retains the merits of the original id-based designated verifier signaturescheme.Analysis of Kang et al’s id-based designated verifier signature shows that it does not have unforgeability.The improved scheme mends the security leak of it and also retains the merits of the original signature scheme.

Key words: designated verifier signature, identity-based, bilinear pairings

摘要： 分析Zhang-Mao的基于身份指定验证者签名后发现非指定验证者也可以验证签名的有效性，对其进行了改进，改进后的方案克服了原方案的不足，并且保留了原方案的其他优点。分析Kang等人的基于身份指定验证者签名后发现其方案并不具有不可伪造性，改进后的方案在保留原方案优点的同时克服了原方案的安全隐患。

关键词: 指定验证者签名, 基于身份, 双线性对