Abstract: Two attacks on Wang et al.’s threshold proxy signcryption scheme with shared verification show that their scheme are insecure.The one is that their scheme does not has the property of shared verification；the other is that their scheme cannot resist the attack of revising the warrant.Further，a modification to their threshold proxy signcryption scheme can satisfy the security requirement.

Key words: threshold proxy signcryption, shared verification, verification signcryption

摘要： 指出了王等的具有共享验证的门限代理签密方案存在两个安全性缺陷，一是该方案并不满足共享验证这一特性，二是代理组可修改授权证书。进一步，给出了改进方案，克服了原方案的缺陷。

关键词: 门限代理签密, 共享验证, 验证签密