Abstract: In a（t，n） threshold proxy signature，any set of t members who present the original singer can issue a signature while any set of less than t members can not issue a signature at all.A secure（t，n） threshold proxy signature scheme is proposed aiming at conspiracy attack.That is：any t or more malicious proxy signatures may work together to reconstruct the secret keys of other members in proxy group，consequently they can impersonate some other proxy signers to generate a valid threshold proxy signature.The new scheme can not only satisfy the properties of the threshold proxy signature，but also withstand the conspiracy attack.

Key words: （t, n） threshold proxy signature, trusted party, conspiracy attack

摘要： 在一个（t，n）门限代理签名方案中，任何t个成员组成的集合可以代表原始签名人进行代理签名，而任何少于t个成员的集合都不能进行代理签名。针对合谋攻击提出了一个安全的（t，n）门限代理签名方案。合谋攻击是指在不知道任何有效的门限代理签名的情况下，恶意代理成员人数大于或等于门限值时，他们能合谋重新构造代理群的秘密参数，从而可以伪造其他代理成员的签名。新方案不仅能满足门限代理签名的性质，而且能抵抗合谋攻击。

关键词: （t, n）门限代理签名, 可信中心, 合谋攻击