Abstract: This paper presents a security analysis of Gao et al’s [(t,n)] threshold signature scheme without trusted party, which can not resist outward attack and public-key attack. Besides, it also improves Gao et al’s scheme and proposes a new [(t,n)] threshold signature scheme. The improved scheme doesn’t need a trusted center, its key generation only runs an interactive protocol among all the participants, and overcomes the original scheme’s weakness. The results prove it is secure and effective.

Key words: digital signature, threshold signature, without trusted party, outward attack, public-key substitute attack

摘要： 通过对高炜等人的无可信中心的[(t,n)]门限签名方案进行分析，发现该方案不能抵抗外部攻击和公钥替换攻击。在原方案的基础上提出了一个改进的[(t,n)]门限签名方案，不需要可信中心，密钥生成只需成员之间协商完成，从而弥补了原方案的不足之处。实验结果证明，改进后的方案是安全且高效的。

关键词: 数字签名, 门限签名, 无可信中心, 外部攻击, 公钥替换攻击