一个无可信中心(t，n)门限签名方案的安全缺陷及其改进  

Security Analysis of the(t,n) Threshold Signature Scheme without a Trusted Party and Its Improvement

作　　者：张文芳[1] 王小敏[1] 何大可[1] 

机构地区：[1]西南交通大学信息科学与技术学院

出　　处：《铁道学报》2008年第3期40-45,共6页Journal of the China Railway Society

基　　金：西南交通大学青年教师科研起步项目(2007Q135)

摘　　要：针对王斌和李建华的无可信中心(t,n)门限签名方案(简称王-李方案),给出两种伪造签名攻击及相应的合谋攻击。指出由于王-李方案的联合秘密共享技术并没有起到实质性作用,且iλ,j是通过广播方式分发的,因此存在安全隐患。为克服王-李方案的上述缺陷,提出一个改进方案。改进方案将群成员的固有私钥ki与分布式生成的秘密份额iλ共同作为其部分签名私钥,然后利用(ki,iλ)的完整信息,在随机因子ti的作用下,联合生成部分签名和门限群签名,从而克服了王-李方案的签名方程参数退化问题,能够完全抵抗合谋攻击和伪造签名攻击。此外,改进方案还增加了对密钥影子的验证功能。分析表明,改进方案不仅具有更高的安全性,而且具有较高的效率。Two forgery attacks and their corresponding conspiracy attacks are proposed against the （t, n） threshold signature scheme without a trusted party worked out by Wang Bin and Li Jian-hua（the WL Scheme for short）. It is pointed out that serious insecurity dangers are hidden in the WL scheme and they are induced by incomplete execution of joint secret sharing technology and broadcasting of λi,j （i,j= 1,2,..., n; i≠j）. An improved scheme is presented to overcome the above defects of the WL scheme. In the improved scheme, each group member＇s partial signing key is composed of his original secret key kl and his combinatorial secret shadow λi, and his partial and threshold group signature is generated making use of full information of （ki ,λi） and random factor ti. In the above way, depletion of signature generation functions is elimited and conspiracy attacks and forgery attacks are resisted successfully, and further more verification of secret shadows is realized. Analysis shows that the improved scheme is of higher security and efficiency.

关 键 词：门限签名 联合秘密共享 合谋攻击 伪造签名攻击 可信中心 

分 类 号：TP309[自动化与计算机技术—计算机系统结构]