【作者】 朱南希；

【导师】 李志斌；

【作者基本信息】 华东师范大学 ， 计算机应用技术， 2007， 硕士

【摘要】 随着信息技术的迅速发展，我们已步入信息社会，计算机网络也成为社会赖以生存的基础．当前，计算机网络的安全问题日益突出，信息的安全保密和防伪问题成为人们关注的重要课题。在计算机安全技术的研究中，数字签名是解决信息安全问题的关键技术，其应用已渗透到电子商务、电子政务等众多领域．数字签名是对传统手写签名的模拟，其概念由Diffie和Hellman于1976年最先提出．而多重签名是一种面向团体的特殊数字签名，签名过程有多人参与，主要可分为有序签名方式和广播签名方式．目前提出的多重签名方案大都采用这两种方式之一，缺少两种方式的结合，不能满足实际应用中复杂的签名顺序．近年提出的结构化多重数字签名把有序和广播两种签名方式有效的结合起来，使得签名顺序结构化，从而允许方案采用更为随意和复杂的顺序进行签名．但已有的结构化多重签名方案较少且都存在一些不足之处，尤其是实际应用中的安全和效率问题．因此，如何设计一个安全高效的结构化多重签名方案在实际应用中有很大的研究价值．本文从数字签名的基础理论和实现技术出发，研究和分析了数字签名方案基于的三种主要公钥密码体制和几个典型签名方案，并对多重签名和结构化多重签名的研究现状进行了介绍．随后，本文分析了近年提出的几类结构化多重签名方案，着重探讨了基于ElGamal体制的结构化多重签名，指出方案中存在的内部成员串通进行欺诈抵赖的不安全情况，并给出一个改进方案，通过增加时间戳和可信赖的签名管理中心改善了原方案的安全性，同时，把原方案的两层签名结构扩展为多层结构，使得改进方案更具通用性，适用于各种复杂的签名结构．考虑到方案的实用性，本文还对改进方案涉及的关键算法进行了深入的研究，探讨了参数的选取规则以及各主要算法的原理和实现(包括大随机数生成、素数判定、生成元求解和大整数模运算)，并分析了各算法的效率．更多还原

【Abstract】 With the rapid development of information technology, we have already stepped into the information society and the computer network has become the foundation we live by. Because of the more and more severe security problems of computer network, how to keep information secret and to avoid forgery is becoming a subject that people pay much attention to. Among the computer security technologies, digital signature, which has been applied to many fields such as electronic business and electronic government affairs, is a key method to solve the information security problems.Digital signature, first proposed by Diffie and Hellman in 1976, is the analog of traditional handwritten signature. Multi-signature is a special signature oriented to groups, which involves more than one person in the signing process. The signing order can be divided into two kinds: sequential and broadcasting. Most proposed multi-signature schemes follow one of the above signing orders and lack the mixture of both two, which cannot satisfy the complicated signing order in practical applications.Recently the structured multi-signature has been proposed to combine both sequential and broadcasting orders together effectively. The signing order becomes structured so that signers can sign in a more flexible and complicated order. However, there are few structured multi-signature schemes having been raised up and the existing ones all have some deficiency, especially security and efficiency in practical applications. So how to design a secure and efficient structured multi-signature scheme is of great value in research.Beginning with the basic theory and implementing technology of digital signature, the thesis analyzes the three public-key cryptosystems on which digital signature mainly bases and discusses some typical signature schemes. The status quo of researches on multi-signature and structured multi-signature is introduced subsequently. Several structured multi-signature schemes proposed recently are analyzed in the thesis and the discussion is focused on the ElGamal based schemes. The thesis points out the insecure cases in the original scheme such as conspiracyof inner members to cheat or deny and presents an improved scheme to solve these problems by adding a reliable signature-center and a time-stamp. Besides, the two-level signing structure in the original scheme is extended to multi-level structure so that the improved scheme can apply to all kinds of complicated signing structures and become more generalized.Considering the practicality, the thesis also discusses and implements the central algorithms involved in the improved scheme including choosing parameters, generating big random numbers, determining prime numbers, calculating primitive element and the module operations of big integers. In addition, the executing efficiency of the above algorithms is analyzed in the thesis.更多还原