【作者】 邓长兵；

【导师】 徐兰芳；

【作者基本信息】 华中科技大学 ， 信息安全， 2007， 硕士

【摘要】 随着网络发展和信息系统的广泛使用,电子政务、电子商务甚至日常生活都要求对数字文件进行各种处理。数字签名作为手写签名在数字文件中的合法对应物必将被广泛应用。1996年Mambo,Usudu和Okamoto首先提出并系统阐述了代理签名的概念,在原始签名人与代理签名人具有法律效力的协议之下,代理签名人可代替原始签名人对文件进行签署。代理签名作为一种特殊的数字签名,在电子商务、电子选举、移动代理等方面有着重要应用,但是存在代理者身份保护、签名内容保密等匿名性问题,国内外学者围绕代理签名的匿名性问题展开了广泛研究。通过分析现有匿名代理签名方案的不足和漏洞,给出了三个改进方案。改进方案克服了原有方案中的缺陷,具有更高的安全性。另外,结合椭圆曲线密钥短、安全强度高的特性,给出了一个基于椭圆曲线密码的匿名代理签名方案,该方案较之基于离散对数问题的签名方案具有更高的安全性。需可信第三方的匿名代理签名方案和无可信第三方的匿名代理签名方案都是基于代理者身份保护的匿名代理签名方案,并都存在一定的不足或漏洞,比如原始签名者的伪造攻击、公钥替换攻击等。针对无可信第三方的匿名代理签名方案的不足,给出了一种安全性更高的改进方案,该方案能克服上述攻击漏洞,满足基于代理者身份保护的匿名代理签名的安全性要求。签名内容保密的匿名代理签名方案存在指定接收者的伪造攻击和代理者的权限滥用缺陷,给出的两个改进匿名代理签名方案能克服上述攻击漏洞,并证明了满足基于签名内容保密的匿名代理签名的安全性要求。更多还原

【Abstract】 With the development of networks and the wide application of information system, there are increasing demands on processing various digital documents in systems of E-Government and E-Commerce. Being a legal replacement for handwritten signatures, digital signature is sure to be more extensively used in the coming years. In 1996, Mambo, Usudu and Okamoto firstly proposed and systematically expounded the concept of proxy signature. If the original signer and the proxy signer have the protocal with the law efficacity, the proxy signer may substitute the original signer to sign the file. As a special digital signature, proxy signature has many important applications in E-commerce, E-elections and mobile agents etc. But there exist some anonymous problems, such as the protection of proxy signer’s privacy and the confidentiality of content and so on, which arouse extensive research.After analyzing the flaws and loopholes in the existing proxy signature schemes, we propose three improved schemes, which have higher security and overcome the existing shortcomings in the original schemes. In addition, we propose a anonymous proxy signature based on the elliptic curve crypotosystem, which has the characters of high security and less length of key. Compared with the schemes based on the discrete logarithm problem, the scheme has higher security.The anonymous proxy signature scheme with a credible third party and the anonymous proxy signature scheme without a credible third party are both the anonymous proxy signature schemes based on the protection of proxy signer’s privacy and both have certain shortcomings and loopholes, such as original signer’s forgery attacks and original signer’s public key substitution attacks and so on. Against the defects of the anonymous proxy signature scheme without a credible third party, we present an improved scheme with higher security, which eliminates the above attacks and satisfies the safety requirements of the anonymous proxy signature based on the protection of proxy signer’s privacy. The anonymous proxy signature scheme based on the confidentiality of content possesses the defects of designated recipient’s forgery attacks and abuse of authority by the proxy signer. The two improved anonymous proxy schemes can overcome the above flaws and satisfy the safety requirements of the anonymous proxy signature based on the confidentiality of content.更多还原