电子现金支付协议的设计

【作者】 孟纯煜；

【导师】 殷新春；

【作者基本信息】 扬州大学 ， 计算机应用技术， 2007， 硕士

【摘要】 电子商务是信息化社会的商务模式,是商务的未来,它不仅使传统商业变得更加快速、便捷,还将从根本上改变传统商业结构和运作模式。现在阻碍电子商务发展的一个重要因素就是安全问题,特别是电子支付的安全问题,使得许多客户在网上浏览,采用传统的方式在网下购物。为了让更多的人能接受电子商务提供的服务,保证电子交易的顺利进行,我们必须提供安全、保密、高效的电子支付系统!当今电子支付系统大致可以分为三大类:基于信用卡类支付系统、基于电子支票(Electronic Check)类支付系统和基于电子现金(Electronic Cash)类支付系统。自1983年D.Chaum发表第一篇关于电子现金系统的论文以来,电子现金成了密码学的研究热点。这么多年来对电子现金支付的研究也取得了不少进展,但这些方案在安全性、效率和实用性上存在顾此失彼,仍有许多问题有待进一步研究。本论文旨在分析前人协议的基础上,结合新的密码学知识,设计出安全、高效且实用的电子现金支付协议。取得的主要成果如下:1.设计了一个入侵弹性的电子货币系统。因为现有的电子货币系统大多使用普通的签名算法,这使得一旦发币行的密钥被破坏,则所有以前发行的货币均失效。为了使密钥泄漏带来的危害达到最小,我们设计了一种采用入侵弹性签名算法的电子货币系统。入侵弹性是目前最强有力的密钥进化模型,该模型不但在每个时间段开端固定的更新密钥,而且在每个时间段内可多次随机地刷新密钥。分析表明,该方案在当前或已过期时间段的密钥被破坏的情况下仍然前向安全,同时,由于货币有生存期,从而减小了存储量与查询代价。2.设计了一个基于双线性对和部分盲签名的电子现金支付方案。我们利用双线性对在密码学中的应用,并将部分盲签名加入其中,其在完全盲签名的基础上加入了签名方的身份标识信息,既有效保护了消息发送方的隐私权,又使得存款时,只需要访问该签名方(即银行)的数据,从而提高了处理效率。分析表明,该方案安全性能强、效率高。3.设计了一个基于可链接环签名的电子现金支付方案。一般的电子现金支付是事后检测有无重复花费,这样重复花费已成事实,再去追踪,损失大,纠纷多。我们在可链接环签名协议的基础上设计了一种新的电子现金支付方案,将可在商家消费电子现金的消费者组成一个用户团,便于管理和实现环签名,同时实现了事前检测有无试图重复花费,从而避免了重复花费造成的损失和纠纷。分析表明,该方案是一个安全实用的电子现金支付方案。4.设计了两个基于身份有可信中心的电子现金支付方案。基于身份的密码系统其公钥可根据签名方的身份计算得出。方案设立了一个中央银行,其担当生成私钥的可信任机构,需发行电子现金的银行要向中央银行提出申请,公钥由发币行的身份计算得出,这样使得发币行的责任明确,不可推诿,私钥由中央银行统一生成。分析表明,这两种方案安全性能强、效率高。5.设计了一个基于身份无可信中心的电子现金支付方案。现有的基于身份的电子现金支付方案都需要可信任的私钥生成中心(PKG),因为由PKG统一生成私钥,所以存在伪造合法电子现金的可能,为此我们设计了一个基于身份无可信中心的电子现金支付方案,签发电子现金的私钥由PKG和发币行共同产生。分析表明,该方案更加安全实用。6.设计了一个基于盲聚合签名的电子现金支付方案。在一个电子现金支付系统中,假设用户在n个不同的银行都有账户,当他在任意n-1个银行账户内的余额累加起来都不足够一次支付时,他需要在这n个银行都取款,然后才有足够的电子现金支付给商家,随后商家要将这n笔电子现金拿到各个银行进行验证,无误后再将钱划到自己的账户上,这需要浪费很多的时间和存储空间,针对这种情况,我们将盲聚合签名方案应用到电子现金中,用户可将n个有效的电子现金进行聚合,形成一个聚合电子现金,将它支付给商家,这样商家可以只拿这个电子现金到一个银行进行验证即可。分析表明,该方案大大减少了存储空间,也降低了数据传输过程中的带宽要求,同时将n次验证减少到1次验证,节省了大量的时间,提高了验证效率。更多还原

【Abstract】 Electronic commerce is the business mode of the information society and it is the future of the business. It not only makes the traditional commerce more fleet and convenient, but also changes the traditional commerce structure and running pattern radically. The security of e-commerce is one of the most important obstacles to hold back its development, especially the security of the electronic payment. Many customers browse on the network while buy off line by the traditional way. In order to make more people accept the service provided by the e-commerce and ensure the electronic trade to go along smoothly, We must provide more safe, security and efficient electronic payment system!At present, the e-payment system could be classified approximately as three categories: credit card、electronic check and electronic cash. E-cash becomes the hotspot in security field since upon which D.Chaum published the first paper in 1983. We have many progress on the research of e-cash for a long time. However, these schemes could not satisfy security, efficiency and practicability simultaneously, thus a lot of problems should be further investigated. The purpose of this paper is to analyze former electronic cash protocols and design secure, efficient and practicable electronic cash systems with new progress of cryptograph. The main achievements of this paper are as follows:1. We designed an intrusion-resilient e-cash system. Because existing e-cash system mostly used ordinary signature arithmetic, the former issued e-cashes would be invalidate wholly in case the private key of the issued e-cash bank had been destroyed. In order to reduce the harm of the private-key’s leakage in greatest degree, we designed an e-cash system that using intrusion-resilient signature algorithm. At present, Intrusion-resilient key evolving model is the most powerful model which not only evolved the private key fixedly at every period threshold but also evolved the private key of the issuer more randomly in every period. The analysis showed that our scheme was also forward-secure at the instance that the present private key or the past private key was destroyed, meanwhile, each coin was endowed with a life circle, which reduced storage and the checking cost.2. We proposed an E-cash scheme from bilinear pairings and partially blind signature. The protocol is based on bilinear pairing and partially blind signature, it can protect the message sender’s privacy efficiently, at the same time, promote the depositing efficiency by embedding the signer’s information. The analysis indicated that our scheme had secure point and high efficiency.3. An electronic cash scheme based on linkable ring signature has been proposed. Most E-cash payment systems checked the double-spending after they were fact, thus to trace it makes more loss and entanglement. Based on linkable ring signature, an e-cash scheme is put forward. Consumers that want to consume E-cashes must register in the merchants in advance. So it’s easy to manage and realize the ring signature,at the same time,we realized the checking of double-spending beforehand and avoided the loss and entanglement. The analysis proved that our scheme was secure and applied.4. We designed two identity-based E-cash schemes. The public key of the identity-based cryptography is computed by the signatory’s identity. At the same time, a center bank which acted as a trusty third party is set up in our scheme. The private key is generated by the center bank. The bank which wants to issue the E-cash would lodge an application to the center bank. The bank’s public key is computed by its identity and its responsibility is clear .The private key is generated by the center bank. The analysis showed that the two schemes had secure point and high efficiency.5. We designed an identity-based E-cash scheme Without a trusted party. The current identity-based E-cash scheme need to trust a private key generator(PKG). Because the private key is generated by the PKG, to forge a legal E-cash is possible. We designed an identity-based E-cash scheme without a trusted party. The private key that the bank signs an E-cash is generated by the PKG and the bank together. The analysis showed that this scheme was more secure and practical.6. We designed an electronic cash scheme based on blind aggregate signature. In an e-cash system, one has to withdraw deposit from n banks when his any n-1 accounts (in different banks) could not disburse his transaction. Later, the merchant verified the n E-cashes in every bank. Without mistakes, the merchant has the E-cash. This method would waste much time and storage space. Then this paper applied blind aggregate signature in these n e-cashes which turned it into an aggregated one and pay it to a merchant. So the merchant may verify the aggregated one in some bank. The analysis showed that this scheme reduced storage space greatly and reduced the bandwidth in the process of data transfer, at the same time, cut down the verification from n times to one time, saved plenty of time and improved efficiency.更多还原