【作者】 杨威；

【导师】 吴国凤；

【作者基本信息】 合肥工业大学 ， 计算机软件与理论， 2007， 硕士

【摘要】 Internet的迅猛发展，信息共享程度的日益增高，导致信息安全问题日渐突出。有人提出的解决办法是降低信息共享程度，这显然是不可取的。唯一的方法就是通过数据加密。本文以数据加密的起源密码学作为切入点，介绍了如今几种主流的数据加密方案。首先，借助一个具体实例，分析了数据加密标准DES加密的全过程，并指出目前DES存在的应用误区。而后，介绍了公开密钥RSA算法，并用数论知识证明了解密原理。此外，给出计算机处理“大整数”的一种解决方法。鉴于用户口令通常用MD5加密保存，通过暴力破解MD5实验，本文指出了24位以上的口令是非常安全的。对于大数据对象，比如视频、图像、声音、海量数据库文件的保密存储，需要高速，安全稳定的加密方案，作者推荐可变长密钥加密算法Blowfish。对于而今最为前沿的椭圆曲线加密和混沌加密，本文用了大量的篇幅进行探讨，椭圆曲线加密的所有细节都被剖析。文章指出：椭圆曲线具有最高的“实际安全度”。混沌加密具有最高的“理论安全度”，但“实际安全度”却一般。而目前在外交，国防，军事领域广泛采用的伪随机序列加密标准，本文也进行了系统的论述，并编写程序对VB随机数发生器的均匀性和独立性进行了检验，发现均匀性符合统计要求，而独立性差强人意。更多还原

【Abstract】 The developingd internet and increasing information sharing brings about a serious Problem of information security.Some people suggest reducing the degree of informationsharing, obviously, this is undesirable, data encryption is the only choice.The dissertation regards the origin of data encryption as cut-into-point,introducing several popular data encryption standards of time.First, Through an example, the dissertation analyzes simply the full progress of DES , and points out some mistakes of application.Then, introducing RSA ,and proveing the theory of data encryption by number theory, besides the dissertation presents a standalone point of computer processing big numbers.Because of user passwords usually are stored with MD5 ,through a violence cracker MD5 test,the dissertation consider up 24 bytes passwords as very secure.With respect to big data objects memory, such as video, picture, audio and massive database files, variable length data encryption standard Blowfish is a solution.The most advanced ECC and chaotic encryption ,the dissertation uses quantities of contents to research. All ECC’s particular is analyzed.The dissertation thinks ECC is the most secure on the "practical security degree ", while Chaotic Encryption is the most secure on the "theoretical security degree",but weak on the practice.Then the dissertation introduces the pseudo-random number stream cipher which is widely used in diplomacy, national defense and military,By testing the VB pseudo-random number generation’s uniformity and independence .Drawing a conclusion of uniformity is good while independence is weak.更多还原