MD5算法的分析与研究

发布时间：2019-05-08 18:11

【摘要】：Hash函数是密码学重要的组成部分,它广泛应用于电子商务、信息安全和电子政务等安全性要求比较高的领域中,同时也是实现数字签名、消息的完备性和消息可认证性的重要工具。MD5算法是MD结构的典型代表,也是Hash函数中的一员。因此,通过对MD5算法的研究与分析,可以更好的理解Hash函数的基本研究方法。王小云教授利用差分攻击的方法,成功找到了MD4、MD5、RIPEMD和HAVAL-128的碰撞消息。本文主要对MD5碰撞攻击用到比特追踪技术和消息修改技术进行研究,在此基础上,总结了碰撞攻击的一般步骤:引入明文消息差分、选择差分路径、确定差分条件。最后,对已有的碰撞攻击算法提出了一定的改进方案,在一定程度上可以降低碰撞攻击算法的计算复杂度。另外,本文还对MD5算法进行了一定的改进,主要是变更原始非线性函数、变更初始值、变更每一圈的常数、更改迭代流程。实验结果表明,改进后的碰撞攻击算法在一定程度上降低了计算复杂度。改进的MD5算法在抗碰撞攻击性、雪崩效应以及效率性等方面都有所提升。
[Abstract]:Hash function is an important part of cryptography, it is widely used in e-commerce, information security and e-government security and other areas of high security requirements, but also to achieve digital signature, The MD5 algorithm is a typical representative of the MD structure and is also a member of the Hash function. Therefore, through the research and analysis of MD5 algorithm, we can better understand the basic research method of Hash function. Professor Wang Xiaoyun successfully found the collision message between MD4,MD5,RIPEMD and HAVAL-128 by differential attack. In this paper, the bit tracking technique and message modification technique used in MD5 collision attack are studied. On the basis of this, the general steps of collision attack are summarized: introducing plaintext message difference, selecting differential path and determining the difference condition. Finally, an improved algorithm is proposed to reduce the computational complexity of the collision attack algorithm to a certain extent. In addition, the MD5 algorithm is improved mainly by changing the original nonlinear function, changing the initial value, changing the constant of each cycle and changing the iterative process. The experimental results show that the improved collision attack algorithm reduces the computational complexity to a certain extent. The improved MD5 algorithm has been improved in anti-collision attack, avalanche effect and efficiency.
【学位授予单位】：杭州电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN918.1

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