计算机应用 ›› 2010, Vol. 30 ›› Issue (05): 1206-1208.

• 信息安全 • 上一篇    下一篇

一种使MD5算法产生更强雪崩效应的方法

张鑫彦1,闫德勤2   

  1. 1. 辽宁师范大学计算机与信息技术学院
    2. 辽宁师范大学
  • 收稿日期:2009-11-26 修回日期:2010-01-15 发布日期:2010-05-04 出版日期:2010-05-01
  • 通讯作者: 张鑫彦
  • 基金资助:
    国家自然科学基金资助项目;中国科学院自动化研究所复杂系统与智能科学重点实验室开放课题基金资助项目;辽宁省教育厅高等学校科学研究基金资助项目;大连市科技局科技计划项目

Generating stronger avalanche effect in MD5 algorithm

  • Received:2009-11-26 Revised:2010-01-15 Online:2010-05-04 Published:2010-05-01

摘要: 通过研究不同的差分分析对MD5算法的攻击后发现,差分分析攻击之所以可以成功,是因为在MD5算法中改变了明文中一些特定位,而这些特定位的改变在许多轮中最多只影响链接变量的几个位,并且这些小的差分能在随后的多轮操作中得到纠正,从而产生了碰撞。这就说明原MD5算法的雪崩效应不能阻止差分分析的攻击,而为了提高MD5算法的安全性,必须提高其雪崩效应的敏感性。分析结果表明,用动态明文变化函数对MD5算法进行修改,能使其产生更敏感的雪崩效应,以此来有效防止差分分析攻击,提高MD5算法的安全性。

关键词: Hash函数, MD5算法, 差分分析, 链接变量

Abstract: By studying the differential analysis attacks on MD5 algorithm, it was found that why the differential analysis attacks could be successful was due to the change of individual bits of message. The alteration only influenced a small part of chaining variable, and these few differences could be rectified after continuative loops. Then, the collision was generated, and the avalanche effect of the original MD5 algorithm could not prevent differential analysis attack. To enhance the security of MD5 algorithm, the sensitivity of the avalanche of the MD5 algorithm should be increased. The analytical results indicate that the modified MD5 with Variable Plaintext Function (VPF) can be more sensitive to the avalanche effect, so as to effectively prevent the differential analysis attack and increase the security of MD5.

Key words: Hash function, MD5 algorithm, differential analysis, chaining variable