Analyse And Research On MD5 Algorithm

Hash functions play an important role in cryptography,widely applied in high-security areas,such as e-commerce,information security and e-government,besides,hash functions also are important tools for digital signature,data integrity and message authentication.MD5 algorithm,as a member of hash functions,is a typical representative of MD structure.Therefore,it is helpful to get the basis analysis method of hash functions to attack other hash functions through the research of MD5 algorithm.A series of hash functions such as MD4,MD5,RIPEMD and HAVAL-128 have been attacked by Wang et al.using differential analysis method.In this dissertation,we conducted a study of bit-tracking techonlogy and message modification technology,and summarized the main idea of collision attack of MD5: generating message differentials,control the differential paths,satisfaction the sufficient conditions.At last,this dissertation presented an improved collision attack algorithm on MD5,which can reduce the average computational complexity.In addition,this dissertation improved MD5 algorithm from the four aspects,transforming the original logical function,transforming register initial value,transforming each wheel constant and modification algorithm iterative process.The experimental results showed that improved collision attack algorithm on MD5 reduced the average computational complexity,the improved MD5 algorithm has been improved the collision-resistant,avalanche effect and efficiency.