Algorithm Analysis And Collision Research On Hash Function

With the popularization and spread of Internet, the problem of network security becomes more and more serious, such as sending message, modifying message's contents and order for some reason. To sign a message using public-key algorithm is poorly efficiency, so we often combine digital signature with one-way hash function to improve efficiency. Furthermore that two different messages have a same hash value is scarcely possible. We consider it is security digital signing a message using hash function.Designing or using hash function and Cryptosystem compress any arbitrary message into a specified target output message. One-way hash function has two important characteristics, such as Preimage Resistance and Second Preimage Resistance; Iit's to say "Resistance Collision". If two different messages have the same hash value, we say that "MD4 collision". This output message is message digest or hash value. At first, we describe the well-known message digest algorithm. As MD4 serves as the basis for most of the dedicated hash functions, then we focus on MD4 hash function, analyze the security of MD4 and give some properties of three nonlinear functions of the MD4 message digest algorithm. Using these properties, we discuss many collisions for every round function and their probabilities. Subsequently we improve an efficient attack on MD4 and implement the improving algorithm. Finally we can increase the collisions probability, decrease the complexity and we can find another message that produces the same hash value. We introduce a set of analytical techniques, single - step modification and multi - step modification during collision attack research. At last, subsequent tasks are considered in the future.