Consensus On The Residue Class Ring (?) / N (?) Full Replacement Of The Existence Of The Md5 Collision Attack Methods

Permutation is a kind of special cryptographic function, which is widely used in cryptographic algorithm. Constructing a permutation that has a good cryptographical property is one of the important requirements in designing a good cryptographic algorithm.MD5 is one of the two international hash functions, which is widely deployed in digital signatures, data integrity, group signature, e-cash and many other cryptographic protocols. So its security is vital to these applications.There are two chapters in this paper. In the first chapter, we further give the definition of l -omni-direction permutation on the residue-class ring Z/nZ based on the study of omni direction permutation and discuss the l-omni-direction permutation's functional properties. Furthermore, the definition of the uniform omni-direction permutation is presented and a question about its existence is raised.In the second chapter, the conception, properties and main attacks of hash function are introduced, and the MD5 algorithm is also introduced. Then we present the modular differential attack on MD5 in detail, and preliminarily analyze the theoretical reason why this method can attack successfully.