Cryptanalysis Of Hash Functions And Improved Design Of Wide Pipe Hash Structure

This thesis deals with the analysis and design of cryptographic Hash functions arefundamental components of many cryptographic applications such as digital signatures,authentication, key derivation, random number generation and many others. Due to thisversatility they are considered as the “Swiss army knives” of modern cryptology.A Hash function is a one-way mathematical function that takes a message ofarbitrary length as input and produces an output of fixed (smaller) length. In recentyears, several of the approved cryptographic Hash functions which are generallyinspired by MD4have been successfully attacked, and serious attacks have beenpublished against the world-wide standard SHA-1. In response, the National Instituteof Standards and Technology (NIST) has opened a public competition to develop anew cryptographic Hash algorithm, SHA-3, to replace the older SHA-1and SHA-2Hash functions.The first part of this thesis is focused on the analysis of the Hash functionKECCAK, the finalist of this competition. We find a method for getting the differentialand linear distinguisher by analyzing its differential and linear property. Then, wedemonstrate a distinguisher of4rounds on KECCAK using its rotation and z-periodicproperty. Finally, we introduce the concept of zero-sum, and obtain a distinguisher of17round KECCAK.The second part of this thesis is focused on the design of Hash functions. Wepropose a new structure based on the wide pipe Hash model called SWP. Then, weanalyze its properties of collision resistance by investigating the complexity. Andfinally, we demonstrate a compare with the ordinary Hash structure and some newHash model.