Improvement And Performance Analysis Of A Chaotic Hash Algorithms

Hash function plays an increasingly important role in data integrate, informationverification, and digital signature. With the announcement that MD5algorithm has beenbroken, the classic one-way Hash function exposes defects, therefore, how to constructmore secure and efficient Hash algorithm has become one of the research hotspots,recently.In2003, K.W. Wong will be the first encryption and Hash function throughthechaos together. This caused widespread concern in the study of Hashfunction. Inrecent years, Hash function construction based on chaos has become a researchhotspot in cryptography. The main research work of this thesis are as follows:(1) The basis of chaos theory is introduced explicitly. First, we simply introduce theissue of information security on cryptography. Then, we illustrate the development ofrecent Hash function. Finally, we describe the definition and characteristics of chaos.(2)Hash theory basis is introduced in detail from different aspects. To start with, weintroduce the definition and characteristics of Hash function, as well as the wideapplications of Hash function in aspects of information protection and verification. Then,we present the classification of Hash functions: keyed hash function and unkeyed hashfunction. Finally, we illustrate the frequently used construction methods, andperformance measurement methods of Hash function.(3) We analyze a chaotic hash function based on chaotic tent map with changeableparameter, and find out that the algorithm cannot resist forgery attack and resistcollision. Because of this, we use methods of message expansion and hash valueaggregation to improve the resistance of forgery attack and collisions. Theoreticalanalysis and computer simulation indicate that the improved algorithm has bettercharacteristics of one way, confusion and diffusion, and collision resistance. Wecompare the performance of the classic MD5algorithm, a novel Hash algorithm basedon double chaotic maps by Kang Xiaopei, and a lookup table based hash function byDeng Shaojiang with the improved algorithm, and the results show that the improvedhash algorithm has better performance in aspects of confusion and diffusion, andcollision resistance.At last, the research tasks of the dissertation are summarized, and some difficultproblems and further work are indicated.