Security Analysis Of Application Modes And Components Of Hash Functions

Hash functions are the fundamental components in modern cryptography and also key modules in communication protocol and information security systems. Hash functions are widely used to achieve certain security goals such as data integrity, message authentication, digital signature, key exchange scheme, etc. Hence security analysis of Hash functions is very important both in theory and in practice.This thesis firstly introduces the basic theory of Hash functions, and then studies the properties of a new class of functions as Hash function components. Furthermore, when the security of the iterated structure of Hash function is analyzed in detail, we emphasize on studying an important application of Hash functions - constructing message authentication codes (MAC) schemes, and analyzing its security.This thesis includes the following two aspects of Hash functions:(1) Mixed-operations and T-functions are used for design of Hash functions. We study the properties of a new class of functions based on mixed-operations and obtain a necessary condition when is invertible. Also we consider the case when ( )f ( x ) = x + ( x <<< a )∨C mod 2nf x degenerates into a T-function.(2) The constructions and performances of some MACs are introduced. We analyze the security of a class of message authentication codes based on Hash functions. This MAC is so insecure that the attacker can easily forge messages without analyzing the security of Hash functions.