混沌加密機制在訊號傳輸應用之特性分析

Abstract

本篇論文主要在討論混沌理論用於加密機制的好處，分析原始基本架構中的週期特性，此外還針對原始系統中某些特定初始值的短週期現象（weak state）提出兩個改良的加解密架構，第一個改良架構稱為Double LCIRC Block，主要是針對系統中混沌的部分，提高其非線性，藉此提高系統的週期長度，從結果可以發現所有原始系統中具有短週期現象的初始值，在經過此架構後皆有提高其週期長度的現象，整體的週期表現則是呈現比較平均的現象；第二個改良架構稱為Double Encrypt Block，主要是以提高系統複雜度為目的，所以將加解密方塊各重複兩次，此架構同樣的也改善了短週期的現象，並且還大幅度的提高各種初始值組合的週期長度，使整體的的週期長度都分佈在長度較長的區域。

This thesis reveals the advantages of chaotic encryption scheme. The property of the period of the original system is also analyzed and discussed. Another purpose of this thesis is to introduce two modified systems which improve the weak state problem of the original system. For first system, the LCIRC block is doubled in order to increase nonlinearity of the chaotic part of the original system. The variation of this system is reduced. For second system, the encryption block is doubled for the purpose of higher complexity of the original system. The period of all possible initial state pairs is raised extremely. According to the results of these two systems, the weak state problem is really improved by these two modified systems.