Analysis And Design Of Chaotic Stream Cipher

With the rapid development and extensive applications of computer and communication technologies, our society goes into information time. The establishment of information system has gradually become an essential foundation for nearly all fields of our society. As there exists confidential information in any organization, the security problem about this information has become the common focus of both academia and enterprises.Cryptograph provides the most basic method to solve the information security problem. There is natural relationship between chaos and cryptography: strong dynamical properties of chaotic system imply strong cryptographical properties, and the basic approach to design strong cryptosystem implies quasi-chaos. The boom of research on chaotic ciphers occurred from 1989, two chaotic ciphers schemes proposed by Matthews, Pecora and Carroll, and much more contributions are made to get many promising achievements. Although a number of recently proposed chaotic ciphers have been cryptanalyzed, many others have not been effectively attacked yet.This dissertation focuses on the analysis and design of chaotic stream algorithm. The main achievements and originality contained in this dissertation are as follows: Chaos theory is introduced in detail from different aspects and views, the definition of chaos is presented, the characteristics of chaotic dynamics are described, and the criterion and rule of chaos are given.The research status and advances of chaotic ciphers have been summarized, analyzed and overviewed. The analysis and design method of chaotic stream cipher have been expatiated in detail.A chaotic stream cipher by using external 128-bit key and multiple chaotic maps has been discussed. A fundamental defect of this cryptosystem is pointed out and a known plaintext attack is presented. Furthermore, a remedial modification is suggested, which avoids the flaw while keeping all the merits of the original cryptosystem.Based on Baptista's chaotic cryptosystem, we propose a secure and robust chaotic cryptographic scheme after investigating the problems found in this cryptosystem as well as its variants. A subkey array generated from the key and the plaintext is adopted to enhance the security. Some methods are introduced to increase the efficiency.