The Research Of Chaotic Stream Cipher Algorithm Based On Polymorphic

Pseudo-random sequence plays important role in cryptography. Key management, communication system, digital signature and identity authentication can not get away from high quality pseudo-random sequence. Therefore, it is great significance to generate enough quantity pseudo-random sequence which meet the requirement of cryptography. Under the continuous progress of cryptanalysis and attack means, the method of generating traditional key stream (pseudo-random sequence) has been challenged. Recently, based on chaos pseudo-random sequence generator become one of the frontier topics of information security field.The present thesis relates to working contents as follows:(1) This thesis makes a detailed discussion on the basic knowledge about chaos theory and stream ciphers. Firstly, the statistical properties of m sequence which is generated from linear feedback shift register are given.Secondly, the definition of chaos and motion feature are given, the typical chaotic models are listed here, and advantage and disadvantage of chaos system is used to construct pseudo-random sequence generator. And then, to show the practical application of pseudo-random sequence generator that based on chaos theory by combining several pseudo-random sequence generator.(2) Making concrete exposition on the basic knowledge of polymorphism in cryptography. This thesis introduces the theory, basic principle and developing stage on polymorphism in cryptography, and then the difference between the thought of polymorphism cryptography and traditional cryptography was analyzed.(3) Direct against chaos pseudo-random sequence generator’s deficiency, which is analyzed and improved, and then puts forward a new method of constructing about pseudo-random sequence generator. The method according to chaos theory and the thought of polymorphism cryptography make that chaos mapping algorithm randomly arranged in self-compiling system, so that it can effectively against differential attack. Generated sequence by pseudo-random sequence generator has been done theoretical analysis and experimental simulation. The result shows random sequence which output by sequencer are good.(4) According to some question about chaotic stream cipher, literature cited constructive NDF safety chaotic model, this thesis puts forward based on Self-encoded NDF Stream Cryptosystem. Firstly, Kelber condition and entropy criterion can be satisfied simultaneously by the method constructive NDF safety chaotic sub-model. And then according to switching principle, we random selecte NDF chaotic subsystem to complete plaintext’s encryption. Decryption process is inverse operation of encryption. By theoretical analysis and experiment simulation, ciphertext’s random which is generated by the algorithm is good, and example encryption applied effect is good.