Research On Application Of Computer Encryption And Decryption Based On Chaos Theory

Due to the inherent uncertainty in the nonlinear dynamic systems,chaotic sequence is deterministic, not periodic, with good randomness and bounded convergence, and is sensitive to initial value,making it has good cryptographic properties. Chaos, the theory of relativity and quantum mechanics, are regarded as the three great physics revolution. As one of the most important scientific discoveries in the20th century, chaos has been adapted to astronomy, meteorology, ecology, economics, and many other fields. With the rapid development of multimedia technology and network communication technology, in the face of all kinds of security transmission of data in the Internet, the application of chaos theory in the field of secure communications has become an important frontier research of modern cryptography.Thanks to the extensive theoretical research at chaos, at present partial properties of chaotic systems have been known.These chaotic systems such as the logistic map and Lorenz map, henon mapping, chebyshev map, farmers mapping, Tent mapping, etc., are more than enough for us to use. Their formulas are simple, so that we could get a high computational efficiency and their chaotic sequences are certain4nd renewable. This article selects advanced logistics and chebyshev sequences as chaos examples to explore their practical application in secure communication. Firstly, the author analyzes the properties such as aperiodicity, unpredictability, pseudo randomness, self/mutual correlation, etc., of the above two kinds of chaotic sequence, and the author also implements simulations for chaos with the use of computer. Only with the good properties, the chaotic sequences generating from chaotic mappings can be used to encryption.After that, this paper analyzes the text data, audio data, the characteristics of image data, and designs the chaotic mask algorithm considering with their respective characteristics.Then through the MATLAB2010software, this paper implements the encryption and decryption simulation of the text, audio, and image signal respectively under the condition of both improved logistics mapping and chebyshev mapping. These two kinds of mapping have large key space making the safety performance of the algorithm good. Finally, this paper proposed a composite of two kinds of chaotic sequence encryption algorithm to get a higher security of the algorithm. The simulation results of chaotic encryptions and decryptions show that as the modulation disrupts the original chaotic sequence, and the chaotic sequence has been difficult to analyze, analyzing the disrupted sequence is even more difficult. The algorithm can resist linear statistical analysis, reconstitution attack, differential attack, brute force attack, and the possibility for the attacker to reconstruct message from disrupted signal is almost to zero. If someone want to decode to get the message, he must know the chaotic model, decryption algorithm and the key, otherwise there is no way to decrypt the original data.