Research On Color Image Encryption Algorithm Based On Spatiotemporal Chaos System

With the rapid development of computer technology and the widespread application of multimedia technology, more and more multimedia information is transmitted through the network. Digital image has become one of the most common and important information carriers due to its characteristics such as a large amount of information, visualization and perceptual intuition. How to store and transmit image information safely in a relatively open network has become an urgent and challenge problem. Because the chaotic signals have cryptographically desirable properties such as extreme sensitivity to initial condition and parameters, long periodicity, ergodicity, high randomness and mixing, the chaotic systems are very suitable for image encryption. In recent years, chaos-based image encryption has become an active research direction in the field of information security and has attracted increasing attention.Based on the spatiotemporal chaos, discrete wavelet transform and DNA sequences operations, this paper proposes two color image encryption algorithms, and analyzes the performance of the proposed algorithms. The main work and research results of this paper are listed as follows:1. A new lossless chaotic color image encryption algorithm is proposed based on YIQ color space and lifting discrete wavelet transform(DWT). Firstly, convert the original color image from RGB color space into YIQ color space. Decompose the color image in YIQ color space into its Y, I, Q components, and transform the components into the image sub-bands by two-level two-dimensional(2D) DWT, respectively. Then change the size of these sub-bands. Secondly, the 2D inverse DWT is used to reconstruct the intermediate encrypted image by the image sub-bands. Finally, the chaotic sequences are generated from the spatiotemporal chaotic system, and then are improved to get good stochastic properties. To further enhance the security of the encryption method, the improved sequences are employed to scramble the intermediate image. The scrambled image is transformed into RGB color space. Thus the resulting cipher-image is obtained. The experimental results show that the presented scheme is a lossless image algorithm with large key space and low pixel correlation, and suitable for digital image encryption.2. A digital image encryption algorithm is designed based on DNA sequences operations and spatiotemporal chaos. Firstly, the plain-image is converted into the DNA sequences matrices and perform DNA addition and subtraction operations on them. Then transform the DNA sequences matrices into the digital image and scramble the obtained image using the chaotic sequences generated by spatiotemporal chaotic system. Finally, diffuse the image by modifying the image pixel values. Experimental results and security analysis show that the proposed encryption scheme has a good encryption effect and high security.