Digital Image Encryption Based On Chaos Theory

With the rapid development of Internet and multimedia communication technology, the security of digital image information has become a new research hotspot. Digital image has its intrinsic characteristics, such as dramatic and visual, so it has been widely applied in many areas, such as network communication, medical, military, etc. These applications bring much convenience for people's daily life, and at the same time people are increasingly concerned about the security issues. Therefore, how to ensure the security of the digital image in practical applications has become a hot topic in information security field.In reality, as the limit of image's own characteristics, traditional cryptographic algorithms cannot effectively guarantee an ideal image encryption effect. From the end of the 20th century, in order to obtain a better encryption property, researchers began to study the image encryption technology by applying chaos theory and proposed some related algorithms. These schemes not only greatly enrich the theoretical system of image information security, but also point out new directions for future research. Based on the fundamental knowledge of chaos theory and wavelet transformation, two kinds of hybrid image encryption algorithms are proposed in this paper. The main work is as follows:1. This paper presents the background and significance of image encryption technology research, briefly expounds the basic theory of image encryption and summarizes the research status of chaotic image encryption algorithms. Then, the relevant knowledge of chaos theory and its relationship with cryptography are presented. Meanwhile, it outlines several design guidelines for chaotic image encryption system. Finally, some common chaotic system models are described.2. This paper emphasis on two kinds of common two-dimensional chaotic systems. And according to them, a novel hybrid image encryption scheme is proposed. This scheme firstly scrambles the original image by point-by-point with the chaotic sequences obtained from 2D Logistic Map and then diffuses the scrambled image with using couple diffusion matrices generated by 2D Henon Map. The results of simulations show that this algorithm can conquer the shortcomings of low-dimensional and high-dimensional chaotic systems. It can not only improve the security, but also reduce the time overhead of image encryption. It is proved that our algorithm has a good image encryption performance.3. This paper introduces the basic theory of wavelet transformation. Based on the wavelet transformation, we propose a novel mixed-domain image encryption method by using chaotic systems and DWT. In this algorithm, four frequency domain components are generated by discrete wavelet decomposing. Then the low-frequency component is scrambled and diffused with the chaotic sequence generated by 2D Logistic Map, respectively. In order to improve the encryption property of our algorithm, we globally diffuses the middle encrypted image from the wavelet reconstruction using the chaotic disorder sequence obtained by ID Logistic Map. Finally,it achieves the encrypted image. The results of experimental simulation demonstrate that our proposed mixed-domain encryption algorithm is of good image encryption performance.