Several Image Encryption Algorithms Based On Chaotic Systems

With the rapid developments in Internet and information technology, digital multimedia information such as audio and video can be disseminate over the Internet conveniently. Being a main form of expression for multimedia data, visual and vivid digital image is becoming a primary communication method today. However, there exists potential safety hazards of digital image while brings convenience to our life.Image encryption is one core technology in image security. There are many disadvantages in traditional encryptions, and a lot of encryptions for images are put forward. This paper studies on chaotic technology and its application in digital image encryption. Some contributions are as follows.(1) A new color image encryption based on high dimensional chaotic systems is proposed. The high dimensional chaotic systems have many advantages as more complex mechanism, increasing the key space, more ruleless for the time series of the system variable. Based on these reasons, a new encryption cryptosystem is proposed. Moreover, substitution-diffusion architecture is used to improve the security of the image encryption algorithm.(2) An image encryption scheme based on improved substitution-diffusion with variable control parameters is proposed. The author modified the substitution-diffusion architecture. The pixel value mixing effect is contributed not only by the diffusion function but also the modified substitution process. So the speed of confusion of pixels is faster. And in this algorithm the control parameters in each permutation are not fixed, but are determined by the plain-image which can improve the security of the algorithm.(3) A method for generating substitution boxes based on iterating the logistic map is presented and a block cipher using dynamic S-boxes is proposed. The plaintexts are divided into blocks and encrypted with different S-boxes. The cipher blocks are obtained by 8 rounds of substitution and the Modulo-Plus function. To improve the security of the cryptosystem, a cipher feedback is used to change the state value of the logistic map, which makes the S-boxes relate to the plaintext and enhances the confusion and diffusion properties of the cryptosystem.