Contents I. Introduction
In the digital era, family pictures, scientific graphs, medical images, and other important images are stored in computers and transmitted through the internet to share with people. The images contain essential personal, technical, or medical information. Hence to protect such kinds of image data from unauthorized users there is a demand for suitable image cryptosystems. Since images have highly correlated adjacent pixels, and higher data redundancy than the text data, the conventional symmetric-key encryption algorithms, for example AES, and IDEA used for text data are not suitable to reduce the correlation between the adjacent pixels of the images and secure it. Therefore different techniques are integrated with the image encryption algorithms such as chaotic maps [1], DNA coding [2] and wavelet transmission [3] to design the robust image cryptosystems. In image cryptosystems, a confusion-diffusion architecture based mechanism, as shown in the figure 1a is considered. Here, the image content is shuffled with iteration. Subsequently, a suitable substitution mechanism is deployed. Overall, such a process is continued several times untill the visual and statistical information gets hidden, and it reaches the desired security level. In the confusion-diffusion mechanism, different chaotic maps are used.
