A protocol to cipher digital images based on cat maps and cellular automata

In this paper a novel symmetric protocol to cipher digital images is introduced. The protocol proposed in this work is based on the paradigm stated by J. Fridrich at 1998. Consequently, there are two iterative stages in the algorithm: The confusion stage permutes the pixels in the image using the Cat map, whereas in the diffusion stage, the pixel values (the color of each pixel) are modified sequentially such that a small change in the color of only one pixel is spread out to many pixels. This second phase is carryied out by means of a reversible cellular automaton. The proposed protocol is shown to be secure against the more important cryptanalytic attacks.