Image encryption approach using ikeda map and vertical and horizontal blocks

In some works Arnold cat map [4] is used as the chaotic function to permute the pixel and cause disturbance in it. These operations are done on the semi-encrypted image and then horizontal blocks are combined to give the final encrypted image. It should be noted that the actual contents of x are not modified in this operation. Now, Img3 is taken for applying row wise operations. A flat histogram indicates that pixel intensities at all pixels in image are same in frequency. On the other hand, a meaningful image would have an uneven histogram indicating some information present inside it. For obtaining correlation coefficient values, randomly a pair of 3000 pixels were chosen from both plain and encrypted images in all the three directions-horizontal, vertical and top-right diagonal. Using simple bit XOR operations and blocks of image in horizontal and vertical directions, encrypted image is obtained. The encrypted image is tested for statistical properties, key analysis and information entropy values. Hence there is a requirement of developing an encryption algorithm which can convert the image data into some unrecognizable form (called encrypted form). Chaotic system in image encryption was first used by Matthews [2].