Projection based permutation of color images

The encryption of images is based on two main complementary techniques: permutation and substitution of pixels. The strength of any encryption algorithm depends on the strength of both techniques. This paper presents an algorithm for rows and columns permutation of pixels. It introduces a virtual cylinder surrounding the image through which a virtual viewer looks at the image when rotating around it. The key idea is based on the fact that the line of sight of each pixel to the viewer intersects the cylinder surface at a given point. This point should be the same whatever the position of the viewer is. Therefore, it is used to find out the new pixel´s position corresponding to the original image in a new generated image which is viewed from another position. The new created image has then some pixels which stack up and others which become out. They are then reintroduced in the created holes in the new image. This reinsertion of pixels creates the expected permutation. Based on only two main parts of the key which can be reinforced by others and a substitution technique, the algorithm shows a strength transformation of images for the purpose of their encryption.