Histogram analysis The information given by an image histogram represents the statistical distribution of pixels values. Enciphered images must be similar to random ones and lead to a pseudo-uniform distribution (uniform histogram), unlike plain images that have irregular distributions depending on the image content. We can see from Fig. 7 that histogram of the three ciphered images is uniform with respect to the three RGB color: red, green and blue channels. Consequently, no statistical attack can reveal any information about the plain image without knowledge of the secret key. Note that the Text image (c) contains only black and white pixels and by the way the corresponding histogram represents only the number of black and white pixels, while the corresponding ciphered image is a gray-scale random one according to its histogram.