Abstract: The recent years have witnessed rapid developments in the field of image encryption algorithms for secure color image processing. Image encryption algorithms have been classified in different ways in the past. This paper reviews the different image encryption algorithms developed during the period 2007-2015, highlighting their contrasting features. At the same time a broad classification of the said algorithms into: (1) full encryption algorithm and (2) partial encryption algorithm, each further sub-classified with respect to their domain orientations (spatial, frequency and hybrid domains) have been attempted. Efforts have also been made to cover different algorithms useful for color images of various color spaces like Red-Green-Blue (RGB), Hue-Saturation-Intensity (HSI), Cyan-Magenta-Yellow (CMY) etc. Chaotic cryptosystems, various transforms like wavelets, affine transforms etc. and visual cryptography systems are being discussed in detail.
Keywords: RGB; HIS; CMY; Chaotic cryptosystem; wavelets; affine transforms and visual cryptography