Color image encryption using affine transform in fractional Hartley domain

A novel scheme for color image encryption using the fractional Hartley and affine transforms is proposed. An input color image is first decomposed in its RGB (red, green and blue) components. Each component is bonded with a random phase mask and then subjected to a fractional Hartley transform followed by affine transform. Thereafter, a second random phase mask is applied to each component before the final transformation by fractional Hartley transform resulting in a component-wise encrypted image. Finally, all three components are combined to give a single channel encrypted image. The scheme is validated with numerical simulations performed on a color image of size 256 × 256 × 3 pixels using MATLAB 7.14. The use of affine transform along with fractional Hartley transform adds to the security. The scheme is evaluated for its sensitivity to the parameters of the fractional Hartley and affine transforms. On analysing the plots of correlation coefficient and mean-squared-error, the scheme is found to be highly sensitive to the encryption parameters. Also, it is evaluated for its robustness against the usual noise and occlusion attacks. The proposed scheme is secure and robust owing to multiplicity of encryption parameters introduced through the type of transforms used.