Color information security system using discrete cosine transform in gyrator transform domain radial-Hilbert phase encoding

A novel color-information encryption technique based on discrete cosine transform and radial Hilbert phase mask in gyrator transform domain is proposed. In this work, the radial Hilbert phase function is employed as selected phase mask. Before the encryption, the original color image is converted into independent channels, i.e. red, green, and blue. Each channel is encrypted using first random phase mask and discrete cosine transform at input plane, and then the first gyrator transform is executed. The obtained image is again encrypted using second random phase mask and discrete cosine transform at frequency plane, and then transmitted through radial Hibert phase mask. The gyrator transform is performed on the transmitted image. The integral orders of radial Hibert phase mask and transformation angles of gyrator transform in each channel provide supplementary keys to enhance the security. The proposed system evades the misalignment problems. Numerical simulations are demonstrated to test the security, validity, and efficiency of the proposed algorithm.

► DCT and radial-Hilbert phase mask in gyrator transform domain is proposed for encrypting an image.
► The parameters of radial-Hilbert phase mask and gyrator transform in each channel are main keys.
► The optical implementation of the color-image encryption technique has been presented.
► The security system avoids problems arising from misalignment.
► Numerical simulations are performed to demonstrate the feasibility of the scheme.