Color image cryptosystem based on discrete cosine transform in gyrator transform domain spiral-phase encoding

摘要

A new color image cryptosystem is proposed, which is based on discrete cosine transform and spiral phase encoding in gyrator transform domain. The random phase mask is replaced by a multiple-key spiral phase mask, because it is difficult to replicate and easy to align. In this scheme, a color image is decomposed into red, blue and green color channels. Each channel is encoded independently by using discrete cosine transform and then encrypted into a spiral phase mask. The resulting image is gyrator transformed. The operations are performed twice continuously to get multiplexed encrypted image at output plane. The rotation angles of gyrator transform along with the order, the wavelength, the focal length and the radius of a spiral phase mask of each channel provide multiple choice for the parameter of the proposed security system as encryption keys. The proposed optical setup avoids alignment problems. The performance, feasibility and effectiveness of the proposed algorithm are demonstrated by the numerical simulation results.