Nonlinear image encryption system using the Gyrator transform and truncation operations

Abstract

A new nonlinear system for image encryption using the Gyrator transform (GT) and the truncation operations is proposed in this work. The original image is encoded in phase at the beginning of the encryption process. The encryption-decryption system is based on the double random phase encoding (DRPE) in the Gyrator domain (GD). The rotation angle of the Gyrator transform is a new key that increases the security of the encryption system. The amplitude and phase truncation operations are nonlinear and no unitary, these truncation operations allow to select the information of amplitude or phase from a complex-valued image. We apply the truncation operations in the image encryption-decryption system in order to generate two new keys, convert the system in nonlinear and increase the security of the system. To retrieve the original image without error (noise-free) in the decryption system, it is needed all the correct security keys: the two RPMs, the rotation angle of the GT and the two key generated by the amplitude and phase truncation operations. The feasibility of this nonlinear encryption-decryption system is verified and analyzed by numerical simulations.