Image encryption and the fractional Fourier transform

A number of method have been recently proposed in the literature for the encryption of 2-D information using optical systems based on the fractional Fourier fransform, FRT. In this paper a brief review of the methods proposed to date is presented. A measure of the strength/robustness of the level of encryption of the various techniques is proposed and a comparison is carried out between the methods. Optical implementations are discussed. Robustness of system with respect to misalignment and blind decryption are also discussed