Asymmetric Cryptosystem Using Structured Phase Masks in Discrete Cosine and Fractional Fourier Transforms

Abstract

For enhancement of the security, an asymmetric cryptosystem scheme is proposed for double image encryption based on a structured phase mask (SPM) in discrete cosine transform and fractional Fourier transform. The usage of SPM helps in increasing key spaces. Different keys are used at the time of encoding and decoding of an image in asymmetric cryptosystem which makes the system much more secure. The performance of the technique is carried out with the help of MATLAB R2018a (9.4.0.813654). This scheme is tested for two images and its validity is verified. The results are shown by the help of mean-squared-error (MSE), peak signal-to-noise ratio (PSNR) and relative error (RE). The reliability of the proposed system for noise attacks with references to sensitivity analysis is also confirmed. Evaluation of the statistical outcomes certifies that the suggested procedure is relevant and feasible. The procedure brings augmented security, and the experimental outcomes illustrate the supremacy of the recommended cryptosystem.