A Nonlinear Cryptosystem Based on Structure Phase Masks, QZ Modulation, Using Gyrator Transform Domain

This communication delves into an encryption methodology centered around the gyrator transform and the utilization of diverse structured phase masks (SPMs). Unlike conventional random phase masks (RPMs), this approach substitutes them with structured phase masks (SPMs) derived from Devil's Vortex Fresnel Lens (DVFL) and Fresnel Toroidal Lens (FTL). The primary objective behind incorporating these phase keys is to bolster algorithmic security by expanding the key-space. Structured phase masks (SPMs) boast the capability of housing multiple storing keys within a single-phase mask, owing to their nature as diffractive optical elements (DOEs), making them arduous to replace. Consequently, they introduce additional security parameters that enhance the system's robustness and reliability. The efficacy of the proposed schemes has been validated through computer simulations, with assessments conducted via the computation of mean-squarederror (MSE) and peak signal-to-noise ratio (PSNR) between the original and decrypted images. Furthermore, these schemes have undergone scrutiny regarding their sensitivity to various encryption parameters and their resilience against noise attacks.