Asymmetric Optical Image Triple Masking Encryption Based on Gyrator and Fresnel Transforms to Remove Silhouette Problem

An asymmetric scheme based on equal modulus decomposition (EMD) and singular value decomposition (SVD) encrypted using Fresnel and gyrator transform is proposed to enhance the security of the system and to make it free from silhouette problem. In this technique, it uses triple masking technique where double masking is done through random phase mask (diffusers) and the third masking is done through EMD using \(\theta\). After the triple masking the distorted obtained image is decomposed into segments (U, S, V) using SVD and each decomposed encrypted segment is transmitted through different channels and kept at different locations. The extra degree of freedom (keys) provided by triple making technique increases the key space hereby enhances the optical encryption security that makes it difficult for an attacker to find the exact key to recover an original image. It also makes it highly resistant to many conventional and iterative attacks. The robustness of the asymmetric proposed cryptosystem has been examined by simulating on MATLAB 8.3.0 (R2014a). The experimental results are provided to highlight the effectiveness, robustness and suitability of the proposed cryptosystem and to prove the feasibility and validity of the proposal.