Optical Cryptosystem of Color Images based on Fractional-, Wavelet Transform Domains using Random Phase Masks

摘要

Objectives: A technique based on optical color cryptosystem is carried out in the Fractional Wavelet Transform (FWT) plane. Purpose of this paper is to increase the key space there by the scheme become more secured. Methods/Statistical Analyis: The original images are segregated into three: R (red), G (green) and B (blue) color components. After that the each part is encoding independently using 4-f system of DRPE in FWT. The input images to be encrypted are multiplied by RPMs in spatial and frequency planes then subjected to FrFT and inverse FrFT, after that it subjected to Discrete Wavelet Transform. Coefficients from the Discrete Wavelet Transform are further multiplied each one by additional masks of different pixel from RPM. They are further inverse Discrete Wavelet Transform applied to get the encrypted images. Images are recovered by using the all correct parameters of FWT. Findings: Proposed algorithm is enough secured because combination of FrFT and DWT. The effectiveness of present technique is tested by computing MSE, Signal to Noise Ratio (SNR) between retrieved and input images. Role of encryption keys, occlusion and noise attacks have been verified in proposed scheme. Applications/Improvements: Security of any scheme is based on the keys used. Even a very strong or well-designed scheme can be attack easily if the keys are used in encryption is poorly selected. In this scheme keys are used in both the transforms so the key size is increased. Key space can be further modified for more security.