Unsymmetric Image Encryption Using Lower-Upper Decomposition and Structured Phase Mask in the Fractional Fourier Domain
Shivani Yadav, Hukum Singh · Recent Advances in Computer Science and Communications · 2020
Background: An asymmetric cryptosystem using Structured Phase Mask (SPM) and Random Phase Mask (RPM) in fractional Fourier transform (FrFT) using lower-Upper decomposition with partial pivoting is proposed to provide extra security to the system. The usage of structured phase mask offers additional parameter in encryption. In the encoded process the phase-truncation (PT) part is replaced by the LUDP that is by the decomposition part. Objective: Introducing an asymmetric cryptosystem with LUDP is to avert quick identification of encrypted image in the FrFT domain. Method: Input image is firstly convoluted with SPM, in FrFT and in LUDP then the obtained result is convoluted with RPM in inverse FrFT and in LUDP. Finally, the encoded image is attained. Results: The strength and legitimacy of the proposed scheme have been verified by using numerical analysis on MATLAB R2018a (9.4.0.813654). For checking the viability of the proposed scheme mathematical simulations have been carried out which determines the performance and better quality of an image based on key sensitivity, occlusion attack, noise attacks and histograms. Conclusion: A novel asymmetric cryptosystem is proposed using two phase masks one is SPM and another is RPM. LUDP is proposed in which the encoded procedure is different from the decoded procedure. Security is enhanced by increasing the number of keys and the scheme is also robust against attacks. Statistical simulations are also carried out for inspection the strength and viability of the algorithm.