Efficient Image Encryption and Decryption Using Discrete Wavelet Transform and Fractional Fourier Transform

We propose an algorithm that shows improvement in computation timeof existing image encryption-decryption methods. The algorithm also introduces additional one-level of encryption key into the existing methods. Image compression properties of the DWT (Discrete Wavelet Transform) are utilized to bring the improvement. The new algorithms retain MSE between input and decrypted images and the robustness of existing algorithms. We assume an image to be consisting of three primary color channels viz. R, G and B. An image is at first segregated into these channels and then these proposed methods compress input image channels by using DWT2 (2-D Discrete Wavelet Transform). The compressed image channels are encrypted using 2-D FRT (The 2-D fractional Fourier transform) and random phase masks in two successive steps. The encrypted channels are merged using IDWT2 (2-D Inverse Discrete Wavelet Transform), generating a color encrypted image. Decryption is the inverse of the encryption process. Simulations are performed and the results of these simulations verify the proposals made in the new algorithms.