T Gopalakrishnan and S Ramakrishnan: Image Encryption in Block-wise with Multiple Chaotic Maps for Permutation and Diffusion

This paper presents an efficient block-wise image encryption method based on multiple chaotic maps. The image is divided into four overlapping blocks and each block is permutated with Cat map and its parameters are controlled by Henon map using multiple keys. Due to overlapping division of blocks, it produces effect of double permutation in the middle portion of overlapped image in single permutation itself. For diffusion, the whole image is divided into four non-overlapping blocks and diffused with logistic map. Each block pixel values were completely modified in the diffusion process in order to avoid knownplaintext and chosen-plaintext attacks. For each division of blocks different keys were selected for both permutation and diffusion process in the proposed method. The simulation results of several statistical analysis shows that the proposed cryptosystem is efficient and highly secured.