A New Algorithm of Encryption and Decryption of Images Using Chaotic Mapping

The combination of chaotic theory and cryptography forms an important field of information security. In the past decade, chaos based image encryption is given much attention in the research of information security and a lot of image encryption algorithms based on chaotic maps have been proposed. Due to some inherent features of images like bulk data capacity and high data redundancy, the encryption of images is different from that of texts; therefore it is difficult to handle them by traditional encryption methods. In this communication, a new image encryption algorithm based on three different chaotic maps is proposed. In the proposed algorithm, the plain-image is first decomposed into 8x8 size blocks and then the block based shuffling of image is carried out using 2D Cat map. Further, the control parameters of shuffling are randomly generated by employing 2D coupled Logistic map. After that the shuffled image is encrypted using chaotic sequence generated by onedimensional Logistic map. The experimental results show that the proposed algorithm can successfully encrypt/decrypt the images with same secret keys, and the algorithm has good encryption effect, large key space and high sensitivity to a small change in secret keys. Moreover, the simulation analysis also demonstrates that the encrypted images have good information entropy, very low correlation coefficients and the distribution of gray values of an encrypted image has random-like behavior. Keywords—Information security, image encryption, chaotic maps, image shuffling, logistic map, information entropy.