Lightweight chaos-based cryptosystem for secure images

In the last two decades, several chaos-based cryptosystems have been proposed. Some of them have architecture comprising a layer of permutation and a layer of diffusion and these layers are simultaneously executed in a simple scan of plain-image pixels. In this kind of cryptosystems, due to the channel effect, a bit error(s) in the cipher-image produces, at the decryption side, a random bit error in the estimated plainimage. In this paper, we propose a cipher-block encryption algorithm in CBC (Cipher Block Chaining) mode. It consists of a permutation process on the bits achieved by a 2D-cat map, followed by a bitwise XOR operation. Here, each permuted bit (confusion phase) is immediately diffused in a simple manner in the same phase. Therefore, the confusion and diffusion effects are stronger and the cryptanalyses for permutation-only ciphers become ineffective.