A secure block operation based bit-plane image encryption using chaotic maps

This paper proposes a scheme for image encryption based on fixed block operations of size $2\times 2$. The proposed scheme encrypts images of any sizes. This technique addresses the problem of executing fixed block based permutations and diffusions in variable-sized images. For fixed block size based operation, the proposed method initially generates eight bit-planes and then combines bit-planes into two groups, where each group has four bit-planes. The combined bit-planes are then divided into blocks of size $2\times 2$. Then the array of two groups of blocks are permuted by using two different Piece-wise Linear Chaotic Map (PWLCM) systems independently. After block permutation, the block diffusion (bit-XOR) is performed by using a key block generated by another PWLCM system. Finally, the diffused blocks are combined to generate a cipher image, which is same size of original image. Apart from that, the proposed algorithm uses the plaintext related keys to resist the ciphertext against the major type of attacks known as 'known-plaintext attack (KPA)' and 'chosen-plaintext attack (CPA) The computer simulations show the best performance of the algorithm on encryption of images of variable sizes. The security evaluation ensures that the algorithm proposed is resistive to several widely used attacks.