A novel robust dual diffusion/confusion encryption technique for color image based on Chaos, DNA and SHA-2

In the proposed article, a novel way of confusion is designed by introducing intra-permutation and Exclusive-OR operation with complementary DNA rules that bringsrandomness in the image. A SHA-256 hash function is used for modification of the initial conditions for 2-Dimensional Logistic map. In the 1st phase of diffusion, the rows of the three colored channels are exchanged by selecting DC-Boxes chaotically and then same operation is applied on the columns. In 2nd diffusion phase, each color channel is permuted independently using chaotic sequence. Before confusion, DNA encoding is applied at pixel level chaotically and transformed each color channel into a linear array. These three arrays are combined into a matrix of three rows and multiple columns. This matrix is divided into blocks; each of size of three DNA bases; one from each color channel and substituted by Intra-channel diffusion using DC-Boxes. In 2nd phase of confusion, matrix is transformed into a large 1D array representing DNA bases of a color image. This large array is split into groups of size of four DNA bases; representing a pixel. These groups are substituted by Exclusive-OR operation with DNA complementary rules thatselected chaotically. The proposed algorithm requires only single round of confusion/diffusion operationto achieve high quality of encryption results. This scheme is quite different for color image encryption based on DNA and has better results for different tests like NPCR, UACI, information entropy etc. Besides the larger key space, resistance against common transmission noise is another significant advantage of proposed scheme over some existing systems.