An Image Encryption Scheme Based on Permutation-subsitution Architecture at Half Pixel Level

An image encryption scheme using permutation-substitution mechanism at half pixel level is proposed. One round of permutation and one round of substitution achieve desirable results. In the permutation process, the image sized HxW is expanded to one sized Hx2W. The generalized Arnold map is applied to generate the pseudo-random sequences for the permutation and substitution processes implemented row-by-row/column-by-column instead of pixel-by-pixel to increase the encryption rate. The security and performance of the proposed scheme have been analyzed as well.