Image encryption strategy transparent to transcoding

A new encryption strategy proposed in this paper, which based on duple permutation, is designed for transparent transcoding. Firstly the original image is divided into several macro blocks by certain size, and the sequence of macro block rows is reordered. Then, the macro blocks are permuted in rows. Theoretical analysis and experimental results indicate that the strategy proposed in this paper is transparent to transcoding, security and low computation complexity. It has little adverse impact on the compact ratio. All the attributes mentioned above make this strategy suitable to be the encryption approach for image transmission.