JPEG Image Encryption With Adaptive DC Coefficient Prediction and RS Pair Permutation

JPEG image encryption aims at effectively converting the original JPEG image into a noise-like image that does not contain any useful information of original image. Existing schemes for JPEG image encryption, however, may not attain a good balance in terms of file size increment and encryption security. To address the problem, we design a novel JPEG image encryption scheme. Different from existing schemes, we first predict DC coefficients by an adaptive prediction method. Subsequently, the histogram of DC coefficient prediction errors is encrypted by combining the prediction errors and random integers to reduce the encoded length, which can ensure a very small increment of file size. Furthermore, we construct the RS (run/size) pairs in each DCT block and then implement the permutation for both RS pairs extracted from the upper left corner of each DCT block and all DCT blocks excluding DC coefficients, which can further distort the image contents. Extensive experiments demonstrate that, compared with existing JPEG image encryption schemes, our scheme can ensure not only the JPEG format compatibility for encrypted image, but also keep a very small file size increment and the superior security performance.