A scrambling framework for block transform compressed image

In this work, we propose a scrambling framework for block transform compressed image. First, three attacks are proposed to sketch the outline of the original image directly from its scrambled counterpart by exploiting information deduced from the transformed components. Based on the proposed sketch attacks, a scrambling framework aiming to minimize the bitstream size overhead and prevent the leakage of visual information is put forward. In particular, the DC components are manipulated within each non-overlapping region to achieve the scrambling while simultaneously reducing the bitstream size overhead. The non-DC components are shuffled and substituted to generate a completely distorted image while preventing information leakage. The ideas are implemented in JPEG to verify its performance and compare to that of the conventional JPEG based scrambling methods. Results indicate that the proposed methods exhibit stable performance in terms of the bitstream size overhead when using different quality factors, and it is able to withstand the proposed sketch attacks as well as the classical cryptographic attacks.