Sketch attacks: A note on designing video encryption method in H.264/AVC

In this work, we propose four sketch attacks on H.264/AVC encrypted-compressed video. First, we briefly describe the notion of sketch attack, then deploy the conventional sketch attacks, which are designed for still image, to sketch the frames of H.264/AVC compressed video. Next, we propose four sketch attacks to generate outline of the original frame by using partially decoded information of the H.264/AVC compressed video, including residue DC coefficients, residue AC coefficients, motion vectors, and macroblock bitstream size. Experiments are conducted to verify the performance of the proposed sketch attacks using the ICADR2013 and HEVC dash video data sets. The proposed sketch attacks are also compared with the four conventional sketch attacks. Results indicate that the proposed sketch attack can generate the outline of a frame regardless of its type, where the fidelity of the sketch image improves as resolution increases.