Antiforensic synthesis of motion vectors using template algorithms

The identification of the video camera employed to acquire a video sequence is made possible by a large set of different footprints. Since video signals are always available in a compressed format, some of the most significant traces can be related to the coding tools of the implemented video codec (e.g., rate-distortion optimization, motion estimation strategy, etc.). As a matter of fact, an effective antiforensic attack, which aims at fooling the tools that identify the acquisition device, must appropriately alter these footprints. In the paper, we present an antiforensic strategy that targets a video camera detector which is based on the identification of the motion estimation strategy used by the video coder. The proposed approach synthesizes a set of motion vectors that approximate those that would have been generated by the algorithm to be mimicked. This method proves to be effective in attacking the detector while preserving the coding efficiency.