抵抗共谋攻击的运动一致性空域视频水印

Spatial Domain Video Watermarking with Motion Coherence against Collusion Attacks

运动补偿时域帧平均(MC-TFA)共谋攻击利用时域上的冗余来去除时域不相关的水印,这对视频水印提出了运动一致性的要求,即水印需要随着视频的运动而做相应的变化。本文提出一种可有效抵抗MC-TFA攻击的空域视频水印。对原始视频做基于宏块的运动估计得到运动矢量,据此对原始水印进行以宏块为单位的移位调整得到嵌入水印。因为嵌入水印和原始视频的运动矢量是一样的,所以它具有运动一致性。本文接着证明了嵌入运动一致性水印不会影响视频的运动矢量,因此在检测端对加水印的视频做运动估计就可以得到与嵌入水印之前一样的运动矢量,从而恢复出所嵌入的水印,最后用归一化相关系数的方法来检测其中是否含有水印。该方法能与MPEG编码器结合且算法简单,实验结果表明它能够有效抵抗MC-TFA攻击。此外,该水印嵌入方法的运动一致性通过P.Vinod等人提出的方法进一步得到了验证。

Robustness to collusion attack is one of the most challenging issues in video watermarking.The motion compensated temporal frame averaging（MC-TFA） attack removes the temporal uncorrelated watermark by exploiting the temporal redundancy among consecutive frames.In order to address this problem,a motion coherent video watermark,which changes according to the motion in the video frames,is needed.In this paper,we propose a novel watermarking scheme that can effectively combat the MC-TFA attack.The method relies on the macroblock-based motion estimation,which conforms to the MPEG compression standards.A motion coherent watermark is generated according to the obtained motion vectors,and embedded into the video frame in the spatial domain.We also prove that embedding motion coherent watermark will not affect the motion vectors of the video,which make it possible to extract the embedded watermark from a watermarked video in the detector,without the need of the original video.Normalized correlation is then calculated to determine whether the received video contains a particular watermark.Experiments show the effectiveness of our method.Besides, the motion coherency of the watermark is further verified by the method provided by P.Vinod et al.