Watermarking for self-authentication of compressed video

This paper reports on watermarking of MPEG video for authentication and tamper detection. The algorithm operates entirely on the compressed bitstream and maintains MPEG-2 syntax throughout. In the proposed algorithm, I-frames watermark the entire length of the following GOP. The algorithm first computes the payload capacity of each GOP by identifying the population of eligible VLCs capable of carrying the watermarks. The candidate I-frame is then compressed to this target bit rate and the bits are reordered based on a GOP-unique key. The scrambled bits then sequentially watermark the GOP. Detection follows an inverse process. Watermarked video is resistant to tampering at the GOP level by observing the key sequencing needed for watermark extraction. Missing GOPs cause jumps in the required keys which can then be connected to the number of affected GOPs. Corruption or frame-level tampering inside a GOP can also be spotted using a similar approach.