Abstract: Method and apparatus for watermarking digital video material by embedding a digital signature. One embodiment of the system integrates the embedding procedure into a block-based compression scheme. In one embodiment, a 32-bit digital signature is embedded into the x- and y-coordinates of motion vectors. Since not all motion vectors are suitable for coding (with regard to objectionable visible artifacts), three hybrid selection criteria have been developed for determining whether or not to code a motion vector. A probabilistic coding procedure has also been developed to avoid problems that arise when fewer than 16 blocks and/or vectors (where 16 vectors correspond to 32 bits) can be coded in a frame. One such procedure makes use of binary random sequences to virtually code the signature into the motion vectors. The system has been implemented on a CRAY T3D massively parallel supercomputer, where a near-real-time (5 frames per second) embedding of the signature is obtainable.