In authentication using watermarking, the original media needs to be slightly modified in order to embed a short media digest in the media itself. Lossless authentication watermark achieves the same goal with the advantage that the distortion can be erased if media authenticity is positively verified. In this paper, we extend lossless data embedding methods originally developed for the JPEG image format to digital video in the MPEG-2 format. Two new lossless watermarking methods for authentication of digital videos are presented. In the first approach, each frame contains its hash embedded losslessly, while in the second approach we embed a hash of a group of frames in B frames only. Implementation issues, such as real-time performance, are also addressed.