A video signal authentication system utilizes selected portions of a video signal to generate authentication codes that are transmitted in association with respective portions of the signal. The video signal preferably is in compressed format and includes synchronizing codes. The data between synchronizing codes preferably is used as discreet portions of the video signal. Each discreet portion is utilized with a selectively known key and a hash-based authentication code generating strategy to generate an authentication code. Each video portion preferably has its own authentication code. The authentication code is appended to the portion of the video signal and transmitted from a first location to the second location. At the second location, the same authentication code generating strategy is performed on the received portion of video data to generate a received authentication code. The transmitted authentication code is then compared to the received authentication code to verify the authenticity of the transmitted portion of the video signal.