A secure video system for a graphics display adaptor includes a module for decrypting a content signal from a media player or other secure content source. The adaptor may be provided as a component of a computer graphics system, or in a stand-alone special-purpose device. The adaptor may include other features for preventing unauthorized use of protected content, for example authenticating the source of a content signal before providing an output audio or video signal, encrypting the output video signal, responding to commands to renew or revoke cryptographic keysets, and embedding forensic tracking information in an audio or video signal.