Patent ID: 8656183

Claim:
A method of decoding encrypted content using a playback device on which an active user encryption key is stored, where the content includes frames of video and at least a portion of a plurality of frames of video are encrypted using at least one frame encryption key, and the at least one frame encryption key is encrypted using a content encryption key, and copies of the content encryption key are separately encrypted using a plurality of different user encryption keys including the active user encryption key, the method comprising: obtaining encrypted content using a playback device, where the content includes frames of video and at least a portion of a plurality of frames of video are encrypted using at least one frame encryption key; obtaining using the playback device a copy of the at least one frame encryption key that is encrypted using a content encryption key and copies of the content encryption key that are separately encrypted using a plurality of different user encryption keys including an active user encryption key stored on the playback device; determining using the playback device which of the encrypted copies of the content encryption key was encrypted using the active user encryption key stored on the playback device; decrypting the identified copy of the content encryption key using the playback device and the active user encryption key; decrypting the at least one frame encryption key using the playback device and the decrypted content encryption key; playing back frames of the encrypted content using the playback device, where playing back frames of the encrypted content further comprises: identifying any portions of a frame that are encrypted; identifying the frame encryption key used to encrypt the identified portions of the frame; decrypting the encrypted portions of the frame using the identified frame encryption key; and decoding the unencrypted frame of video.