Digital Content Protection Over Audio Return Data Link

A method comprising:

• authenticating a source device by a sink device using an authentication and encryption protocol;
• receiving, at the sink device, a data stream including audio data;
• encrypting at least a portion of the received audio data;
• packetizing the encrypted audio data including the at least the portion into sub-frames;
• modifying the sub-frames by inserting a first preamble code as a preamble of a sub-frame to indicate that rekeying is to be performed the source device according to the authentication and encryption protocol, and to indicate that at least the portion of the audio data in a payload of the sub-frame and payloads of a plurality of subsequent sub-frames is encrypted;
• and
• transmitting the modified sub-flames from the sink device to the source device via a first data link.

A non-transitory computer-readable storage medium storing executable computer instructions in a sink device, the instructions when executed by a processor causing the processor to:

• authenticate a source device by a sink device using an authentication and encryption protocol;
• receive a data stream including audio data;
• encrypt at least a portion of the received audio data;
• packetize the encrypted audio data including the at least the portion into sub-frames;
• modify the sub-frames by inserting a first preamble code as a preamble of a sub-frame to indicate that rekeying is to be performed at the source device according to the authentication and encryption protocol, and to indicate that the at least portion of the audio data in a payload of the sub-frame and payloads of a plurality of subsequent sub-frames is encrypted;
• and
• transmit the modified sub-frames to the source device via a first data link.