Digital content protection over audio return data link

1. A sink device comprising:

a receiver configured to receive a data stream including audio data;

an encryption engine coupled to the receiver, the encryption engine comprising a processor and a memory, the processor configured to:

authenticate a source device using an authentication and encryption protocol, the source device configured to send video data to the sink device,

encrypt the received audio data,

packetize the encrypted audio data into sub-frames, and

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, the first preamble code further indicating that the audio data in a payload of the sub-frame and payloads of a plurality of subsequent sub-frames is encrypted; and

a transmitter coupled to the encryption engine, the transmitter configured to transmit the modified sub-frames to the source device via a first data link.

2. The sink device of claim 1 , wherein the audio data comprises a plurality units of audio blocks, each audio block comprising 192 frames, each frame comprising 2 sub-frames, and each sub-frame comprising at least a preamble and an audio sample word.

3. The sink device of claim 2 , wherein the preamble includes one of: the first preamble code, a second preamble code indicating a start of an audio block and that an audio sample word corresponding to a first channel is to follow, a third preamble code indicating that an audio sample word corresponding to the first channel is to follow, and a fourth preamble code indicating that an audio sample word corresponding to a second channel is to follow.

4. The sink device of claim 3 , wherein the first preamble code further indicates a start of an audio block and that an audio sample word corresponding to the first channel is to follow.

5. The sink device of claim 3 , wherein the encryption engine inserts the first preamble code as the preamble of the sub-frame by at least replacing a second preamble code of the preamble of the sub-frame with the first preamble code.

6. The sink device of claim 1 , wherein the encryption engine is further configured to determine whether a portion of the audio data is to be encrypted, encrypt the portion of the audio data, and packetize the encrypted portion into sub-frames.

7. The sink device of claim 1 , wherein the first data link is an Audio Return Channel (ARC).

8. The sink device of claim 7 , wherein the source device is authenticated by the sink device is performed via the first data link.

9. The sink device of claim 1 , wherein the source device is authenticated using the first data link and a second data link separate from the first data link.

10. The sink device of claim 9 , wherein the second data link is a Display Data Channel (DDC), and the authentication and encryption protocol is High-bandwidth Digital Content Protection (HDCP) protocol.

11. A method comprising:

authenticating a source device by a sink device using an authentication and encryption protocol, the source device configured to send video data to the sink device;

receiving, at the sink device, a data stream including audio data;

encrypting the received audio data;

packetizing the encrypted audio data 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 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-frames from the sink device to the source device via a first data link.

12. The method of claim 11 , wherein the audio data comprises a plurality units of audio blocks, each audio block comprising 192 frames, each frame comprising 2 sub-frames, and each sub-frame comprising at least a preamble and an audio sample word.

13. The method of claim 12 , wherein the preamble includes one of: the first preamble code, a second preamble code indicating a start of an audio block and that an audio sample word corresponding to a first channel is to follow, a third preamble code indicating that an audio sample word corresponding to the first channel is to follow, and a fourth preamble code indicating that an audio sample word corresponding to a second channel is to follow.

14. The method of claim 13 , wherein the first preamble code further indicates a start of an audio block and that an audio sample word corresponding to the first channel is to follow.

15. The method of claim 13 , wherein inserting the first preamble code as the preamble of the sub-frame comprises:

replacing a second preamble code of the preamble of the sub-frame with the first preamble code.

16. The method of claim 11 , further comprising:

determining whether a portion of the audio data is to be encrypted,

wherein encrypting the received audio data comprises encrypting the portion of the audio data, and

wherein packetizing the encrypted audio data into sub-frames comprises packetizing the encrypted portion into sub-frames.

17. The method of claim 11 , wherein the first data link is an Audio Return Channel (ARC).

18. The method of claim 17 , wherein authenticating of the source device by the sink device is performed via the first data link.

19. The method of claim 11 , wherein authenticating of the source device by the sink device is performed via the first data link and a second data link separate from the first data link.

20. The method of claim 19 , wherein the second data link is a Display Data Channel (DDC) and the authentication and encryption protocol is High-bandwidth Digital Content Protection (HDCP) protocol.

21. 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, the source device configured to send video data to the sink device;

receive a data stream including audio data;

encrypt the received audio data;

packetize the encrypted audio data 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 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.