Early content engine receiver synchronization
An HDCP receiver device that receives frames from an HDCP transmitter device. The receiver device has a frame counter that is updated for each frame that is received from the transmitter device and that includes encrypted content, while the receiver device is in a pre-authorization mode. During the pre-authorization mode, the receiver device does not decrypt any received frame bearing encrypted content. While the receiver device waits to transition from the pre-authorization mode to a post-authorization mode in which the receiver device can begin to decrypt any received frames that include encrypted content, the frame counter is updated for each frame received that includes encrypted content. In the post-authorization mode, the frame counter has a nonzero value if frames including encrypted content were received by the receiver device during the pre-authorization mode.
1. A hardware receiver device operating in a pre-authorization mode and a post-authorization mode, the receiver device comprising:
an interface port that receives frames from a transmitter device;
a content encryption engine (CEE) having an output port; and
a frame counter having a frame counter value and an input port coupled to receive a control signal from the output port of the CEE, the control signal indicating the presence of encrypted content within the received frames, the frame counter value being incremented by the CEE for each of the frames received during the pre-authorization mode from the transmitter device that include the encrypted content, such that in the post-authorization mode, the frame counter value is nonzero if the frames received during the pre-authorization mode included the encrypted content;
wherein the receiver device does not decrypt the received frames in the pre-authorization mode while waiting to transition from the pre-authorization mode to the post-authorization mode, wherein the pre-authorization mode is a state of the receiver device before a session key exchange has been completed with the transmitter device and the post-authorization mode is a state of the receiver after the session key exchange has been completed, and
wherein the receiver device uses the frame counter value to synchronize decrypting of the encrypted content.
2. The receiver device of claim 1 , wherein:
the CEE waits for completion of the session key exchange before decrypting the received frames that include the encrypted content.
3. The receiver device of claim 1 , wherein the CEE outputs a temporary image while encryption keys associated with the session key exchange are being programmed.
4. The receiver device of claim 1 , wherein the frame counter is implemented by an Advanced Encryption Standard engine running in counter mode that increments the counter value each time one of the received frames includes encrypted content.
5. The receiver device of claim 1 , wherein the receiver device receives the frames from the transmitter device according to the High-bandwidth Digital Content Protection (HDCP) on High Definition Multimedia Interface (HDMI) 2.2 specification.
6. The receiver device of claim 1 , wherein the frame counter does not begin incrementing until a frame, from among the received frames, includes the encrypted content received.