High-Bandwidth Digital Content Protection (HDCP) is required for secure transmission of video data. The AUX FIFO interface is used by the DP TX controller to forward information from the receiver (sink) or repeater device, and responses from the HDCP controller are sent back to the receiver/repeater. This interface is critical for receiving configuration data as well as for completing the authentication and key exchange before encrypted video can be transmitted over the channel. The keystream port is used to send the key information which the DP TX combines with the video data to create encrypted streams.
The entropy interface is used to send a 128b nonce generated by the TRNG, which is used as the seed for key generation by the HDCP controller. The identity interface is used to transmit a platform key to the HDCP controller.