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In The HDCP 2.2 Authentication Process – an Introduction, we discussed why we need HDCP, and the basic steps of the HDCP Authentication Process. We noted that an advanced version of RSA is the underlying cryptography standard used during the Authentication and key exchange. In HDCP 2.2 Authentication: RSA Cryptography, we discussed the basics of RSA Cryptography. In this blog post, we will dive into the details of Authentication and Key Exchange (AKE), which is the first step in the authentication protocol.

The HDCP transmitter can start at any time even before a previous authentication is complete. HDCP Receiver’s public key Certificate is verified by the HDCP transmitter then the devices share a master key Km. This stored master Key Km accelerates the subsequent communication between HDCP transmitter and Receiver. Authentication also happens even if the transmitter doesn’t have a stored master Key corresponding to the HDCP receiver. These keys information are sent in form of messages. If we are using HDMI then these messages would go over the I2C based control bus in big endian format.

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