Every time I see HDCP's digital protection technology, I think about HDMI and DVI. Nowadays, two kinds of transmission devices that are commonly used are everywhere. Then, where is the digital protection technology added? Some people say that it is added to the HDMI cable and Inside the DVI line, there is still a description inside the interface, and then there are more in the DVI fiber extender. In fact, HDCP technology has been protected during the entire transmission of audio and video content, as described below.
For example, on a computer platform, when the audio and video content protected by HDCP technology is output, the COPP (Certified Output Protection Protocol) driver in the Microsoft operating system first verifies the graphics card, and only the graphics card supporting HDCP can realize the output of the content; The system will authenticate the key of the display device, and only the HDCP-compliant device can finally display the video and audio content transmitted by the video card.
During the entire transmission process, both the transmitting end and the receiving end store an available key set, which are secretly stored, and the transmitting end and the receiving end perform encryption and decryption operations according to the key. A special value is added to the encryption and decryption operation - KSV (KeySelectionVector). Each device that supports HDCP will have a unique KSV serial number. The cryptographic processing unit at the sender and receiver will check the KSV value of the other party to determine that the connection is legitimate. The detailed process is as follows: the sender will generate a 64-bit pseudo-random sequence An from its own cryptographic engine and send it to the receiver simultaneously with its own KSV. The receiver will then feed back to its own KSV and Repeater bits. Both KSVs must conform to the correct format and consist of 20 0s and 20s. The cryptographic processing unit at the transmitting end and the receiving end independently calculate the values of the respective R0, Mo, and Ks, and then compare the two R0 values, and only pass the authentication if the two completely match.
During the encryption process, HDCP processes each pixel to make the picture irregular and unrecognizable. Only the sender and the receiver after the mutual authentication synchronization (?) can perform the decryption operation and restore the data. No information was found on the encryption method used by HDCP for research.
Through HDCP's explanation, we can learn more about the protection encryption technology. This technology has brought great effects to our audio and video industry. In order to ensure that high-definition signals transmitted by HDMI or DVI will not be illegally recorded, HDCP technology has emerged. The HDCP specification is led by Intel. When users illegally copy high-definition signals, the technology will interfere and reduce the quality of the copied images to protect the content.