It is likely that these terms refer to a combination of technical processes rather than a single document. Understanding the Components
The process begins by parsing the MPD file to find the block. The PSSH string is typically base64-encoded. Tools or scripts decode this string to extract the Key ID (KID), which uniquely identifies the cryptographic key used to lock the video. 2. The License Request (The Handshake)
The CDM simulates a secure handshake with the license server.