content protection for prerecorded media (copy protection) (CPPM)
Content Protection for Prerecorded Media (CPPM) is a method for copy protection of recorded audio media, such as DVD-Audio. It was developed by the 4C group consisting of Intel, IBM, Matsushita and Toshiba and uses a 56-bit key for encryption.
The CPPM specifications define a renewable encryption method that can be used to protect audio content when it is stored on physical media. CPPM acts as a content scramblingsystem( CSS), but uses 56 bits rather than 40 bits.
In CPPM decryption, the encrypted audio data, the Copy Control Information( CCI) and the Media Block Key (MBK) are transferred from the DVD-Audio to the CPPM decrypter, which uses them in combination with the Player Device Key to decrypt the audio.