It has been superseded by newer DRM schemes such as Content Protection for Recordable Media (CPRM), or by Advanced Encryption Standard (AES) in the Advanced Access Content System (AACS) DRM scheme used by HD DVD and Blu-ray Disc, which have 56-bit and 128-bit key sizes, respectively, providing a much higher level of security than the less secure 40-bit key size of CSS.
The content scramble system (CSS) is a collection of proprietary protection mechanisms for DVD-Video discs.
According to the DVD Copy Control Association (CCA), which is the consortium that grants licenses, CSS is supposed to protect the intellectual property rights of the content owner.
The license,[2] which binds the licensee to a non-disclosure agreement, would not permit the development of open-source software for DVD-Video playback.
Circumvention of regional protection is not possible with every drive—even if the drive grants access to the feature, prediction of title keys may fail.
However, if the drive detects a disc that has been compiled with CSS, it denies access to logical blocks that are marked as copyrighted (§6.15.3[4]).
RPC Phase II drives hold an 8-bit region-code and adhere to all requirements of the CSS license agreement (§6.29.3.1.7[4]).
It appears that RPC Phase II drives reject title-key requests on region mismatch.
At the time CSS was introduced, it was forbidden in the United States for manufacturers to export cryptographic systems employing keys in excess of 40 bits, a key length that had already been shown to be wholly inadequate in the face of increasing computer processing power (see Data Encryption Standard).
Ethan Hawke presented a plain-text prediction for data repetitions in the MPEG program stream that enables the recovery of title-keys in real-time directly from the encrypted DVD-Video.
", a claim cited as originating from personal communication with an anonymous source; Nelson is the author of Computer Lib.