Content-scrambling system
| General | |
|---|---|
| Designers | DVD Forum |
| First published | 1996 |
| Certification | DVD Copy Control Association |
| Cipher detail | |
| Key sizes | 40 bits |
| Security claims | 240 |
| State size | 2048 bytes (DVD sector size) |
| Structure | Stream cipher |
| Best public cryptanalysis | |
| Defeated in 1999 by DeCSS, 40-bit key size is subject to brute-force attack, effective key size is about 16 bits. This can be brute-forced in about a minute by a Pentium II. | |
The Content Scramble System (CSS) is a digital rights management (DRM) and encryption system employed on many commercially produced DVD-Video discs. CSS utilizes a 40-bit stream cipher algorithm. The system was introduced around 1996 and was first compromised in 1999.
CSS is one of several complementary systems designed to restrict DVD-Video access.
It has been superseded by newer DRM schemes such as Content Protection for Recordable Media (CPRM), or by Advanced Encryption Standard (AES) in the Advanced Access Content System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. CSS attempts to restrict access to the content only for licensed applications. 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 details of CSS are only given to licensees for a fee. The license, which is bound to a non-disclosure agreement, wouldn't permit the development of open-source software for DVD-Video playback. Instead, there is libdvdcss, a reverse engineered implementation of CSS. Libdvdcss is an invaluable source for documentation, along with the publicly available DVD-ROM- and MMC- specifications. There has also been some effort to collect CSS details from various sources.
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