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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 proprietary 40-bit stream cipher algorithm. The system was introduced around 1996 and was first compromised in 1999. CSS is only 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 It has been superseded by newer DRM schemes such as Content Protection for Recordable Media (CPRM), or by Advanced Encryption Standard (AES) in the Advanced Access Content System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. ==Preliminary Note== 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,〔(DVD CCA CSS License Agreement )〕 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-〔(Standard ECMA-267, 3rd edition, 2001, 120 mm DVD - Read-Only Disk )〕 and MMC-〔(Multi-Media Commands - 5 (Working Draft) T10/1675D, Revision 4, 2006-10-24 )〕 specifications. There has also been some effort to collect CSS details from various sources.〔(The Content Scramble System – A Study )〕 Note that a DVD-Video can be produced with or without CSS. The publisher may for instance decide to go without CSS protection to save license and production costs. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Content Scramble System」の詳細全文を読む スポンサード リンク
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