DVD Copy Protection
Digital Copy Protection
The Content Scrambling System (CSS) is used to
scramble the audio/video data on a DVD-Video disc. Each video title set
(VTS) can be selectively scrambled using a unique key. Each unique title
is assigned one Disc Key and up to 99 Title Keys (one per VTS), which are
stored on the disc in encrypted form. In the decoder, the original keys
are obtained by decryption and used to descramble the data. Only the video
data is encrypted. For DVD-ROM drives, the MPEG-2 decoder challenges the
drive and receives the necessary keys for decryption. This ensures that
only approved hardware/software can be used.
The keys used should be unique for every disc
title and are encrypted by the CSS Licensing Authority and, usually, the
scrambling is carried out during glass mastering. Security is vital and
the keys used plus the encryption algorithms must be kept secret. Only
those companies involved in designing hardware and software for CSS
encoding and/or decoding need information on the algorithms and systems
used. DVD Analogue Copy Protection
The Macrovision Analogue Protection System (APS)
is based on Macrovision version 7.0 and is used to distort the composite
video output to prevent recording and playback on VHS. This does not
extend to RGB or YUV outputs for which new methods are required and are
currently being investigated.
Adding APS to a DVD-Video disc requires the
content owner to become licensed by Macrovision and the authoring studio
to set a flag to enable APS in the player. |
