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Hello,<br><br>Since I had some time and I both understand English and
French, I did an effort to translate the french non-technical
description of libdvdcss to English. You can find the text at the bottom
of this mail and, if your spambox allows, in attachment. Please keep in
mind that neither English nor French is my mothertongue.<br>I hope you can use it.<br><br>
<blockquote><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS">Non-technical description of libdvdcss
(v2.1)</font></p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS"><br></font>
</p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS"><br></font>
</p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS">Libdvdcss is a functions library a
program can use to explore the content of a DVD.</font></p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS"><br></font>
</p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS"><br></font>
</p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS">1/ The DVD "zones"</font></p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS"><br></font>
</p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS">All the commercial DVD's and DVD
players include "zone information". Due to this information
DVD's and DVD players are only useable in certain countries because
the zone information from the DVD player has to correspond with the
zone information from the DVD.</font></p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS"><br></font>
</p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS"><br></font>
</p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS">2/ The CSS</font></p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS"><br></font>
</p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS">The CSS (Content Scrambling System)
protects the large majority of the commercial DVD's. Software
developers for DVD player buy at the DVD CCA (DVD Copy Control
Association) keys to decrypt the CSS. At the same time they become
the user instructions of the CSS wich are kept secret.</font></p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS">Using his key, and while reading the
DVD, the software communicates with the DVD player to get the
decryption information.</font></p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS"><br></font>
</p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS"><br></font>
</p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS">/3 Copying the DVD</font></p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS"><br></font>
</p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS">This encryptions don't protect the DVD
from copying. It's possible making a physical copy working perfectly
the same (often called bit-to-bit) when using the right equipment.</font></p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS">And because the medium has to be
decrypted by the software from the DVD player to show the content on
the screen, this decrypted content is available during the lecture
regardless the used encryption.</font></p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS"><br></font>
</p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS"><br></font>
</p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS">4/ The weaknesses of CSS</font></p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS"><br></font>
</p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS">CSS had been the object of academic
studies wich have discovered how this jamming algorithm works, using
retro-analysis. Later, these studies have shown that the used CSS key
are cryptographically very weak wich has lead to more efficient
decryption algorithms and the discovery of the keys. It's possible
the obtain an exhaustive list on your home computer just in a few
minutes.</font></p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS"><br></font>
</p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS"><br></font>
</p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS">5/ How libdvdcss works</font></p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS"><br></font>
</p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS">This means the list of CSS keys is
perfectly known and a sample of these is distributed with libdvdcss.
Libdvdcss has the same behavior as a DVD player software and uses a
key of this sample. If all the keys from the sample fail, libdvdcss
calculates the rest of the keys and tries them.</font></p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS"><br></font>
</p><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS">It is possible that all this fails,
especially when DVD and DVD player are not in the same zone. As last
remedy, libdvdcss overrides the complete encryption and decrypts the
scrambled stream using the cryptographic weakness of CSS.</font></p><p style="margin-bottom:0cm"><br></p></blockquote><p style="margin-bottom:0cm"><font style="" face="Comic Sans MS"><font style="" face="Tahoma">Regards,</font></font></p><p style="margin-bottom:0cm"><br></p><font style="" face="Comic Sans MS"><font style="" face="Tahoma">Christopher</font></font> </div></body>
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