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On 21/04/12 15:10, Crocy . wrote:
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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>
</div>
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Hi Cristophe,<br>
<br>
I've made a few changes to the translation (see inline).<br>
For reference, the original is at
<a class="moz-txt-link-freetext" href="http://www.videolan.org/developers/libdvdcss.txt">http://www.videolan.org/developers/libdvdcss.txt</a><br>
<br>
Best regards<br>
<br>
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<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">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">1/ The DVD "zones"</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>
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<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">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.</font></p>
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<p style="margin-bottom:0cm"><font style="" face="Comic Sans
MS">At the same time they become
the user instructions of the CSS wich are kept secret.</font></p>
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At the same time they obtain the instructions to use the CSS, which
are kept secret.<br>
<br>
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<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">/3 Copying the DVD</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>
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These <font style="" face="Comic Sans MS">encryptions don't protect
the DVD
from being copied. U</font><font style="" face="Comic Sans MS">sing
the right equipment, i</font><font style="" face="Comic Sans MS">t's
possible to make a physical copy </font><font style=""
face="Comic Sans MS">(often called bit-to-bit) </font><font
style="" face="Comic Sans MS">which works exactly
the same as the original one.</font>
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<p style="margin-bottom: 0cm;"><font style="" face="Comic Sans
MS">And because the medium </font></p>
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Moreover, as the medium<br>
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<p style="margin-bottom:0cm"><font style="" face="Comic Sans
MS">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">4/ The weaknesses of CSS</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.</font></p>
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CSS has been the subject of <font style="" face="Comic Sans MS">
academic
studies which have discovered how this jamming algorithm works,
using
reverse engineering.</font>
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<p style="margin-bottom:0cm"><font style="" face="Comic Sans
MS"> 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>
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Later, these <font style="" face="Comic Sans MS">studies have shown
that the keys used by CSS
are cryptographically very weak, leading 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.<br>
<br>
</font>
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<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">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">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>
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