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Remove confusing and probably wrong paragraph about libdvdcss. 

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@20442 b3059339-0415-0410-9bf9-f77b7e298cf2
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diego 2006-10-25 12:08:28 +00:00
parent a0618fd310
commit a60574bcbb
1 changed files with 1 additions and 58 deletions
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59
DOCS/xml/en/cd-dvd.xml
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@ -181,67 +181,10 @@ are dynamically allocated.
<para>
DVD decryption is done by <systemitem>libdvdcss</systemitem>. The method
can be specified through the <envar>DVDCSS_METHOD</envar> environment
variable, which can be set to key, disk or title.
variable, see the manual page for details.
</para>
</formalpara>
<para>
If nothing is specified it tries the following methods (default: key,
title request):
</para>
<orderedlist>
<listitem><para>
<emphasis role="bold">bus key</emphasis>: This key is negotiated during
authentication (a long mix of ioctls and various key exchanges, crypto
stuff) and is used to encrypt the title and disk keys before sending them
over the unprotected bus (to prevent eavesdropping). The bus key is needed
to get and predecrypt the crypted disk key.
</para></listitem>
<listitem><para>
<emphasis role="bold">cached key</emphasis>: <application>MPlayer</application>
looks for already cracked title keys which are stored in the
<filename class="directory">~/.dvdcss</filename> directory (fast).
</para></listitem>
<listitem><para>
<emphasis role="bold">key</emphasis>: If no cached key is available,
<application>MPlayer</application> tries to decrypt the disk key with a set
of included player keys.
</para></listitem>
<listitem><para>
<emphasis role="bold">disk</emphasis>: If the key method fails
(e.g. no included player keys), <application>MPlayer</application>
will crack the disk key using a brute force algorithm. This process
is CPU intensive and requires 64 MB of memory (16M 32Bit entries hash
table) to store temporary data. This method should always work (slow).
</para></listitem>
<listitem><para>
<emphasis role="bold">title request</emphasis>: With the disk key
<application>MPlayer</application> requests the crypted title keys,
which are inside <emphasis>hidden sectors</emphasis> using <systemitem>ioctl()</systemitem>.
The region protection of RPC-2 drives is performed in this step and may fail on such drives.
If it succeeds, the title keys will be decrypted with the bus and disk key.
</para></listitem>
<listitem><para>
<emphasis role="bold">title</emphasis>: This method is used if the title
request failed and does not rely on any key exchange with the DVD drive.
It uses a crypto attack to guess the title key directly (by finding a
repeating pattern in the decrypted VOB content and guessing that the
plain text corresponding to the first encrypted bytes is a continuation
of that pattern). The method is also known as &quot;known plaintext attack&quot;
or &quot;DeCSSPlus&quot;. In rare cases this may fail because there is not
enough encrypted data on the disk to perform a statistical attack or because
the key changes in the middle of a title. This method is the only way to
decrypt a DVD stored on a hard disk or a DVD with the wrong region on an
RPC2 drive (slow).
</para></listitem>
</orderedlist>
<para>
RPC-1 DVD drives only protect region settings through software. RPC-2 drives
have a hardware protection that allows 5 changes only. It might be