[svlug] Encrypted Blu-Rays (was: ubuntu 14.04 where are the wifi tables stored?)

Rick Moen rick at svlug.org
Mon Jan 19 13:57:03 PST 2015


I wrote:

> The point is, those are different problems.

In fact, playing encrypted Blu-Rays in effect requires solving both problems
consecutively:  

(a) Mounting the UDF filesystem from the Blu-Ray mass-storage device.  This
could be a problem if your kernel and mount utiltiies lack support for UDF,
or if they support only UDF 2.0 partitions and the movie Blu-Ray happens to
be on UDF 2.5.

(b) Use some sort of software able to work through the AACS Digital
Restrictions Management that Our Lords in Hollywood use to handcuff their
movie files.  This includes the player key (aka device key) that each
Blu-Ray drive insists on receiving form the accessing software and
re-validating to see if Our Lords in Hollywood have retroactively revoked
it.  The validated player key then gets used to decrypt the disc's unique
volume key (aka title key), which in turn is then used to decrypt the movie
file itself.  (Any unrevoked player key will do.  It doesn't have to be the
one for your drive hardware.)

Volume keys to many common movies have been discovered and are widely
distributed, such that, for example, recent movie-playing software on Linux
can play those movies even without a player key.


The decryption can be performed inline by the player software _or_ done
separately to allow dumping a 50GB or so unencrypted movie file to your hard
disk so you don't have to remain tied to the optical disc only (nor be
subject to artificial region restrictions, be banned from fast-forwarding
through legal notices and advertisements, or be banned from sending output
to non-HDCP-handcuffed video cables without a 75% cut to screen resolution).
The DumpHD utility can do that, for example, if fed the volume key.

Some Blu-Rays use a particularly nasty form of Digital Restrictions
Management called BD+, which can likewise be decrypted but requires later
tools than DumpHD.


Anyway, the _first_ thing to do is verify that you can mount the UDF volume
from the movie Blu-Ray.  If you can't, then filesystem support is your
immediate obstacle.




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