APC_Australia_Issue_442_June_2017

through S/PDIF’ with SMPLayer)
under Sound Options. (If you have a
cheap sound card, you might be out
of luck, sorry.)
EVIL ENCRYPTION
So what makes Blu-ray so hard to
support, and why can’t we just crack
its encryption the way we eventually
did with DVD? Jean-Baptiste from
the VideoLAN team: “Blu-ray is quite
complex to support, for two major
reasons: DRM and Interactive Menus.
The video part of the Blu-ray is not that
hard to do, since it’s regular codecs,
but the packaging is very complex
to handle.
“Indeed, menus, navigation, bonuses
and games can either be done in a
simple format, similar to DVD menus,
or with a Java runtime called BD-J.
As usual, there are no public
specifications, and even if there were,
a lot of the discs don’t really follow it,
so that requires a lot of work.
“DRM is of course the second big
mess. Blu-ray has multiple layers of
DRM. The two that are of interest to us
are AACS and BD+. AACS is a
documented crypto-system that relies
on cryptokeys and certificates. The
open-source community has a good
implementation of this, but without
the keys, it’s not really useful. And the
keys are per-media, per-software and
per-drive and they get revoked all
the time.
“To give you an idea, inserting a new
Blu-ray could revoke your drive
certificate and then you wouldn’t be
able to read any Blu-ray with this
device until you updated the firmware!
Even the ones that you already played!
So people share large configuration
files containing disk keys on various
websites... Not fun.
“The second DRM is BD+, which is
a full virtual machine that executes
the DRM code that could come with
the disk (we’re not joking). It’s very
hard to implement correctly, and
integrates also with the Java layers,
and has certificates too. There are no
good open-source implementations
of this system.”
So how does Joe Public fight back
against The Man, to rightfully play his
own discs? Well, the chief ways are
supplying keys and bug reports on
menus, with keys being the most
needed resource — although for legal
reasons, we cannot endorse this.
Being an experimental technology,
Blu-ray menus are disabled by default.
According to the Arch Linux wiki,
Blu-ray menus can be used if you
install ‘libbluray-git’ instead of
‘libbluray’, so you might need to do a
little digging if you’d like to get menus
working and contribute bug reports.
So what about keys? Well, that’s
where things get harder. If you have
AACS that FLA explained...
Subset/difference
tree system
Device key(s),
Sequency key(s)
Media key block (MKB)
Processing key, km
Recorded media with AACS
Volume unique key,
Kvu
AES-G
Volume ID
a Windows system about, then you’re
well catered for: just follow the link to
where you can upload keys and read
the info on what software to use, and
how to use it. Linux on the other hand
is a great deal harder: MakeMKV no
longer works the way the given how-tos
rely upon — they reference files and
folders that don’t seem to be there any
more — and further software and
documentation is buried away in an
endless maze of forum posts.
Despite spending several weeks
chasing down leads and trying
different methods, we just couldn’t
get our software to squeeze out a key.
And although we’d like to provide you
with a simple guide on key grabbing,
we’d probably find ourselves in
considerable hot water — so if you’ll
forgive us, we’ll remain deliberately
vague here. Either way, follow the links
and forum instructions, and hopefully
you’ll fare better than we did.
WHAT’S NEXT?
Perhaps you’re depressed by this state
of affairs, but seven out of ten discs
(at least in our quick test) isn’t too bad
a hit rate, is it? Plus, running without
menus by default is actually kind of
refreshing: instead of wading through
endless menus and warning screens,
you’re in the movie in a matter of
seconds. Looking at where Linux
Blu-ray was a few years ago, we can
confirm that development has come
a long way, and will only continue in
leaps and bounds if we can really get
behind it as a community.
Keys and menu testing aside,
what we really need to provide as a
community is boring old leg-work
DECRYPTION
Blu-ray contents are protected with a nightmarish
DRM system that makes DVD encryption look like
Ceasar cypher in comparison.
Encrypted title key(s)
Title key, Kt
CONTENT
Encrypted content
DECRYPTION
and organisation. We’re not trying
to be rude towards the developers,
but these last few weeks have been an
endless maze of old and broken links,
outdated documentation, and broken
bootstrap files. It’s understandable.
These people aren’t being paid for this,
and maintenance is the tedious
aspect of any software project.
Most programmers just want to get
on with the coding. If you would like to
contribute somehow but can’t program
yourself, perhaps you can help out in
these tedious admin jobs, and provide
updated how tos so that the coders can
spend more time on real tasks?
For any angry film executives who
might be reading, most of us probably
aren’t even interested in ripping, and
just want to rightfully play the discs
we’ve bought without having to change
OS. As far as we know, there are no
commercially available Blu-ray players
for Linux, and even though we are
open-source advocates, we’d still be
interested in a shrewdly-priced
proprietary program if given no
alternative — unless you can tell us
better.
So where do we sit in terms of project
completion and Blu-ray perfection?
We’ll give Jean-Baptiste the final word
on that: “For code, it’s mostly done.
For keys, it will be a long and neverending
battle.”
For more pointers on Blu-ray
playback than you’ll know what to do
with, see the excellent Arch Linux
Wiki: https://wiki.archlinux.org/index.
php/Blu-ray
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