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Breaking News: BD+ Broken

November 2nd, 2008 1 comment

BD+ is the DRM system for Blu-ray discs, as Wikipedia puts it:

BD+ is a component of the Blu-ray Disc Digital Rights Management system. It was developed by Cryptography Research Inc. and is based on their Self-Protecting Digital Content concept. BD+ played an important role in the past format war of Blu-ray Disc and HD DVD. Several studios have cited Blu-ray Disc’s adoption of the BD+ anti-copying system as the reason they supported Blu-ray Disc over HD DVD.

One of the more humorous observations was that unlike DVD (which used DeCSS for its copy protection system) and AACS which powered the bulk of the HD-DVDs of the time that BD+ would uphold its protection for atleast the next 10 years. This may have been one of the key factors in the HD-Wars, but alas it seems someone  has found a way of traveling into the future and finding the break.

Oopho2ei (who claims is not a professional programmer :O) from the Doom9 forums along with a few others (bmnot, schluppo, Disabled, evdberg) have (it seems) successfully broken the BD+ protection scheme in a grand total of 5 weeks and 3 days (started on the 24th of August). They have restored the BD+ protected “The Day After Tomorrow”:

I am glad to announce the first successful restoration of the BD+ protected movie “The Day After Tomorrow” in linux. It was done using a blue ray drive with patched firmware (to get the volume id), DumpHD to decrypt the contents according to the AACS specification and the BDVM debugger from this thread to generate the conversion table. The conversion table is the key information to successfully repair all the broken parts in m2ts files to restore the original video content. This small tool was finally used to repair the main movie file “00001.m2ts” according to the conversion table.

To verify the correctness i compared my 00001.m2ts with the one AnyDVD-HD creates and they both match. The MD5 hash of this 30GB large file is in both cases “0fa2bc65c25d7087a198a61c693a0a72”.

Breaking the code is no simple feat, Oopho2ei and team has had to reimplement the VM that runs the BD+ protection layer and realises that there’s a fair chance that it could be blocked at a later stage and may phone-home:

There has to be some kind of firewall around the virtual machine which validates all communication between the ( potentially hostile ) content code and the outside world (traps and events). Part of the rules which are enforced by that firewall are the parameter checks on every trap call. It’s obvious that the traps and the event handling itself has to be carefully implemented. I believe this additional effort is necessary to prevent the content code from breaking out of it’s sandboxed environment and do nasty things like gathering user information and “calling home” when it detects an unlicensed emulator. So because these additional security measures make things more difficult i suggested to test this code first with the easy traps.

Even a guy from SlySoft (who makes the ever popular AnyDVD-HD product) chimes in early on but backs off after realising he could well get the sacker.

I’ll just say: due to certain properties of BD+, once you’re past a certain point, you can handle it pretty much without reversing – BD+ itself then helps you out – on any player

Actually you’d have to know how BD+ really works, to know what I meant (and even then you probably wouldn’t ).
But if I start unraveling that, I’d be finding myself looking for a new job by next week

Love this bit in one of Oopho2ei posts:

I would like to stress again that this project wasn’t intended to circumvent copy protection and promote piracy. This can already be done using commercial software like AnyDVD-HD. Instead this project was an attempt to enable users of open source operating systems (like linux) to playback their BD+ protected discs without having to use proprietary software. Furthermore only two movies “I Robot” and “The Day After Tomorrow” have been proven to be handled correctly so far. Obviously there is still a lot of debugging to be done.

Classy! Download a copy of the BDVmDbg build for educational reasons and try PortableBDVM which comes in C99 source form.

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