Welcome to Doom9's Forum, THE in-place to be for everyone interested in DVD conversion. Before you start posting please read the forum rules. By posting to this forum you agree to abide by the rules. |
5th February 2007, 22:43 | #21 | Link | |
Registered Developer
Join Date: Sep 2006
Posts: 9,140
|
Quote:
|
|
5th February 2007, 22:54 | #22 | Link | |
Registered User
Join Date: Sep 2006
Posts: 390
|
Quote:
Why is it not entirely accurate? Well to let a known plaintext work it doesn't have to involve just one encryption step (you do not have to know the Media Key in advance). Lets say we have a disc containing a MKB. In that MKB is a verify media key record. In essense this means: if you think you have found the media key using one of many possible Device Keys (which you try one by one using the memory dump as seed) then you can check if its valid. So yes you can go for Device Keys directly. But its a lot harder I think (because of the way the subset difference algo works). The future will tell whether its easier to go for Device Keys (and then for Media Keys) or for Media Keys directly. Ok. Lets go for this Media Key shall we? And more Volume IDs are helpful too . Regards, arnezami PS. And I'm not talking about variant keys. Those a (little) harder still... Last edited by arnezami; 6th February 2007 at 08:16. |
|
5th February 2007, 23:06 | #24 | Link |
Registered User
Join Date: Sep 2006
Posts: 390
|
I was mostly referring to Volume and Media Variant Keys which you definitely need to decrypt all the content (otherwise you would miss like 1% or something and the video would basicly be broken at certain parts). This is the nastiest part of AACS in my opinion and I wonder when (and if) they will use it. Hopefully later than sooner.
|
5th February 2007, 23:21 | #25 | Link | |
Registered User
Join Date: Dec 2006
Posts: 154
|
Quote:
|
|
5th February 2007, 23:51 | #27 | Link | |
Registered User
Join Date: Sep 2006
Posts: 390
|
Quote:
But the idea that one difficult to obtain key (in this case a Device/Process Key) would make it possible to decrypt discs using easier to obtain Volume IDs (or even guessable/computable). Therefore making a fairly independent decrypter (not needing too much updates) possible. |
|
6th February 2007, 00:26 | #29 | Link | ||
Registered User
Join Date: Sep 2006
Posts: 390
|
Quote:
Anyway. Here is the quote from AACS common specs dealing with Processing Keys: Quote:
Anyway. I think we should start thinking about what happens in a few months or so. They will probably revoke the current version of WinDVD and possibly other software players (just to be safe). The questions is: How are non technical people without too much hacking/programming experience (but with lots of new movies) gonna retrieve keys? I believe a higher order key (Processing/Subsidiary Device Key/Media Key) could be very helpful for them to extract volume keys (assuming the simple mem search used right now with WinDVD won't work anymore for them). I think we are not disagreeing on that part. And I agree its very easy now (even without higher order keys) because of WinDVD. But thats the only thing now that allows many people to get VUKs. But thats not gonna last. I guess the thought behind all this is: lets prepare for what will happens next. Let me be straight: I don't want to replace something that is clearly working (extracting VUKs) but I want to add something in the context of probable future events. Regards, arnezami Last edited by arnezami; 6th February 2007 at 08:19. |
||
6th February 2007, 07:40 | #30 | Link |
Registered User
Join Date: Sep 2006
Posts: 390
|
Concerning the differences in the MKBROM.AACS files. I am wondering which parts of the MKBROM.AACS file differ from movie to movie (or from disc to disc?).
The most important part (for us here) is the Verify Media Key Record. In my MKBROM.AACS its at position 74h (just before the Copyright text): Code:
00000070: xx xx xx xx 81 00 00 14 87 B8 A2 B7 C1 0B 9F AD 00000080: F8 C4 36 1E 23 86 59 E5 xx xx xx xx xx xx xx xx I am now very curious if this part if different for other movies. Or if some movies have the same one. So if somebody could check. That would be great . arnezami PS. The start of the MKBROM file is probably the same for everyone: 10 00 00 0C 00 04 10 03 00 00 00 01. The last four bytes represent the version number. Last edited by arnezami; 6th February 2007 at 08:14. |
6th February 2007, 08:33 | #31 | Link |
Dwight Schrute's homeboy
Join Date: Jan 2007
Location: The Office
Posts: 136
|
Is this the right area?
Code:
00 00 00 00 00 00 00 00 00 22 00 00 40 00 04 06 32 04 20 11 57 47 48 44 56 4D 00 00 xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx Last edited by jokin; 6th February 2007 at 13:04. |
6th February 2007, 10:07 | #32 | Link |
Registered User
Join Date: Sep 2006
Posts: 390
|
Code:
Lentgh Code: 00 22 00 00 Volume ID: 40 00 04 06 32 04 20 11 57 47 48 44 56 4D 00 00 MAC: xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx I still see structure. Maybe we can figure out what it stands for (like the date/time thing in my example). arnezami PS. Its best to remove the MAC bytes like I just did for your own protection. Last edited by arnezami; 6th February 2007 at 22:30. |
6th February 2007, 10:53 | #34 | Link | |
Registered Developer
Join Date: Sep 2006
Posts: 9,140
|
Quote:
In other words posting a processing key on the internet allows many people to decrypt their HD DVD discs without having to search for VUKs first. At the same time the device key is still secret and so cannot be revoked. Did I get this right? |
|
6th February 2007, 12:03 | #35 | Link | |
Registered User
Join Date: Sep 2006
Posts: 390
|
Quote:
When I've got more time I may be able to explain this better. Personally I believe its much more likely we will only find one Device Key (while we should release a sub device key or processing key) when hacking a software player. But I can only explain that while also explaining the full subset difference algo. arnezami |
|
6th February 2007, 12:06 | #36 | Link |
Registered User
Join Date: Dec 2006
Posts: 202
|
Yes, you got it right, although "discs" should be "disc" (single). The processing key will just like the VUK be different for every disks ... and the way you have to search for the processing key is the same as for the VUK, so why bother ?
|
6th February 2007, 12:16 | #37 | Link | |
Registered User
Join Date: Sep 2006
Posts: 390
|
Quote:
But what I'm really interested in the the difference you mentioned between the MKBs. Are the versions different? Are the Verify Media Key Records different? Or is it for example the Copyright text (eg 2006 changed into 2007) which causes the signature to be completely different and it may therefore look like a quite different MKB (while the Media is still the same). I just don't know. I only have one disc. Please help us out here . arnezami Last edited by arnezami; 6th February 2007 at 12:25. |
|
|
|