Device key revokation

Discussion in 'AnyDVD HD (Blu-ray issues)' started by David Anderson, Feb 13, 2007.

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  1. Previous posts by SlySoft members seem to indicate AnyDVD-HD can decrypt all HD-DVDs, not just the ones in which the title or volume keys are already known (the BackupHDDVD approach).

    If the title key is not already known, then there is only one other way to decrypt the content; a device key must be used to decrypt the title key. Once you have the title key, you can decrypt the content.

    CSS decrypters (AnyDVD, DVD Decrypter, DVD43, etc) use one of two methods to decrypt: either a brute force attack on the key (not too hard when the key is only 40 bits) or cycle through a list of known compromised device keys.

    To decrypt AACS, a brute force attack is not feasible due to the size of the key (128 bits). That leaves only one option - a device key must be obtained from either a compromised software DVD player or hardware DVD. Given the difficulty in reverse engineering hardware and the limited amount of time hardware DVD players have been available, it's a safe bet to assume AnyDVD-HD uses a device key obtained from a compromised software DVD player.

    One of the key security features of HD-DVD is the ability to revoke device keys. One can assume that if and when the device key used by AnyDVD-HD is revoked, it will no longer be able to decrypt new DVD releases. Unless SlySoft has an unlimited source of compromised device keys, I fail to see how this product will remain viable once the device key used by AnyDVD-HD has been revoked.

    HD-DVD was designed to stop this well known technique of using device keys, as it’s the basis for present day CSS decrypters. I’m assuming SlySoft knows all about device key revocation, yet they are still willing to release AnyDVD-HD. What I’d like to know is if I purchase AnyDVD-HD when it's released, will SlySoft reimburse me if the device key is revoked a few days or weeks later, rendering the product useless for all future DVD releases?

  2. Peer

    Peer Redfox Development Team Staff Member

    Hi David,

    beforehand I'd like to point out that at present, I cannot give you any details about exactly how AnyDVD HD works - you can probably imagine, that this would be a very stupid thing to make public for several reasons.

    All I can say, is that AnyDVD HD uses several different mechanisms and that the simple revocation of a device key will not render it useless at all.

    About brute forcing 40bit keys: nope, if that really was neccessary to decrypt the good old DVDs, it wouldn't work too well. Brute-forcing 40 bits - even with today's hardware - takes a considerable amount of time, at least longer than you would be willing to wait for the damn DVD to play :)
    The reason that CSS keys can be brute forced, is mainly because of a design flaw in the encryption protocol (and yes, sure, the weak key-length does help alot as well).

    About refunding: any version of "classic" AnyDVD works with all DVDs known up to that date. New copy protections have to be "undone" pretty much every week, by adding code to AnyDVD.
    Theoretically, there could come the day, when Slysoft doesn't manage to break a new DVD-copyprotection (highly improbable though).
    Now, with HD-DVD nothing much has changed.
    It still is possible, that AnyDVD HD will no longer work with all new HD-DVDs starting from day X and we won't find a cure - for no other reason than this is the case with AnyDVD "classic".
    If we can't, we simply just can't. But it will definitely keep working with all HD-DVDs up to that date.

    Having quite deep insight into AACS as the job requires it, I can tell you, that AACS even has a few more flaws than CSS ;)

    So stop worrying, this is a topic that should bring joy and happiness to you! :D
    Last edited: Feb 13, 2007
  3. simple

    simple Active Member

    and this is why anydvd and the slysoft team remain the number one choice:bowdown: :bowdown: :bowdown: brown nosing points accepted...LMAO:p
    Last edited: Feb 13, 2007
  4. Thank you for your response. My question wasn't about future authoring techniques (a.k.a. "protections" like Arccos and RipGuard). Certainly nobody knows what the future holds for HD-DVD in this respect. One can't expect a program to work flawlessly on new authoring techniques which have yet to be revealed.

    I was referring to the encryption on HD-DVD, something that will not change on future DVDs - it's essentially frozen for the life of the format. I'm worried about the weakness of using a device key to obtain the title key, which can be easily revoked.

    Unless you have uncovered a major blunder on the part of the HD-DVD consortium when it designed the current protection scheme, I still feel the revocation of the device key would be a major problem.

    I'm not looking for a guarantee that AnyDVD-HD will remove or eliminate future protection schemes, no software could make that claim.

    I am looking for a guarantee AnyDVD-HD will simply decrypt all HD-DVDs, past, present and future. This is something that you can put in writing if you are not using a device key. Any design flaw you have uncovered in the encryption algorithm used on HD-DVD will appear on all HD-DVDs, past, present and future. Therefore, you should be able to guarantee AnyDVD will decrypt all HD-DVDs, unless you are using a device key which has been revoked.

    I dislike being the devils advocate, but someone has to ask the question.

    David :)
  5. Raptus

    Raptus Member

    Hello David,

    decryption or revokation won't be a problem anymore, now that the (one) Processing Key was found. See:
    This key is enough to decrypt all HD-DVDs and BluRays and I'm sure that by now AnyDVD HD profits from that...
  6. jackyl

    jackyl Member

  7. Hi, If you read the whole thread, you'll discover that having the Processing Key is not the holy grail we are hoping for. Even with the Processsing Key, you must still obtain the Volume ID, and no one has automated that process yet. Also, just like device keys, Processing Keys can be revoked (changed) on future DVDs. They will also likely use better methods of hiding the Volume ID (encrypting them instead of leaving them in plain text), so there are many pieces to the puzzle yet unsolved.

    I haven't seen SlySoft deny they are using a device key yet, as this is the simplest approach for a universal solution... until it's revoked.

    I'm encouraged by Arnezami's work (, he's a really bright guy who given time may resolve some of these issues. Once he reveals all he knows, we can expect to see free decrypters popping up. If SlySoft uses this future knowledge (or anything they have uncovered on their own), they could conceivably have a good decrypting solution. Coupled with SlySoft's ability to foil most authoring techniques designed to prohibit copying, it could be a great product. I'm just skeptical at this point about the decrypting capability.

    David :)
    Last edited: Feb 14, 2007
  8. You can't assume that everything you read is accurate. In fact, this newsflash is missing important information, leading one to believe that all you need is the Processing Key to unlock every DVD. What's missing is the Volume ID. As I mentioned in a previous post, the Processing Key can be changed, as well as how the Volume ID's are utilized (ie. they can be encrypted in memory).

    David :)
    Last edited: Feb 14, 2007
  9. Peer

    Peer Redfox Development Team Staff Member

    No, now please, don't get too excited about that processing key - there is being much fuss made about it, I don't really understand why.
    AnyDVD HD is not using this key, BTW.

    The processing key still will not decrypt all HD-DVDs by itself. Another information is required: the Volume-ID.
    This still either has to be fetched out of the memory of some weakly programmed HDDVD-software or read directly from the drive. The drive will only reveal it with proper authentication - and for that you need a Player-Key (often confused with the device key, but they are two distinct secrets).

    Also: this processing key will most certainly only work with HD-DVDs mastered with an MKB version 1. As soon as any device gets revoked, the MKB version will change and a different processing key will be valid.

    The way I see it, the processing key didn't bring them much closer to their final goal. Previously, you had to fumble VUKs out of WinDVDs memory, now it's the Volume ID - admittedly, a little easier to identify, as it always starts with 0x40 00.
    When WinDVDs keys get revoked, you can bet on Intervideo not being so stupid to leave this hole open.

    Sad thing: we already had the whole AACS done, when the boys from doom9 were still gathering title-keys from WinDVDs memory - but they're getting all the press... :doh: (hey, no offence, guys, you're doing the right thing :))
  10. Peer

    Peer Redfox Development Team Staff Member

    Well - even a device key is not the universal solution. You will still require the Volume-ID :)
  11. Since you don't deny using a device key, it's safe to assume you do. That is of course worrysome for anyone who buys AnyDVD-HD.

    David :(
  12. Gothmoth

    Gothmoth New Member

    let me add a question...

    as far a i know Bluray and HD-DVD both use AACS.... correct?
    when it´s true that you are done with AACS......

    then why not supporting Bluray too?

    im curious why all the world is reporting about the complicated DOOM9 hacks and workarounds when slysoft claims to have a soft already that can copy
    every existing HD-DVD .
    do i miss something here.... ???
    Last edited: Feb 14, 2007
  13. Peer

    Peer Redfox Development Team Staff Member

    It's not about AACS - you're right, decrypting Bluray is not the hurdle.
    It's about file formats, that differ and need to be considered and some other small differences. Nothing, that really requires too much brainwork, but it's work anyway. So that is why we are currently concentrating on finishing HD-DVD first.
    Also, BD+ might give us some pain (don't know, if any discs with BD+ are out at all) - I know nothing about it yet, haven't bothered with Bluray much so far, to be honest...
    In one or two weeks we're going to start to take a closer look at it, I promise.

    Me too :)
  14. Webslinger

    Webslinger Retired Moderator

    Slysoft never stated that they were or that they weren't. So, it's not safe to assume anything. What Slysoft isn't going to do is give you explicit details about how its program works. If you don't want to buy Anydvd HD, that's your choice. I'm willing to bet many people do want to buy Anydvd HD.
    Last edited: Feb 14, 2007
  15. SamuriHL

    SamuriHL Well-Known Member

    Yea, seriously, let it go already. They're not going to give you the secrets to how it works. If you're so concerned about device keys, then don't purchase it. You keep saying the same thing over and over. They get your point already. They're simply not going to respond to it.
  16. Webslinger

    Webslinger Retired Moderator

    Hey guys, can you please tell me how Anydvd HD works so I can release a competing product? Actually, I'll tell you the truth: please let me know, so I can save time from reverse engineering Anydvd HD to ensure Anydvd HD no longer works on new HD-DVD releases. PM me the code please.

    Last edited: Feb 14, 2007
  17. SamuriHL

    SamuriHL Well-Known Member

    Pretty much. Sorry for my snippy response but good Lord, he just won't let it go already. He's so on about device keys and how Slysoft won't deny using them. Given my history with this company, I'd trust them every time. I've never once had a problem that they didn't fix. Given their history and how quickly they dealt with HD-DVD, I'm willing to give them the benefit of the doubt that if they encounter a problem, they'll fix it. And if they can't, they can't. You always take that chance. You have to decide whether it's a chance you're willing to take or not.
  18. Try to be respectful...

    I didn't realize this thread needed a moderator to set things straight. If you have any knowledge on the topic, I'd be glad to have your feedback.

    SlySoft has already made statements about what they are NOT doing to decrypt, for example:

    I only asked for confirmation they were NOT using device keys; surely asking someone what they are NOT doing will not divulge secrets.

    Using device keys is a much easier solution than any of the techniques being slapped around on the doom9 or elsewhere. The problem is, it’s also easy to black list a device and because AACS was designed with blacklisting in mind, it will not be a public relations nightmare to do so (contrary to what some have speculated), especially if the device keys come from a compromised hardware DVD player.

    You might want to read about the clever technique used to store such a large number of device keys in such a small header on the disc, using a technique called “Subset Difference” (more on that here: ). This allows a set of device keys for one player (just the one which was compromised, not all models produced by the manufacture) to be revoked. If SlySoft is using device keys, it’s unlikely they would have gotten them from a hardware player when it’s so much easier to extract them from a software player.

    As “Peer” (SlySoft) mentioned, knowing the device key alone does not allow one to decrypt an HD-DVD. The device key does however allow you to calculate the media key. Once you have the media key and the volume identifier, then you can decrypt the title key and ultimately the encrypted video. I’m assuming that creating an automated process to find the volume identifier has already been accomplished by SlySoft (otherwise they would not have a working product), so all I wanted to be sure of (and reassure those who spend money to buy the software) was that they were not using device keys to read the MKB, otherwise this could be easily revoked.

    I haven’t received a reply to my question, so I won’t ask again. I appreciate the feedback I received from SlySoft and I have great regard for their technical abilities. I’m sure in time AnyDVD-HD will be the ultimate HD-DVD decrypter.

    Last edited: Feb 14, 2007
  19. Charlie

    Charlie Well-Known Member

    This was on google news this morning and there is allot said on it but yet limited as well.

    Some of the comments. The publication of this latest key, called a processing key, gives users a much easier way to figure out the volume keys they need in order to make movie copies with the HDDVDBackup software, according to Arnezami.
  20. ChiefNuts

    ChiefNuts Member

    There is no reason to explain anything. The less the public knows about how AnyDVD 'classic' or HDDVD does it's magic is better for the public. because thoes AACS guys are part of the public, and if we can read it, they can read it. I'm just glad that I can backup and watch my HDDVD collection on a non-HDCP connection in all it's hd glory.

    Thank you.
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