cache css keys for use with dvd images

Discussion in 'AnyDVD HD (DVD issues)' started by thetoad, Nov 21, 2020.

  1. thetoad

    thetoad Well-Known Member

    So, this isn't such a practical issue for me these days, but figure I'd throw out a feature idea that might improve anydvd a bit for DVDs.

    It's well known that DVDs and BluRays get scratched. this sucks, and can make ripping difficult. My workflow for these discs was to just contentiously run ddrescue over them (in the past had shared some of my logs with you for MoD bluray discs with bad blocks), until I got a complete image. The image is encrypted, so can't be used as is.

    for BluRays, this wasn't a problem, either AnyDVD already knew the VUK or I could stick the physical (difficult to read disc) into the drive and AnyDVD would calculate the VUK. It could then use any mounting program to mount my fully read encrypted image and decrypt it.

    I don't believe a similar thing can be done for DVDs (i.e. cache the calculated key and use it later). In fact, if memory serves me (and I think I might have talked about this small point before), AnyDVD wont even try to brute force the keys off a mounted encrypted image, the mounting program says its not encrypted, so it just assumes its not (as opposed to BluRays where the AACS directory shows that its encrypted).

    what I used for my workflow was old school dvd decrypter which can brute force (generally, not always) the keys off a mounted encrypted dvd iso (do iso to iso to avoid other protection schemes).

    However, as I said "generally", as small VOBs (I believe) can't be brute forced, need a certain amount of data. Now, generally, those small VOBs dont matter that much, but it still be better to be perfect, hence the idea that it be nice if AnyDVD could calculate and cache the keys from a physical disc (like it does for BluRays) and use them to fully decrypt the disc.

    just a thought.
  2. James

    James Redfox Development Team Staff Member

    I am lost. AnyDVD already caches CSS keys..??
  3. thetoad

    thetoad Well-Known Member

    but it doesn't use them for iso images with css encryption still on them. I believe we've talked about that before, I'm motivating why it would be valuable to ignore what the virtual drive says (no css) and act like dvd decrypter if the individual blocks have the css bit set. Or at least have an option to ignore what the drive says and use the cached css keys.

    i.e. there are times where one needs to create an iso with encryption as that's the only effective way (as many many many many rereads with ddrescue + many many cleaning attempts in between) to get a complete disk image. AFAIK, anydvd doesn't provide any way to decrypt said image, that's what Im trying to motivate. While I was able to read them with dvd decrypter, as noted, that only works for VOBs that can be brute forced, I think AnyDVD can do better, as you says, it caches the keys.

    now, perhaps its "impossible" (or at least would need a new fingerprinting algorithm) to connect those css keys to a dvd image (as opposed to blurays) as the drive is part of the fingerprinting process, but I still think it be of value.

    but as I said, less value to me these days as I've exhausted my formerly huge supply of DVDs, but figure it could be useful to others.

    is that clearer?
  4. James

    James Redfox Development Team Staff Member

    Yes, thank you.
  5. thetoad

    thetoad Well-Known Member

    so any chance it would be considered? i.e. do you guys find the use case I describe valuable?
  6. James

    James Redfox Development Team Staff Member

    No, sorry.
  7. thetoad

    thetoad Well-Known Member

    oh well.