HD DVD requires Digital Imprimatur to authorise playback.

Discussion in 'DVD Video' started by Allan, Jul 25, 2005.

  1. Allan

    Allan Guest

    HD DVD requires Digital Imprimatur to authorise playback

    A while back there was a mention that the next generation DVD format,
    HD DVD will use the sophisticated content protection system AACS.
    According to the AACS Pre-recorded Video Book Specification, in order
    for media and players to be AACS compliant, a disc can only be
    published if it contains a digital imprimatur and players for the
    media must reject any work that lacks a digital imprimatur. An
    imprimatur is the latin for "let it be printed", which means that a
    work cannot be published without first being approved by some central

    Every disc that is published must contain an up-to-date list of
    revoked works and when ever a disc is loaded, the player must update
    its revocation list and prevent the playback of any disc that contains
    a revoked digital imprimatur.

    If the HD DVD format becomes the main format for movies, the AACS
    organisation will likely decide on who handles the digital
    imprimaturs. The AACS organisation is founded by several members from
    both the HD DVD and Blu-ray sides such as Sony, Toshiba, Microsoft,
    Disney, Intel and so on. Unfortunately, as there will likely only be
    one single central organisation reponsible for issuing digital
    imprimaturs, they may be subject to anticompetitive abuses as this
    organisation would be reponsible for the authorising of every single
    HD DVD disc for publishing.

    HD-DVD, one of the two candidates for the next-gen DVD format, uses a
    “content protection” technology called AACS. And AACS, it turns out,
    requires a digital imprimatur on any content before it can be

    (The imprimatur — the term is Latin for “let it be printed” — was an
    early technology of censorship. The original imprimatur was a stamp of
    approval granted by a Catholic bishop to certify that a work was free
    from doctrinal or moral error. In some times and places, it was
    illegal to print a work that didn’t have an imprimatur. Today, the
    term refers to any system in which a central entity must approve works
    before they can be published.)

    The technical details are in the AACS Pre-recorded Video Book
    Specification. The digital imprimatur is called a “content
    certificate” (see p. 5 for overview), and is created “at a secure
    facility operated by [the AACS organization]” (p. 8 ). It is forbidden
    to publish any work without an imprimatur, and player devices are
    forbidden to play any work that lacks an imprimatur.

    From what I can see, if a HD DVD player is forced to reject HD DVD
    media that lacks a digital imprimatur, this means that blank media
    must also contain a digital imprimatur in order for a HD DVD player to
    allow playback. This likely means that should someone succeed in
    copying HD DVD movies and illegally resells them, then it is possible
    revoke all (or at least the majority) of media that the pirate has
    used. If this is true, this is likely one method the movie industry
    will use to tackle piracy in the future.


    "Arguing with anonymous strangers on the Internet is a sucker's game
    because they almost always turn out to be -- or to be indistinguishable from
    -- self-righteous sixteen-year-olds possessing infinite amounts of free time."
    - Neil Stephenson, _Cryptonomicon_
    Allan, Jul 25, 2005
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