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HD DVD requires Digital Imprimatur to authorise playback.

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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_
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