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Content Protection for High-Def DVD  (4/2006)

    by Douglas Dixon

Content Protection Mechanisms

(See High-Def DVD: Blu-ray and HD DVD)

The new high-def DVD formats are coming -- Blu-ray Disc ( and HD DVD ( formats -- the products are almost ready, but it's up to the market to decide this race, driven by the availability of content.


Earlier this year there were further delays in getting to market, attributed to the negotiations over the AACS (Advanced Access Content System, copy protection mechanisms. In addition, Sony announced more bad news for its bottom line, with the related delay in getting its new next-generation PlayStation 3 video game system to market.


Content Protection Mechanisms

The IRMA Recording Media Forum in March 2006 (, Brad Hunt, executive vice president and chief technology officer for the Motion Picture Association of America (MPAA, , provided an extensive and eye-opening survey of the range of digital content protection and rights management technologies being deployed with these new formats.

Besides the base encryption and unlocking technology, these high-def DVD formats also include:

- Two mechanisms that can disable playback of working players and discs if they have been deemed to be hacked (Media Key Block and Content Revocation List), triggered by updates to lists of revoked equipment distributed with new content. Any new disc could cause your existing personal property to stop working.

- A renewal requirement that can disable working discs and players (for both hardware devices and software players) if they are not "renewed" after a period of time -- assuming the original vendor is still in business and offering the service -- or required upgrade

- A playback control audio watermark technology (Verance) which can shut down playback of consumer recordings if the system decides they originated from a protected source. Just try to view your personal videotape of your daughter's birthday party if a protected movie happened to be playing in the background.

- Two optional flags that constrain analog output -- the ICT (Image Constraint Token) to limit image resolution, and the Digital Output Only Token to totally disable all analog video output. Early adaptors will need to replace their expensive home theatre systems if they lack the now-required HDMI connector.

- Three approved mechanisms for protecting digital content as it is transmitted to a display or over a network -- DTCP (Digital Transmission Content Protection), HDCP (High-bandwidth Digital Content Protection), and WM DRM-ND (Windows Media Digital Rights Management for Networked Devices). Your working PC or TV display can go black if there is a glitch in the hardware interconnect.

- Two sunset provisions to remove HD analog video output (Dec. 2011) and even all analog output (Dec. 2013) from all future products. You will not be permitted to watch your content as you currently watch DVDs, even downsampled on analog standard-definition sets.

... And these are only the initial requirements of the AACS Interim Adopter License, released in February 2006 in order to allow initial products to ship. Additional requirements will be imposed in the final license, for Managed Copying, Digital Output Only Token, and Audio Watermark detection.

And there's more, as Blu-ray products include additional BD+ and BD-ROM mechanisms that can prohibit playback if a disc is deemed improperly marked, or hacked.


Yikes! Especially if you are a technologist, like me, you can't help being concerned about the implementation all these layers of complexity, and have misgivings about all the ways that widespread deployment of brand new technology to the mass consumer market could blow up in our faces (think of Sony's recent adventure with CD copy protection).

We've already seen this kind of thing happen with the CPRM / VCPS copy protection for recordable DVDs that is being built in to consumer DVD recorders without any notice or explanation to consumers -- A recorder can decide to silently and invisibly mark a consumer recording, and players (and even a software players) can decide that your content is protected, and inexplicably refuse to play personal recordings.

One mistake in the implementation of one of these technologies in a popular release, one time bomb in a common hardware chip, one low-cost product rushed to market, maybe even a hack delivered over the broadband connection, and the industry will have a major problem as millions of discs and players stop working with no apparent cause or explanation for consumers.

Just this year, the industry has taught consumers to fear physical CD media bearing rootkit hacks, and now they are going to be told that their legally-purchased high-def media and players can stop working at any time, especially if they try to play new legally-purchased media. The lesson that's being sent is that more and more, downloaded content off the Internet just looks like the safer alternative.



Blu-ray Disc (BD)

AACS (Advanced Access Content System)