New Blu-ray Discs to Expand Copy Protection, Bypass AACS Troubles

With a minimum of fanfare, the licensing body for the developers of a supplemental copy protection technology exclusively for Blu-ray Disc announced its initial specification for BD+ - which supporters had hoped would be available early last year - is finally ready for licensing to developers. 20th Century-Fox appears to be the first to board the bandwagon, having obtained a license for its developers to write for a virtual machine that will be embedded in future BD-ROM player devices.

One of the original sticking points between studios and technologists over high-definition disc formats concerned a provision of Advanced Access Copy System (AACS) copy protection that enables content providers to revoke a player's ability to decrypt new discs' content if the integrity of that content is found to be compromised for that player - in other words, if someone has hacked into the access keys and has posted them online, enabling others to copy the content.

While most everyone involved in the original high-def negotiations agreed that AACS' concepts of the "clearing house" for online activation of content and its media key distribution structure were necessary, its revocation ability was a key bone of contention. So the group that would eventually form the Blu-ray Disc Association presented a three-part alternative to AACS copy protection alone - the scheme backed by the DVD Forum, which supports HD DVD.

This scheme would buffer AACS by adding BD-ROM Mark technology, which stores access keys using a secret physical location scheme rather than within a logical file (that technology is already ready to go), and something called BD+. Once studied as an alternative to AACS altogether, BD+ relies on an embedded, programmable virtual machine that gives studios the option of creating title-specific security functions - mechanisms specific maybe even to just one movie.

Because BD+ could have been an alternative to AACS, studios and technology companies including Hewlett-Packard were told that it could override certain unwanted provisions. For example, it could enable a BD-ROM player whose rights were officially and technically revoked through the AACS system, to play a specific movie anyway.

It's part of what Blu-ray proponents call renewability, and they describe it in either of two ways: One way enables a movie disc whose PC-based media player or whose playback console has been compromised, perhaps maliciously, to deploy code that will actually patch the media player, undoing a hack.

The second way involves what HP described last year as a "repair sequence" that could not only undo the revocation of privileges for one movie, but perhaps repair a revoked player with patches that enable it to qualify for re-emergence into the community of accepted BD decoders.

Whether that feature remains in the final specification, however, may have been thrown in doubt by this statement from a technology licensing firm that contributes to Blu-ray: "BD+ Content Code is 'non-persistent,' meaning it secures only the playback of the content contained on its disc and is deleted when the disc is ejected. The player is then returned to the state it was in prior to the disc being inserted."

The ability for a player to crawl back from revocation might have been a feature that would have tipped the scales in Blu-ray's favor in 2006. BD+ was obviously delayed by an extraordinary length of time, but then again, so was AACS' own revocation ability anyway, so the damage to Blu-ray's reputation may not be that great. Advocates and supporters of the format have admitted holding off on excessive initial purchases of Blu-ray content, knowing that more capable BD+ endowed versions would eventually be in the works.

But the Web site of BD+'s official licensing arm isn't saying much about what was and what was not retained in the final specification - its FAQ page is actually empty, leading to an even more frequently asked question, "Is this format actually ready?"

Blockbuster's decision Monday to expand its selections in many of its retail outlets to feature Blu-ray titles and not HD DVD may have given Blu-ray the edge, at least for now, in its standing among consumers. BD+ could potentially give Blu-ray a similar edge over HD DVD technologically, if its supporting studios and manufacturers play their hand properly. On the other hand, BD+'s unique copy protection capability could make Blu-ray a unique target for engineers seeking to crack its codes; and if they succeed, HD DVD advocates may be waiting with thumbs in their ears and tongues extended.