March 5, 2008 3:04 PM PST

Blu-ray encryption scheme revolves around half life of films

Posted by Michael Kanellos

Call it the Harold and Kumar effect.

Now that Blu-ray has won the format war, the public and security industry will get a chance to see how well the novel encryption scheme that Blu-ray publishers and manufacturers works.

What makes the strategy somewhat novel is that is relies as much on consumer tastes and behavior as it does on technology, according to Paul Kocher, president and chief scientist of Cryptography Research, which helped devise the strategy.

Since some of you might now be gearing up to buy a Blu-ray player, here's how it works. Studios will hire software developers to encrypt their latest releases. Someday, hackers will find a flaw, crack the encryption and post the movie on the Internet. Once the movie is out in the wild "there is no way to make it unplayable," Kocher said. "You can't put the genie back in the bottle."

The studios, however, are banking on the idea that it might take months to crack a particular encryption scheme. By that time, the studios will have hoped that they have already pulled in the bulk of the revenue from that movie or title.

"Their business model is to make money in the first few weeks of release," he said.

That doesn't work with "Lawrence of Arabia." Film fans will likely be renting or buying that for years, so the studios will lose money on future sales.

But "Harold and Kumar Escape from Guantanamo Bay" or "Predator versus Alien versus Martin Lawrence as Big Momma"? How many people will be renting those movies three months after the initial release date on Blu-ray? I mean, other than film students writing a thesis? It's not like were talking about "Die Hard with a Vengeance" here.

Think of it. Go to your local video store and look in the section where they keep the movies from the 80s. When was the last time you had a burning desire to see "Ladyhawke?" It's like visiting a refugee camp.

Once a given encryption scheme is cracked, the studios then can shift to a new encryption scheme to start the cycle all over again. Hackers could try to break Blu-ray by creating a virtual copy of the hardware and thus fool the encryption on the disks, but that will be tough. "A Blu-ray player is a complicated piece of hardware," he said.

DVD encryption worked by targeting DVD players. The onus of encryption was largely on the device makers, which didn't have much economic incentive to improve it either.