UNINNOVATE / Engineering At Its Finest

HD DVD is one of two leading high-definition video disc formats attempting to replace DVDs. An HD DVD disc can store about four times as much data as a DVD disc and it supports playback of “true” high-definition video. In addition, HD DVDs have more advanced copy protection than DVDs. The movie industry has been trying to shift the market away from DVD and towards high-definition formats partly because DVDs have become so easy to copy.

Both HD DVD and it’s main competitor Blu-ray were finally released this year after long delays caused by disagreements over what kind of copy protection the discs should carry. In fact, the DVD Forum announed that HD DVD was the official replacement format for DVD all the way back in 2003. Many have cited the long delay to market as part of the reason HD DVD and Blu-ray have so far failed to capture public interest the same way that DVD discs did when they were first released.

It seems fitting then that the copy protection that for so long delayed the release of HD DVD has already been at least partially cracked. And the author of the crack claims to have been encouraged to do it because of the strict playback limitations built into to format which were meant to prevent piracy:

“I just bought a HD-DVD drive to plug on my PC, and a HD movie, cool! But when I realized the 2 software players on windows don’t allowed me to play the movie at all, because my video card is not HDCP compliant and because I have a HD monitor plugged with DVI interface, I started to get mad… This is not what we can call “fair use”! So I decide to decrypt that movie. I start reading the AACS specification I have found on the net. I estimate it will take me about 4 weeks of full time job to decrypt that. I was wrong, it was in fact, easy…”

Forum post by muslix64, author of BackupHDDVD

However, things are not quite as simple this time around as they were with DVDs. Time for a little background information:

There are at least three parts to every movie encryption scheme - the encrypted movie which can’t be played, the secret key that lets you decrypt the movie, and finally the original unencrypted movie that can be watched. The idea is that a consumer buys an encrypted movie on a disc and an approved player. The player contains the secret key that turns the movie back into it’s original form. Without a player with the secret key, the movie can’t be watched and is just a useless disc of plastic.

The problem is that since the consumer physically controls the player, the consumer is free to disassemble it. If the consumer is smart enough, he or she can eventually pull the secret key out of the player and then use it to watch any copy of any movie without restrictions. That’s how DVDs were originally broken - a teenager figured out how to get the secret key out of the Xing DVD playback software (and more flaws were discovered later that made DVDs even less secure).

However unlike DVDs, the HD DVD copy protection scheme supports “revoke-able playback keys”. If one HD DVD player key is recovered, any new HD DVD discs will be specifically encoded to no longer work with that compromised player. So even if the current HD DVD format is cracked, new discs produced later will still be protected - at least that is the theory.

So at this point it is unknown how long this crack will prove to be effective. But one thing has been clearly demonstrated - all of the time and energy spent uninnovating the HD DVD format has resulted in a slower time to market and considerable anger from the most knowledgeable group of consumers - the ones capable of breaking the protection formats.