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Know It All: DVD Encryption -- Broken DVD secrets

Published in Geare magazine, Issue #26, 2004

Some Hollywood movie-makers were a bit slow to latch onto the DVD. Companies like Warner Bros (which had co-developed the DVD) and Columbia TriStar were releasing movies on DVD as far back as 1997. But others were worried about pure digital copying of their movies. Their doubts were calmed by the development of CSS -- the Content Scrambling System -- which was thought to make it impossible to copy DVDs. Their movies came out. And now, it seems, it is apparent that CSS is next to useless. If you have a Windows computer with a DVD burner installed, you can copy commercial DVDs, with their full digital quality intact, for just the cost of a blank recordable disc.*

Of course, copy protection has existed for years. VHS cassettes have long been 'Macrovision' protected, which means that they send some data on the VCR's analogue video line that other VCRs or DVD recorders recognise. These recorders then do a lousy recording job (VCRs), or just won't record at all (DVD recorders). But analogue copying of video is not a huge problem anyway, especially with VCRs. The quality drops to appalling levels in no time at all.

But if a DVD could be copied digitally, then it could be copied perfectly. It was this that CSS was supposed to stop. The system was straight forward. The digital version of the movie is encrypted before being placed on the disc. The decryption key is right there on the DVD as well. But this is protected by an authentication mechanism, which involves a list of 400 additional keys. Each maker of a DVD player, whether a consumer model or software for a computer, has to pay a license fee in order to 'buy' one of these 400 keys. So, in theory, not only can't a DVD be digitally copied, it can't be played on an unlicensed DVD player.

Within the world of computer enthusiasts are those who think Windows stinks, and far prefer to use the Linux operating system. Some of these, operating in far-off Norway, were miffed that there was no software DVD player available for Linux, so they set about making their own. The end result was a computer program called 'DeCSS'. Get it? This initially used one of those 400 license keys which the programmers had extracted from a software DVD player.

They got their Linux DVD player, and Xing -- the software company from whose player the key had been extracted -- lost its license. From that time commercial DVDs have had a list of 399 manufacturer keys, and those discs won't play on the Xing DVD player. In late 1999 a 16 year old Norwegian lad was prosecuted for breaking the encyption system and making the program available. It wasn't until early this year [2004] that Jon Johansen finally emerged victorious from the legal actions launched by the Norwegian government.

In the meantime DeCSS was improved so it didn't rely just on the defunct Xing key. Knowing one key made it easy to find the other ones. The Motion Picture Association of America launched actions to stop various Web sites from carrying DeCSS, or even linking to it. But it turned out that DeCSS was a small program, and made even smaller as a hobby by anarchistic programmers, to the point where the whole program consisted of just seven programming lines in the PERL language! T-Shirts were produced, and coffee mugs as well, with the program printed on them. Any chance of keeping DVDs secure was long-gone.

Today you can download free programs for copying DVDs. Two of the best are 'DVD Decrypter' and 'DVD Shrink'. Just Google those terms and you'll find them easily enough. Commercial programs like 'Any DVD' decrypt DVDs in the background, making them work with regular copying programs. (For reasons of wishing to stay out of gaol, the company which created Any DVD, SlySoft Inc, is based Antigua!)

The major problem with copying DVDs, then, has been that until now recordable DVDs have been limited to 4.7 gigabytes in capacity. Most commercial DVDs require more capacity. Programs such as DVD Shrink allow you to choose just those parts of the DVD you want to copy, leaving out the Russian sound tracks and the special extras, to better fit a movie onto the recordable disc. It can even re-encode the movie using a higher compression ratio, although this involves some loss of quality.

But now dual layer recordable DVDs and burners are appearing. With their 8.5GB capacity, all bets are off. Full copies of DVDs, special extras and all, are now available to anyone for just the cost of a blank recordable DVD.

* Not that I would encourage such behaviour!

© 2002-2009, Stephen Dawson