Buy a copy of the matrix on DVD and take it home. Play it on a Mac or on a Windows PC and you're in for a pretty good time. But play it on a PC running the Linux operating system, and the movie industry says that you're breaking the law.

Your transgression is that of "circumvention," a criminal act created by the 1998 Digital Millennium Copyright Act. You see, the video on DVDs is scrambled. Windows and Macintosh DVD players licensed by the DVD Copy Control Association contain the algorithms to unscramble the signal. The Linux DVD player contains these secrets as well. But since the Linux-based program isn't licensed, using the software constitutes an illegal circumvention of copyright management.

Things have gotten nasty as this new crime gets its tryout in the legal system. Last year, eight major film studios, all members of the Motion Picture Association of America, sued the magazine 2600 for posting on its Web site a program that unscrambles DVDs. Not only did the organization win its case, but U.S. District Court judge Lewis A. Kaplan even barred 2600 from posting links to other sites that contained the program. That case is now on appeal.

For the movie industry, the DVD case is about piracy and revenue protection. For the programmers among us, the attempts to suppress this software are an attack on fundamental freedoms of speech and inquiry. It is a battle the movie industry is sure to lose. The only question is, "when?"

At the core of the controversy is technical data about the copy protection techniques used to make DVDs. The information on each DVD is protected by an encryption scheme called the Content Scramble System, or CSS. This technology prevents computer users from duplicating a movie, compressing it down to fit on a CD-ROM, and then giving copies to their friends. Playing the DVD entails decrypting the data-an act that used to require a licensed DVD player with the appropriate descrambling algorithms, stored either in a program or in a set-top box.

Then in 1999, an anonymous European programmer cracked the code and distributed a program-called DeCSS-over the Internet. Ever since, the movie industry has been filing lawsuits and sending threatening letters to individuals and businesses that distribute this and related DVD decryption programs.

How did we get here? In the 1980s, compact discs revolutionized high- fidelity sound. But CDs were not well suited for movies: their roughly 600 megabytes could store barely 10 minutes of video. (Advanced compression systems can put an entire movie on a CD, but the quality suffers.)

Enter DVDs, which can store more than two hours of compressed video on a disc the same size as a CD. If you want to make your own DVDs, you can buy a recording drive for less than $500. Rewritable discs that hold 4.7 gigabytes cost about $30.

It's easy to see why the movie studios are worried. The price of recordable DVD discs is sure to fall. Three years ago, writable CD-ROMs cost $2; today, they're 40 cents or less. Expect writable DVDs for $5 by mid-2002. Equipped with programs like DeCSS, consumers will be able to make high-fidelity copies of DVDs on the cheap.