qrpff Explained

qrpff.pl is an obfuscated Perl program, written by Keith Winstein and Marc Horowitz of MIT. It decodes CSS, the content scrambling system used to encode video data on DVDs.

Wired magazine recently asked me to write a short article explaining how qrpff.pl worked. Wired being what it is, I knew that no matter how little informative content I actually included, it would be too much---they would assiduously remove all actual information from my article, and the result would be a piece which would give the reader a warm fealing of having understood, but without actually imparting anything else of value. That's what Wired is about: The illusion of knowledge without any of the difficult bits. Sure enough, that is what happened. The result is on page 78 of the June 2001 issue if you want to see. (The print version discusses a somewhat shorter and more obfuscated version of qrpff that became available later on.)

Here's the original draft I sent.

Note that this article may not be online for long. Under a grossly immoral law with the ridiculous title 'Digital Millennium Copyright Act', I may be forbidden to even discuss the operation of this program. See David Touretzky's DeCSS Web Pages for many interesting details about CSS and DMCA. Here's some recent news.

qrpff Explained
Here's the Wired version

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