Cryptography in Home Entertainment (2004)

This is a fun rabbit hole to walk down.

You might have noticed that streaming is getting worse (more expensive, less selection, more ads, more fragmentation). For me, they crossed a breaking point, where I decided I'd just find something more convenient.

So, I went down to the local record store, where they have 10,000s of DVDs and Blu Rays in stock; many for $1 (DVD), $2 (BluRay), most under $5-10, and a few gems for $20-30. The prices are for a mix of new and used DVDs; some new DVDs are over-printed, and cost $1.

Problem half-solved. I looked around to figure out how to play these anachronistic shiny disks on my TV, and eventually settled on a USB BluRay RW drive (I guess you can get rewritable BluRays!)

I never figured out how you're supposed to actually use that drive to play movies. Instead, there's DeCSS from the article, then something comparable for BluRay. For the "easy" decryption, you end up downloading per-disk decryption keys for every disk ever printed.

For the more advanced stuff, they have this giant Java Rube Goldberg machine that xors glitches into the video stream. This gets applied at the factory, and then (on some hardware I guess you can purchase?) again via some complicated JVM stack that was originally meant to just render the scene selection menu.

[spoiler alert]

The easiest way to play those BluRays back is to just download the output of the Rube Goldberg machine. At some point the industry realized that scheme was dumb, so there's a finite set of glitch masks. The whole dataset for all BluRays that will ever be produced with this scheme is a few GB.

You might think that when I say "play", I mean "transcode + pirate", but it turns out that's not particularly practical. BluRays are multiple GB, and already compressed with codecs that are competitive with modern ones, so they don't shrink down like DVDs unless you're willing to lose a lot of quality.

So, yes, we have a growing collection of physical media. I target 20-30 movies / $100 when I go to the store. It's grand.

Worth noting the industry knew that CSS was a lousy scheme. Originally, Disney and others were boycotting DVD because of it. That lead to DIVX (the disk not the codec).

https://en.wikipedia.org/wiki/DIVX

Some people were opposed to DIVX's 'phone home' PPV option, but the bigger issue was it seemed like a nasty format war was brewing. Then DIVX flopped quickly. Instead, the MPAA got the US Congress to "patch" CSS by passing a law.

Apple had an advertising campaign that you could "Rip. Mix. Burn." your CDs with a Mac. Obviously nerds could rip DVDs, but nobody ever could productize it like that.

> The original reason behind the DVD scrambling system "needing" to be cracked was the lack of software DVD players for the Linux operating system.

Also, this is a false history, and more of an ex-post-facto justification.

The original DeCSS was a VisualBasic program written by some W1nd0z h8X0r teenager. Not for any greater cause, just because they could.

The link to cryptanalysis details is no longer working. Here's an alternative: https://www.cs.cmu.edu/~dst/DeCSS/FrankStevenson/analysis.ht...

How was CSS supposed to protect against copying the encrypted data? We should not need to decrypt the video to duplicate the disc.

>He hadn't pirated anything, only made a program to view his DVDs in Linux.

He released a tool for circumventing a protection measure. While already illegal to do in America, it wasn't made illegal in Norway until less than 2 years later.

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