Cryptography in Home Entertainment (2004)
49 points by rvnx 3 days ago | 29 comments

flomo 4 hours ago
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.

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adrian_b 4 hours ago
It was good that CSS was a lousy scheme, for everybody, including for the DVD producers.

As long as CSS was not broken, I bought neither discs nor drives, because I believe that only naive customers (to not say losers) are willing to buy any kind of information that cannot be protected from the certain eventual destruction due to the decay of its storage medium, by making copies of it on any other kind of storage medium.

After CSS was broken and the tools to read DVDs became available publicly, I have bought several DVD drives during the following years and many hundreds of DVDs.

So the breaking of the CSS was how the DVD industry got my money, and presumably the money of many others. They should have been grateful to the one who did this.

When you "buy" copy-protected information you are not really buying it. You are just renting it until the time when its storage medium will become corrupt, which is certain to happen, sooner or later. (Or until your reader becomes defective and you can no longer buy a replacement, due to obsolescence.)

The copyright laws are stupidly named and frequently stupidly formulated. Making copies not only is not a crime, but it is a fundamental right of the owner of any kind of information, being the only way in which information can be preserved.

Only the distribution of copies to third parties may be criminalized. While most stupid copyright laws claim that even making copies by the owner is a crime, that is not only unjust but it also not enforceable against any careful owner, so the laws are doubly stupid.

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pocksuppet 2 hours ago
You're not the average consumer. The average consumer is less likely to buy a DVD if they can pirate it, not more.
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flomo 3 hours ago
Good for you. Good for the guy who sold disks at the flea market too.

DVDs/BRs/etc were always a scam imo, unless it your favorite movie that you will watch repeatedly forever. For most people buying DVDs was just expensive PPV.

As they say, piracy is a service issue.

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anthk 3 hours ago
Audio CD's where no DVD's. You are confusing concepts there.
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hedora 6 hours ago
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.

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recursivecaveat 5 hours ago
I used to not be a physical media person. I have found that it makes it a lot easier for me to start and to finish things though. The fact I have to actually get up to swap the disk out if I want a distraction helps focus the attention span haha.
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stevekemp 5 hours ago
Same story here, I can be used films on DVD for €1 at many charity shops. Boxed sets of TV shows are €2-5 depending on size/popularity.

The only downside is that I've noticed that the used DVD sections are definitely getting smaller. I guess fewer people are donating their collections these days.

I've bought a couple of DVD sets from Amazon, used, but the prices there aren't so competitive. Still it's nice to have physical media, with real/original soundtracks.

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1317 3 hours ago
> The easiest way to play those BluRays back

buy a bd player? i don't know why you would settle on a usb rw drive when you could just have a box that plugs in via HDMI and works

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adrian_b 3 hours ago
A bd player is a temporary solution.

At some point nobody will make bd players any more. Several big companies have already stopped production.

Then you would have a useless BluRay collection after your own player stops working.

The solution is of course to rip off the BluRay discs as soon as you buy them. Then you can have a higher-quality playback on a PC (due to much faster random access and sequential access on an SSD) and you can recopy them forever when the available storage media will change in the future, so you will not lose what you have paid for.

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1317 3 hours ago
and all existing players will disappear off the face of the earth never to grace the listings of ebay again

come on man

people can complain about the dvd/bd scrambling restricting your freedoms and stopping you from making backups etc, and sure that's true

but if you just want to sit in front of the tv and watch a film you bought, idk what more you could ask for

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MathMonkeyMan 6 hours ago
How many GB? I see "bluray rip" mp4 files on torrent index sites, which I assume have been aggressively recompressed, but there are three size tiers in the "1080p" category: 2-3GB, 7-10GB, and 15+GB.
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dddgghhbbfblk 6 hours ago
You want to search for BDMV for full disc images, or for remuxes which are uncompressed video and audio streams, if you want to get a sense for the size on disc. Typical Blu-ray images will be from 20-40ish GB.
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ThrowawayTestr 3 hours ago
It really depends on your hard drive space and your tolerance for compression. Two hours of decently compressed video is a few gigs, but if you want 10-bit HDR with 5.1 audio, then choose the 15 gig torrent.
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ThrowawayTestr 3 hours ago
I just torrent everything. It's equally as illegal.
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flomo 3 hours ago
> 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.

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anthk 3 hours ago
Internet says nothing about that; and using VB for DeCSS it's as 'serious' as quickly hacking Perl or TCL (for its day) in order to complete a simple prototype.

If any I can just see C++ code which is pretty much portable because you can decouple I/O with ease, altough under Unix you would need to use ioctl's to command the DVD drive in a low level way.

https://github.com/cthpw103/decss

But for just decoding a dumped ISO Perl would be more than enough, from parsing UDF headers to unscramble the media.

It would last hours instead of 15 minutes under my Athlon 2000 but if would work the same.

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flomo 2 hours ago
VB could bang on any Win32 C API, so there's no reason to disbelieve this. In the modern sense it's like saying you couldn't write this in Go. Direct question: do you know what you are talking about, or are you just spewing keywords and reddit mime dancing?
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janci 6 hours ago
How was CSS supposed to protect against copying the encrypted data? We should not need to decrypt the video to duplicate the disc.
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wmf 6 hours ago
Keys were stored on an area of the disc that wasn't writable on DVD-Rs so you couldn't copy the whole disc.
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phire 2 hours ago
It was apparently hidden in the lead-in area, but I can't find any information on how it was encoded. Some sources say "a hidden sector in the lead in" but that doesn't seem right, as there is nothing physically stopping a DVD burner with custom firmware from writing a hidden sector.

The disk key is small (40 bits) and I'm suspicious it's actually encoded as wobble frequency [0], like the PS1's copy protection scheme.

Because CD/DVD burners can't write wobble. Blank CDs/DVDs ship with a pre-made wobble in the pre-groove, which the burners use to determine the absolute position of the write laser.

[0] *https://en.wikipedia.org/wiki/Wobble_frequency

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dddgghhbbfblk 5 hours ago
It's implemented in drive firmware, so the drive will refuse to read protected sectors without authentication.
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beagle3 4 hours ago
That was a late edition. I have working DVD drives that will happily read anything on a disc, even if they can’t decode it.

Newer drives I bought will refuse reading what they won’t decide themselves (e.g. wrong region).

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charcircuit 6 hours ago
>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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gzread 5 hours ago
See also farmers repairing their tractors. Arguably you can just write DO NOT COPY on a sticker on the disc and then it's illegal to circumvent the sticker.
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eesmith 3 hours ago
In the US the law makes it illegal to 'circumvent a technological measure', defined as:

> descramble a scrambled work, to decrypt an encrypted work, or otherwise to avoid, bypass, remove, deactivate, or impair a technological measure, without the authority of the copyright owner

where

> a technological measure “effectively controls access to a work” if the measure, in the ordinary course of its operation, requires the application of information, or a process or a treatment, with the authority of the copyright owner, to gain access to the work.

A sticker doesn't count as a "technological measure".

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pocksuppet 2 hours ago
A sticker on the data side of the disc, then! Removing the sticker is a process.
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eesmith 49 minutes ago
A sticker is not required for the ordinary course of its operation.
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_-_-__-_-_- 2 hours ago
09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0 /s
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