4 ms·

Cryptography in Home Entertainment (2004)

82 points by rvnx 7mo ago

_-_-__-_-_- 7mo ago
09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0 /s
janci 7mo ago
How was CSS supposed to protect against copying the encrypted data? We should not need to decrypt the video to duplicate the disc.
- wmf 7mo 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.
  - phire 7mo 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 https://en.wikipedia.org/wiki/Wobble_frequency
    - anthk 7mo ago
      I could rip PSX games just fine with cdrdao.
      - phire 7mo ago
        But you couldn't rip the copy protection signal (not that you needed to, it was a fixed 4 letter string, "SCEA", "SCEI", or "SCEE" depending on region) Nor could you burn it onto a CD-R. It was there to prevent people from burning copies of games, not to prevent you from ripping the disc. Of course, it was stupidly easy to bypass with a mod chip. They literally just sit there injecting the copy protection signal into the cd rom electronics, tricking it into thinking every single disc was blessed by Sony, burned or not.
        anthk 7mo ago
        Not needed for emulation. I never owned a PSX so I used EPSXE and whatever I got for the N64 in early 2000s. I jumped from a GB/NES in late 90's to a PC. It was like crossing a wormhole to another dimension.
        phire 7mo ago
        In this era, console designers were't concerned about emulators or ripping games. They were entirely focused on preventing game duplication (especially with CDs being so easy to copy) and unlicensed games. And the PS1's copy protection makes an ok effort at being a roadblock to running non-sony discs. In fact, the question of emulators wouldn't have been on the Sony engineers minds at all. Because in 1994 (when the ps1 launched) there were no viable console emulators. There were a few early prototypes, but they didn't produce 'playable results'. The first viable emulator (for any console) was arguably NESticle, released in April 1997. Things then moved rapidly, we see the first viable 16bit emulators in 1998. It's notable that the PS2 doesn't have any protection against ripping games either. The Sony engineers would have been aware of emulators by this point, but they might have assumed that emulation would be stuck in the 8/16bit era for the foreseeable future. So it must have been a huge shock for the first viable 32bit era emulators to come out in 1999. Connectix Virtual Game station (Jan 1999), UltraHLE (Also Jan 1999) and Bleem! (March 1999) Yes.. that's right. We went from the first viable NES emulator to viable PS1/N64 emulators in under 2 years. I'm guessing the PS2 was a little too close to it's March 2000 release date at this point to slap on rip protection, but the Gamecube and Xbox were released 18 months later, and both had time to implement disc encryption schemes.
- dddgghhbbfblk 7mo ago
  It's implemented in drive firmware, so the drive will refuse to read protected sectors without authentication.
  - beagle3 7mo 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).
charcircuit 7mo 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.
- gzread 7mo 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.
  - eesmith 7mo 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".
    - pocksuppet 7mo ago
      A sticker on the data side of the disc, then! Removing the sticker is a process.
      - eesmith 7mo ago
        A sticker is not required for the ordinary course of its operation.
hedora 7mo 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.
- MathMonkeyMan 7mo 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.
  - dddgghhbbfblk 7mo 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.
flomo 7mo 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 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.
- adrian_b 7mo 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.
  - flomo 7mo 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.
flomo 7mo 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.
- anthk 7mo 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 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.
  - flomo 7mo 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?
    - anthk 7mo ago
      So did Perl with bindings and TCL interoperating in two ways. Reddit? I used to compile mplayer and libdvdcss long ago, and even if the prior version was VB/C++ bound, it was the open code (FLOSS) the one who survived every takedown attempt. The same with Nagra encoding and XawTV for some propietary channels in TV. You can decode any stream (and even extract subtitles) thanks to free software. Even BTTV cards will still work. Go try that with Windows 7 and up. If you can find drivers, that's it. And working decoding software not messing up with DDraw based codecs and rendering. I was there, and it was the free software the one who broke most of the chains. Propietary software today it's useless.
y7 7mo ago
The link to cryptanalysis details is no longer working. Here's an alternative: https://www.cs.cmu.edu/~dst/DeCSS/FrankStevenson/analysis.html https://www.cs.cmu.edu/~dst/DeCSS/FrankStevenson/analysis.ht...
badcarbine 7mo ago
[dead]

82 points by rvnx 7mo ago

09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0 /s

janci 7mo ago

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

wmf 7mo 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.
- phire 7mo 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 https://en.wikipedia.org/wiki/Wobble_frequency
  - anthk 7mo ago
    I could rip PSX games just fine with cdrdao.
    - phire 7mo ago
      But you couldn't rip the copy protection signal (not that you needed to, it was a fixed 4 letter string, "SCEA", "SCEI", or "SCEE" depending on region) Nor could you burn it onto a CD-R. It was there to prevent people from burning copies of games, not to prevent you from ripping the disc. Of course, it was stupidly easy to bypass with a mod chip. They literally just sit there injecting the copy protection signal into the cd rom electronics, tricking it into thinking every single disc was blessed by Sony, burned or not.
      - anthk 7mo ago
        Not needed for emulation. I never owned a PSX so I used EPSXE and whatever I got for the N64 in early 2000s. I jumped from a GB/NES in late 90's to a PC. It was like crossing a wormhole to another dimension.
        phire 7mo ago
        In this era, console designers were't concerned about emulators or ripping games. They were entirely focused on preventing game duplication (especially with CDs being so easy to copy) and unlicensed games. And the PS1's copy protection makes an ok effort at being a roadblock to running non-sony discs. In fact, the question of emulators wouldn't have been on the Sony engineers minds at all. Because in 1994 (when the ps1 launched) there were no viable console emulators. There were a few early prototypes, but they didn't produce 'playable results'. The first viable emulator (for any console) was arguably NESticle, released in April 1997. Things then moved rapidly, we see the first viable 16bit emulators in 1998. It's notable that the PS2 doesn't have any protection against ripping games either. The Sony engineers would have been aware of emulators by this point, but they might have assumed that emulation would be stuck in the 8/16bit era for the foreseeable future. So it must have been a huge shock for the first viable 32bit era emulators to come out in 1999. Connectix Virtual Game station (Jan 1999), UltraHLE (Also Jan 1999) and Bleem! (March 1999) Yes.. that's right. We went from the first viable NES emulator to viable PS1/N64 emulators in under 2 years. I'm guessing the PS2 was a little too close to it's March 2000 release date at this point to slap on rip protection, but the Gamecube and Xbox were released 18 months later, and both had time to implement disc encryption schemes.
dddgghhbbfblk 7mo ago
It's implemented in drive firmware, so the drive will refuse to read protected sectors without authentication.
- beagle3 7mo 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).

charcircuit 7mo 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.

gzread 7mo 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.
- eesmith 7mo 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".
  - pocksuppet 7mo ago
    A sticker on the data side of the disc, then! Removing the sticker is a process.
    - eesmith 7mo ago
      A sticker is not required for the ordinary course of its operation.

hedora 7mo 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.

MathMonkeyMan 7mo 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.
- dddgghhbbfblk 7mo 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.

flomo 7mo 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 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.

adrian_b 7mo 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.
- flomo 7mo 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.

flomo 7mo 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.

anthk 7mo 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 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.
- flomo 7mo 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?
  - anthk 7mo ago
    So did Perl with bindings and TCL interoperating in two ways. Reddit? I used to compile mplayer and libdvdcss long ago, and even if the prior version was VB/C++ bound, it was the open code (FLOSS) the one who survived every takedown attempt. The same with Nagra encoding and XawTV for some propietary channels in TV. You can decode any stream (and even extract subtitles) thanks to free software. Even BTTV cards will still work. Go try that with Windows 7 and up. If you can find drivers, that's it. And working decoding software not messing up with DDraw based codecs and rendering. I was there, and it was the free software the one who broke most of the chains. Propietary software today it's useless.

y7 7mo ago

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

badcarbine 7mo ago

[dead]