[HN Gopher] Cryptography in Home Entertainment (2004)
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Cryptography in Home Entertainment (2004)
Author : rvnx
Score : 77 points
Date : 2026-03-18 21:29 UTC (3 days ago)
(HTM) web link (mathweb.ucsd.edu)
(TXT) w3m dump (mathweb.ucsd.edu)
| janci wrote:
| How was CSS supposed to protect against copying the encrypted
| data? We should not need to decrypt the video to duplicate the
| disc.
| wmf wrote:
| 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 wrote:
| 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
| anthk wrote:
| I could rip PSX games just fine with cdrdao.
| phire wrote:
| 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 wrote:
| 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.
| dddgghhbbfblk wrote:
| It's implemented in drive firmware, so the drive will refuse to
| read protected sectors without authentication.
| beagle3 wrote:
| 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 wrote:
| >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 wrote:
| 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 wrote:
| 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 wrote:
| A sticker on the data side of the disc, then! Removing the
| sticker is a process.
| eesmith wrote:
| A sticker is not required for the ordinary course of its
| operation.
| hedora wrote:
| 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 wrote:
| 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 wrote:
| 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.
| miki123211 wrote:
| How are today's scene rippers about keeping extra audio
| tracks and such in these, E.G. audio description?
|
| It used to be quite hard to get an actually actually
| unmodified disc image.
| progbits wrote:
| On private trackers where people care about that stuff
| it's easier. The NFO usually has a pretty comprehensive
| description of the contents and all the tracks etc so you
| can decide which version you want before downloading.
| dddgghhbbfblk wrote:
| Unmodified Blu-ray disc images are the BDMV folders I
| mentioned. Any BDMV will be unmodified almost all the
| time though I've very occasionally run into modified ones
| originating from the Chinese piracy scene that had custom
| subs added.
|
| A "good" remux is actually the highest quality movie
| release available, usually, if you don't care about file
| size. A good remux will combine all the best parts of
| every possible release into one super-file. For one
| movie, you could have the best video quality be on a
| French UHD Blu-ray, the best audio quality from a
| different source, subtitles aggregated from various
| international releases and streaming platforms (and
| filtered/deduped for quality), chapter titles taken from
| an old DVD, and all available commentary tracks
| collected. Rarely you might even see a hybrid release
| where multiple streams are spliced together to fix some
| problem or another in one of them. You can look for
| releases by the CINEPHILES p2p group for gold standard
| examples, they get distributed fairly widely so you can
| probably find some.
|
| To answer what you asked about extra audio tracks
| specifically (outside of full disc images)--usually non-
| English dubs are considered bloat and aren't distributed.
| Commentary tracks are kept. Audio description is a mixed
| bag, good groups will keep it.
| ThrowawayTestr wrote:
| 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.
| gsich wrote:
| codec? x264 and 1080p is in the ~8GB range for a 120min
| movie. Depending on audio might be more.
| recursivecaveat wrote:
| 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.
| stevekemp wrote:
| Same story here, I can be used films on DVD for EUR1 at many
| charity shops. Boxed sets of TV shows are EUR2-5 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.
| 1317 wrote:
| > 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
| adrian_b wrote:
| 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.
| 1317 wrote:
| 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
| orsorna wrote:
| I think the more pressing issue is the medium degrading
| before the playback hardware. Disks have an average
| lifespan of 25 years. I surmise basic bluray hardware will
| last much longer.
| bob1029 wrote:
| The laser diode would probably be the first thing to fail
| in the player, and it likely wouldn't take 25 years if it
| was being used regularly.
| ThrowawayTestr wrote:
| I just torrent everything. It's equally as illegal.
| flomo wrote:
| 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.
| adrian_b wrote:
| 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 wrote:
| 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.
| pocksuppet wrote:
| You're not the average consumer. The average consumer is less
| likely to buy a DVD if they can pirate it, not more.
| maccard wrote:
| The average consumer won't pirate it unless it's easier to
| obtain the pirated copy than a legit version. They'll
| suffer through ads, poor quality, high prices. A good
| example is music - I'd bet audio piracy is bordering on a
| rounding error of 0 because of Spotify, Apple Music and YT
| music. Meanwhile, for video content you need to subscribe
| to Netflix, Prime, Hulu, Apple TV, and even then you won't
| get access to all of the "big" shows. Sky sports and co
| show that the vast majority of people are willing to pay
| for the content but when the service and availability
| suffers they'll go elsewhere
| mike_hearn wrote:
| You massively underestimate how price sensitive the
| average person is. Stuff like Spotify ended music piracy
| by driving the cost of music to nearly zero.
| anthk wrote:
| Audio CD's where no DVD's. You are confusing concepts there.
| flomo wrote:
| > 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 wrote:
| 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.
| flomo wrote:
| 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 wrote:
| 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.
| _-_-__-_-_- wrote:
| 09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0 /s
| y7 wrote:
| The link to cryptanalysis details is no longer working. Here's an
| alternative:
| https://www.cs.cmu.edu/~dst/DeCSS/FrankStevenson/analysis.ht...
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