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>> Also it probably has some checksum, you'd need a shed load of stamps to
>> figure it out probably.
>
> Well, if you were going to reverse-engineer it, sure. But if you could
> figure out the algorithm...
How are you going to figure out the algorithm without access to lots of
stamps you know are valid?
> If you *knew* how they generate the barcode, you could put an arbitrary IP
> address in there.
Isn't the problem here that you're trying to work out how to generate the
barcode?
>> A bit like that system on Blu-Ray discs, where every player plays back a
>> very slightly different version, so when someone rips and uploads to
>> BitTorrent, they can tell exactly which player it was ripped from.
>
> Really? That's news...
http://www.freedom-to-tinker.com/tags/aacs?page=1
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>>> Also it probably has some checksum, you'd need a shed load of stamps
>>> to figure it out probably.
>>
>> Well, if you were going to reverse-engineer it, sure. But if you could
>> figure out the algorithm...
>
> How are you going to figure out the algorithm without access to lots of
> stamps you know are valid?
I suppose the fatal assumption here is that the encoding of the
information into the barcode is trivial. If these guys are sensible, it
won't be...
>>> A bit like that system on Blu-Ray discs, where every player plays
>>> back a very slightly different version, so when someone rips and
>>> uploads to BitTorrent, they can tell exactly which player it was
>>> ripped from.
>>
>> Really? That's news...
>
> http://www.freedom-to-tinker.com/tags/aacs?page=1
Interesting. So the film actually ends a different way depending on
which player you play it with?
I bet that'll be popular...
[But then again, all these copywrite notices and "piracy is stealing"
ads and aggressive copy-protection systems only piss off paying
customers. They have no effect on criminals...]
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> Interesting. So the film actually ends a different way depending on which
> player you play it with?
>
> I bet that'll be popular...
LOL, I suspect they can do it slightly more subtly than that! They only
need to make some tiny changes to some of the pixels to be detectable. In
theory they could do what you suggest though, would be fun :-)
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>> Interesting. So the film actually ends a different way depending on
>> which player you play it with?
>>
>> I bet that'll be popular...
>
> LOL, I suspect they can do it slightly more subtly than that! They only
> need to make some tiny changes to some of the pixels to be detectable.
> In theory they could do what you suggest though, would be fun :-)
Well, the article states that it's supposed to resist somebody pointing
a video camera at their TV screen, so a 1-pixel alteration won't do.
What I suppose they might do is have maybe a 1-frame difference in how
long a given scene is. Like, on some disks the shot of the ocean is 1362
frames long, and on others it lasts for 1366 frames. The difference
should be reliably detectable no matter how you film it.
Still, it seems like a hell of a lot of work considering that it doesn't
actually stop illegal copying, it just makes it hypothetically possible
to find out who did the illegal copying...
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scott wrote:
> BitTorrent, they can tell exactly which player it was ripped from.
With the understnading that a "player" in this context means "model number"
at least in the hardware players. I.e., they can tell it got ripped by a
Sony XYZ-1230 brand blu-ray player, not Joe's blu-ray player.
The idea is to identify it enough to black list the leaked keys, not to
catch the person who distributed the movie.
--
Darren New, San Diego CA, USA (PST)
I ordered stamps from Zazzle that read "Place Stamp Here".
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Invisible wrote:
> Well, the article states that it's supposed to resist somebody pointing
> a video camera at their TV screen, so a 1-pixel alteration won't do.
Probably different watermarks encoded, without actually looking visibly
different in a way you could tell. Otherwise, someone might just rip it
twice and change the file to use (say) 1364 frames of ocian.
--
Darren New, San Diego CA, USA (PST)
I ordered stamps from Zazzle that read "Place Stamp Here".
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>> Well, the article states that it's supposed to resist somebody
>> pointing a video camera at their TV screen, so a 1-pixel alteration
>> won't do.
>
> Probably different watermarks encoded, without actually looking visibly
> different in a way you could tell. Otherwise, someone might just rip it
> twice and change the file to use (say) 1364 frames of ocian.
Well, to lots of people digital watermarking is the Holy Grail of
digital technology, the thing that will finally stop the pirates.
Trouble is... it's extremely hard.
If the watermark is encoded in a way that's perceptually
insignificant... well guess what lossy codecs are specifically designed
to do? Yes, that's right: *remove* perceptually insignificant information!
I'm thinking things like small timing differences would be too subtle to
notice, but significant enough for encoding to not screw them up. And
you could try to correct it yourself, but you'd have to know exactly
which bits of timing are varied in order to know what to change...
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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>> BitTorrent, they can tell exactly which player it was ripped from.
>
> With the understnading that a "player" in this context means "model
> number" at least in the hardware players. I.e., they can tell it got
> ripped by a Sony XYZ-1230 brand blu-ray player, not Joe's blu-ray player.
>
> The idea is to identify it enough to black list the leaked keys, not to
> catch the person who distributed the movie.
The article suggests that the system *is* supposed to be able to narrow
it down to a specific machine or possibly a small number of such
machines, not just a specific model.
Of course, it depends on whether the makers bother to fit each player
with semi-unique keys or not... One commenter pointed out that hardware
manufacturers have no vested interest in making DRM work. Only studios do.
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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Orchid XP v8 wrote:
> Trouble is... it's extremely hard.
Certainly.
> If the watermark is encoded in a way that's perceptually
> insignificant... well guess what lossy codecs are specifically designed
> to do? Yes, that's right: *remove* perceptually insignificant information!
Well, you can spread it across lots of media, a few bits at a time. Xerox
had a mechanism where you could vary the spacing between words in a
document, and encode maybe a couple dozen bits per page of a document, for
example.
But yes, it's difficult. Anything else is open to fairly simple subversion,
tho.
> I'm thinking things like small timing differences would be too subtle to
> notice, but significant enough for encoding to not screw them up.
Could be, until you convert PAL to NTSC. :-) What you'd want is to have
something where it's difficult without the key to even know where the data
is encoded.
> you could try to correct it yourself, but you'd have to know exactly
> which bits of timing are varied in order to know what to change...
But you have the different pieces all on the disk. All you need is the keys
from two different players and you can tell what's different.
--
Darren New, San Diego CA, USA (PST)
I ordered stamps from Zazzle that read "Place Stamp Here".
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Orchid XP v8 wrote:
> The article suggests that the system *is* supposed to be able to narrow
> it down to a specific machine or possibly a small number of such
> machines, not just a specific model.
No, that's what I'm saying. "Player" in *this* context means a set of keys
(obviously). Software players can each get a set of keys from the
manufacturer when you install the machine. But people don't, in general,
program a unique key into each hardware player.
--
Darren New, San Diego CA, USA (PST)
I ordered stamps from Zazzle that read "Place Stamp Here".
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