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Topic: Who will supply digital content?
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Mark J. Marshall
Film God
Posts: 3188
From: New Castle, DE, USA
Registered: Aug 2002
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posted 12-28-2005 12:12 PM
I'm guessing that if that happens, the films will be encrypted one time, with one encryption key. That one encrypted copy of the movie will be sent to everyone, and the key to unlock it will be encrypted with the projectors' keys. (For all I know, that may be the way it's done now.) I'm basing my assumption on the movies themselves probably being anywhere from 50 to 150 GB each, so encrypting that amount of data 1000 times and keeping track of it all would just be ridiculous. Not to mention broadcasting it all over a satelite would be practically impossible since you know they're going to want to broadcast it no sooner than about six hours before show time.
To compromise that setup, one would need to 1) steal a particular projector's key (which could easily be discarded and recreated if it's ever discovered to be stolen), 2) intercept a particular film's encrypted key file for that projector, 3) obtain the encrypted data which was broadcast from the satelite (and the transmission itself will also likely be encrypted to a different key each time, so you will need access to that), and 4) be able to play back the data somehow and record it in a standard format.
All of those things are doable, but if all of the keys change on a regular basis, it will be difficult to keep up with them unless you're on the inside. Of course, we all know that the pirated material comes from inside Hollywood now via screener DVDs and such. So the short answer to your question is - it won't be easy for the average Joe Hacker, but it won't take long for existing pirates to adapt to the new model either. Not that they will need to. I'm sure screener DVDs will still be in use.
For what it's worth, that's my guess.
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John Hawkinson
Film God
Posts: 2273
From: Cambridge, MA, USA
Registered: Feb 2002
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posted 12-28-2005 05:39 PM
Mark,
There are several techniques that can be applied to make it much harder. For instance, they can make it so it is *almost* as if each movie is encrypted with a per-projector key.
A method to do this is to encrypt the movie once with a single key (A), and then encrypt that key (A) using a per-projector (Bnnn). Let's say that the per-projector key (Bnnn) is stored in tamper-proof hardware inside the digital projector. The movie and keylist get delivered to the projector (via satelite or whatever), the projector decrypts the key list with Bnnn and then now it has A, but A is inside the projector where you can't get at it. It then decrypts the movie with A and displays it (probably on an encrypted digital link from the decryptor box to the actual projector hardware).
Also, I don't think that encrypting a 150GB movie (isn't that a small estimate? but whatever) 1000 times would be difficult to *track*. I think the only real reason to avoid is is that sat. uplink time is expensive and they want to be able to broadcast the same datastream to all theatres, rather than an individual data stream per-theatre.
There are more complex methods available, too.
--jhawk
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Mark J. Marshall
Film God
Posts: 3188
From: New Castle, DE, USA
Registered: Aug 2002
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posted 12-28-2005 09:27 PM
quote: John Hawkinson
For instance, they can make it so it is *almost* as if each movie is encrypted with a per-projector key.
A method to do this is to encrypt the movie once with a single key (A), and then encrypt that key (A) using a per-projector (Bnnn). Let's say that the per-projector key (Bnnn) is stored in tamper-proof hardware inside the digital projector. The movie and keylist get delivered to the projector (via satelite or whatever), the projector decrypts the key list with Bnnn and then now it has A, but A is inside the projector where you can't get at it. It then decrypts the movie with A and displays it (probably on an encrypted digital link from the decryptor box to the actual projector hardware).
quote: Mark J. Marshall
I'm guessing that if that happens, the films will be encrypted one time, with one encryption key. That one encrypted copy of the movie will be sent to everyone, and the key to unlock it will be encrypted with the projectors' keys.
Didn't we just say the same thing? I think we're on the same page on that.
quote: John Hawkinson
(isn't that a small estimate? but whatever)
Possibly. I was going by someone on here who said that the 3D Chicken Little movie was about 80+ GB, which was an hour and a half long x2 eyes. My point about keeping track of (which I should have said "storing") 1000 copies of 150 GB of data was - why do that? It's ridiculous, and unnecessary. Encrypt the movie once, then focus on getting the keys encrypted and distributed.
I agree that once it's inside the projector, it could be next to impossible to get it out. The question presented was how long before the satelite signal is hacked.
Paul, What you're describing is exactly the way the system John and I are talking about would work, so maybe they're doing that already. If they're actually going through the trouble of encrypting the movie separately for each projector, I'd be surprised. That's way unnecessary overkill.
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David Buckley
Jedi Master Film Handler
Posts: 525
From: Oxford, N. Canterbury, New Zealand
Registered: Aug 2004
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posted 12-29-2005 12:24 PM
Encryption for movies is interesting; the "strength" of a particular cipher used is generally measured by how much effort using available computing power it takes to crack, and as long as the number is improbable with technology available within the time when the data must be secured, then its usually considered "strong enough".
It's possible, however, that some group of nutters may harness millions of PCs in an attempt to force a "brute force" attack, in a manner never previously attempted, and they may actually suceed.
The ultimate solution, of course, is one time pads, send out a CD to each recipient which is the unravel key for the encrypted movie sent by satellite. As there is no cipher alogrithm, theres nothing to crack: you either have the decoder ring, or you dont. Then as pointed out previously use double encryption for individual playback system control. You've still got distribution hassles, but a CD key is a logistically smaller problem than a full movie.
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Mark J. Marshall
Film God
Posts: 3188
From: New Castle, DE, USA
Registered: Aug 2002
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posted 12-30-2005 10:01 AM
I think encryption in general is really interesting, but it's tough to get your arms around some of the concepts. Most of the people who are really good with encryption are people who only work with encryption and nothing else. I had to learn PGP at my real job, and it took about two months to fully digest all of the intricacies and key relationships and all of that. The most interesting part was learning how to split a powerful key into multiple pieces so no one person could use it. What the program presents to the user and what is actually happening are two very different things, and I found that pretty cool.
But anyway back to the topic...
quote: Mark Hajducki
why would they not send the files out by satelite a few days in advance
Because they're paranoid, and it will probably take them a while to trust the encryption. They may never fully trust it.
quote: David Buckley
some group of nutters may harness millions of PCs in an attempt to force a "brute force" attack, in a manner never previously attempted, and they may actually suceed.
But unless they actually break the algorythm itself, or compromise an important key along the way, they'll have to start over each time and by the time they succeed, the movie will be out on DVD anyway.
quote: David Buckley
The ultimate solution, of course, is one time pads, send out a CD to each recipient which is the unravel key for the encrypted movie sent by satellite.
One time pads are the only true "unbreakable" encryption algorythm because as you said, there is no algorythm, and there's nothing to break. But I think trusting that the CDs won't get copied at the theater and broadcast all over the Internet isn't a good idea. One time pads are only really reliable if you're dealing with very small groups of participants.
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