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This topic comprises 6 pages: 1 2 3 4 5 6
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Author
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Topic: Change Over To Digital Cinema
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Mark J. Marshall
Film God
Posts: 3188
From: New Castle, DE, USA
Registered: Aug 2002
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posted 03-11-2005 11:41 AM
They can't possibly be encrypting gigabytes upon gigabytes of data over and over again for every single projector using different keys each time.
What they're likely doing is encrypting once and then that "content" key itself is encrypted with the projectors' public key. The projector then would decrypt the "content" key with its private key and then finally decrypt the content with the content key.
Now maybe on top of that, they create half a dozen different sets of content encrypted with different keys, and each projector gets one of the six. That could further frustrate hackers.
But a system like the one I just described would allow the projector to recreate its keys if they became corrupted or compromised at any point, and as long as you send the projector's public key to technicolor, they can re-encrypt the content key with it, send it to you in an email, and you could load it up and run the same content without having to reload it. In fact, maybe the projector recreates keys for each show. That's also possible. That would REALLY lock things up assuming that the projector's private keys are well protected in the software.
But anyway, my point is, the data would be encrypted ONCE with a common content key. Or perhaps half a dozen times with half a dozen different keys. But there is no way that the content is different for every projector. Encrypting ONCE with a common key would also allow a single transmission through a satelite to all the theaters. But then they would need to receive the encrypted content key through an email or some other way to actually unlock the content and play it.
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Bobby Henderson
"Ask me about Trajan."
Posts: 10973
From: Lawton, OK, USA
Registered: Apr 2001
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posted 03-11-2005 12:40 PM
quote: Ian Bailey
Imagine watching the Super Bowl in a nice warm theatre in Alaska
Knowing a bit about the pay per view marketplace, that's not likely to happen.
Regarding the Super Bowl specifically, that's a freely available network broadcast (at least it is here in the United States). Most people will watch that at home, or over at a friend's home. If they go to any commercial venue to watch it, they'll visit a restaurant or bar. Not very many movie theaters in this country will serve you beer and snacks during a big game.
The top customer of big pay per view broadcasts is bars. Nearly all the rest of the customer traffic is people ordering pay per view movies to watch at home.
Essentially, my point is people expect to watch movies in a movie theater. I don't think they're going to pay $7 to $12 to watch a sports program when they can watch the same thing at home for nothing or watch it for free in a bar.
Now it might be kinda cool to watch some championship game video-projected onto a large movie screen, particularly if the image is bright and the audio is well presented 5.1 surround. But that's still going to be more of a novelty. I think the viewer paradigms of throwing Super Bowl parties at home or watching the big game in a bar while getting piss drunk with your friends will be too hard to change.
quote: Paul Konen
Sure, a title will probably be cracked, but it will be hard for them because the keys change each time.
It doesn't surprise me anymore when hackers are able to crack some new "uncrackable" piracy keys. For instance, Adobe came up with their two-tiered software authentication system for Photoshop. The software has to be activated through Adobe's servers and a software version of a dongle is written to the boot sector of the computer's hard drive. The method sounded pretty bulletproof, but it probably didn't take a month before completely cracked copies of PhotoshopCS were showing up on various P2P sites. Needless to say, the next Adobe Studio CS package will have some updated anti-piracy scheme -likely to be cracked as fast, if not faster, the next time around.
Here's one idea for an anti-piracy measure for D-Cinema: get something done for that 4K standard and make it such that the movie requires an absolute ton of data to store. Not too many people are going to want to bother uploading or downloading a movie at all if it takes them a few 400GB hard discs to store it.
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John Hawkinson
Film God
Posts: 2273
From: Cambridge, MA, USA
Registered: Feb 2002
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posted 03-11-2005 02:01 PM
Paul says, "I imagine that is was the private side of the key and the data was encrypted with the public side of it, but it would have to be brute force cracked in order to decode. And then we are talking decoding gigabytes of data. Heck, even the new SW EP III trailer was over 1 GB in disk space."
DES, 3DES, and AES are all symmetric (aka conventional) encryption algorithms, not public-key. Generally in a public key system (like PGP email), the message is actually encrypted with a symmetric algorithm, and then the symmetric key (just the key!) is encrypted with a public-key algorithm.
In any case, the more data there is, the easier it is to attack the encryption.
Mark Marshall wrote, "They can't possibly be encrypting gigabytes upon gigabytes of data over and over again for every single projector using different keys each time."
Sure they can! They're probably burning individual DVDs already, rather than mass-producing them, and at that point, it's straightforward to re-encrypt the data as part of the burning process.
Scott: I assume that HD-SDI has some copy management features (like SCMS) so if a source sets the "Do Not Copy Me" bit, then an HDCAM deck will refuse to make a copy.
--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 03-11-2005 04:17 PM
quote: John Hawkinson
Sure they can! They're probably burning individual DVDs already, rather than mass-producing them, and at that point, it's straightforward to re-encrypt the data as part of the burning process.
Ugh. That just seems like a nightmare to manage if that's the case. And if digital projection ever becomes mainstream... I don't even want to think about the complexity of managing thousands of copies all keyed differently, and then doing that for EVERY release. Holy cow. ![[Frown]](frown.gif)
I also can't imagine them handing you the content encrypted with a symmetric key, and then also handing you the key. That's just stupid and doesn't make any sense at all security wise.
quote: John Hawkinson
In any case, the more data there is, the easier it is to attack the encryption.
Multiple copies of the SAME data all encrypted with different keys makes it easier too.
quote: John Hawkinson
I assume that HD-SDI has some copy management features (like SCMS) so if a source sets the "Do Not Copy Me" bit, then an HDCAM deck will refuse to make a copy.
I wonder how long it will be before someone produces one that will ignore that bit and copy it anyway. My guess is... not long.
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John Pytlak
Film God
Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000
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posted 03-14-2005 01:53 PM
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quote:
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quote:
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Steve Guttag
We forgot the crackers Gromit!!!
Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
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posted 03-18-2005 06:25 PM
Lets see...the easy stuff...
HD-SDI that is a standard ANSI/SMPTE definition and has nothing to do with DCinema other than DCinema is currently using it as the transmission medium from the server to the projector. It allows for Hi-Definition signals. Prior to that was SD-SDI which is just standard definition 480 lines. Most in the trade will just refer to SD-SDI as just "SDI" and HD as HDSDI. Both SDI and HDSDI can also have audio embedded in the signal too so a single coax can carry video and audio.
With the standard comes everything one needs to use it, like cabling and such. Since HDSDI has no problem with 1080p material up to 60Hz it has been a good choice and a standard.
Next comes the copy protection schemes. Within the industry, there is something that is called DCI or Digital Cinema Initiative. This little group is supposed to be laying the ground rules for all of the DCinema manufacturers so regardless of system, if the system is DCI compliant, the system will work.
Part of the DCI is copy protection. At no point during the video signal's transmission is the signal un encrypted. Thus, the "film" is transferred to the the theatre by various means in a totally encrypted form.
A DCI compliant system must have a key of some sort to authorize the player to play and partially un-encrypt the signal so it may be sent to the video projector. As I understand it, each player must be registered for the key to work and the key will work any player within the complex (so you may move a "film" without needing a different key).
Note I said partially decrypted. DCI also has this thing called the "Link" that has the video projector itself perform the final decryption. Thus, even and HDSDI monitor looking at the output of the player would not be able to provide a picture. The Link feature I believe is on the TI boards themselves (and will be on any DCI complient system). There is to be no viewable picture available at any point within the chain until final projection.
I don't know if this is part of the DCI, but one of the players will shut down if you open up the chassis and will require "Re authorization" before it can decode any futher material.
As to servicing Digital projectors? Yes, Mark, I've done that too...changed boards and everything. As to the grand/hour or grand/day...nope not there yet but getting there.
Steve
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