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How encryption for Cinema Movies works

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Re: How encryption for Cinema Movies works

#21

Post by andreashaerter »

I also recommend an insightful talk by the author of the article, delivered at a Chaos Computer Club (CCC) event (GPN, Gulaschprogrammiernacht) on this topic. Unfortunately, it's only available in German, but it's definitely worth watching: https://media.ccc.de/v/gpn22-382-kein-kinoerlebnis-ohne-korr...

„No cinema experience without correct certificate management... A look behind the scenes of a cinema with a digital projector system, how distributors deliver films to cinemas with end-to-end encryption, and how films are protected from piracy. In addition to an overview of projector technology, the presentation will demonstrate the file format and manual decryption of film data.“

Edit: I just realized that the author of the article also delivered the recorded talk, adapted my comment.

Re: How encryption for Cinema Movies works

#23

Post by jeffbee »

It's remarkable that they do all this in the context of box office revenues cratering. In 2024 American theaters has less gross ticket sales than they did in 1982, in constant dollars. The whole thing of movie theaters is just over.

Re: How encryption for Cinema Movies works

#24

Post by codemiscreant »

john01dav wrote: post #3

Even with all of this onerous encryption and DRM, it's not hard to find pirated copies of movies. It makes me think that the sacrifice in ownership rights for the theaters over their equipment isn't worth it.

There is essentially zero piracy from these digital cinema releases. The pirate copies are generally from once it starts digitally streaming on one of the services including PPV, and when pirate copies exist earlier it is almost always someone with a camera in a theatre making a terrible quality screener.

Piracy is inevitable, but in this case their model is much more robust that I would have predicted.

Re: How encryption for Cinema Movies works

#26

Post by thr0w »

mysteria wrote: post #20
kmeisthax wrote: post #12

Earlier quoted context omitted.

Hollywood is stupid and eroded its own economic advantage by putting everything on streaming. This was already known, but it also makes antipiracy operations much, much harder. Ripping a stream is always going to be easier than getting any unprotected video footage out of a movie theater. The stream is in your own home, you own and can tamper with all the equipment involved in playing it, and the economics of CDNs pr…

To be clear, traitor-tracing each stream would require a unique encode per account to inject the stegotext; that's computationally unfeasible. Doing one encode per movie theater would still be a struggle, but less so by three orders of magnitude. If the movie is streamed in chunks, only certain short segments would need to be reencoded to add watermark data. Alternatively it might be possible to splice in a short seg…

> If the movie is streamed in chunks, only certain short segments would need to be reencoded to add watermark data

Look into A/B watermarking - https://techdocs.akamai.com/adaptive-media-delivery/docs/add...

Re: How encryption for Cinema Movies works

#27

Post by thr0w »

coppsilgold wrote: post #17
perryflynn wrote: post #10

Earlier quoted context omitted.

It also contains watermarks. So theatres which failed to prevent recording will run into serious issues. See https://dcpomatic.com/forum/viewtopic.php?t=2372

If the software to watermark is widely available (as it appears to be) then an adversary has all they need to corrupt any existing watermark. These steganographic watermarks depend on no knowledge of the process. If the method is particularly ingenious (one of the inputs is centrally stored entropy which the extractor references by trialing them all) then knowledge of the process alone may not be sufficient to obtain…

> If you obtain two or more copies of the decrypted content you will be able to diff them and work out what you need to corrupt even without knowledge of the watermarking process.

By the time you've destroyed enough of the signal to remove the watermark, the content is unwatchable.

Re: How encryption for Cinema Movies works

#29

Post by tptacek »

codemiscreant wrote: post #24
john01dav wrote: post #3

Even with all of this onerous encryption and DRM, it's not hard to find pirated copies of movies. It makes me think that the sacrifice in ownership rights for the theaters over their equipment isn't worth it.

There is essentially zero piracy from these digital cinema releases. The pirate copies are generally from once it starts digitally streaming on one of the services including PPV, and when pirate copies exist earlier it is almost always someone with a camera in a theatre making a terrible quality screener. Piracy is inevitable, but in this case their model is much more robust that I would have predicted.

Most importantly, the industry concerns itself primarily with the new-release window; that high fidelity copies will eventually be widely available doesn't break the model.

Re: How encryption for Cinema Movies works

#30

Post by Aurornis »

dherls wrote: post #28

I'm confused why it's encrypted as a JPEG image per frame instead of one AES encrypted video file. Since the same AES key is used for each frame it wouldn't add any additional security imo

I think JPEG 2000 is simply the chosen format for distribution of the video, not for security.

JPEG 2000 has some interesting properties for very high quality video storage and transport where bandwidth is not a concern. The traditional encoded video formats we know are less preferred at this scale.

JPEG 2000 is resource intensive, though. The decoding hardware is probably either GPU based or using an FPGA implantation from one of the providers who makes hardware for this.

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