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Trying to extract Widewine key: A journey to failure

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Re: Trying to extract Widewine key: A journey to failure

#51

Post by conradev »

wmf wrote: post #47
grishka wrote: post #44

Earlier quoted context omitted.

DRM is always pointless because the content has to be converted to analog form at some point. So, it gets decrypted in the DistrustZone, decompressed, then encrypted again before it goes over HDCP to your display, which then decrypts it to show it on the screen. Couldn't you capture the LVDS signal that the display panel receives? And even if you don't do that, isn't every version of HDCP cracked already so you could…

The last bastion of DRM is forensic watermarking (so they can trace the leaked video back to your device) and key revocation (so your device won't play any new content). These techniques are so complex that they aren't used much.

Isn't it also incompatible with the distribution model? Because personalizing video for every customer is hard to scale for companies that rely on reducing cloud costs

Re: Trying to extract Widewine key: A journey to failure

#52

Post by wmf »

grishka wrote: post #50
wmf wrote: post #47

Earlier quoted context omitted.

The last bastion of DRM is forensic watermarking (so they can trace the leaked video back to your device) and key revocation (so your device won't play any new content). These techniques are so complex that they aren't used much.

So they trace the ripped video file to a particular throwaway account that was registered with a prepaid card, then what? And if you're determined enough, you could as well rip multiple copies on behalf of multiple accounts and average out the pixel colors.

The idea is to revoke the device, not the account.

Re: Trying to extract Widewine key: A journey to failure

#53

Post by throwaway525142 »

grishka wrote: post #50
wmf wrote: post #47

Earlier quoted context omitted.

The last bastion of DRM is forensic watermarking (so they can trace the leaked video back to your device) and key revocation (so your device won't play any new content). These techniques are so complex that they aren't used much.

So they trace the ripped video file to a particular throwaway account that was registered with a prepaid card, then what? And if you're determined enough, you could as well rip multiple copies on behalf of multiple accounts and average out the pixel colors.

> you could as well rip multiple copies on behalf of multiple accounts and average out the pixel colors.

Can you show that this can reliable get rid of the fingerprinting? This particular method could be countered by only including the fingerprint info in a few random frames, then you'd be able to retrieve the account info of all the accounts that participated in ripping. I don't think finding a method to counter any sort of fingerprinting is as easy as "just averaging the pixels".

Re: Trying to extract Widewine key: A journey to failure

#54

Post by wmf »

conradev wrote: post #51
wmf wrote: post #47

Earlier quoted context omitted.

The last bastion of DRM is forensic watermarking (so they can trace the leaked video back to your device) and key revocation (so your device won't play any new content). These techniques are so complex that they aren't used much.

Isn't it also incompatible with the distribution model? Because personalizing video for every customer is hard to scale for companies that rely on reducing cloud costs

The watermarking is done during playback, not distribution.

Re: Trying to extract Widewine key: A journey to failure

#55

Post by jshwlkr »

azalemeth wrote: post #11

From the repo: >It is my honest opinion that DRM is a malignant tumor growing upon various forms of media, and that people that either implement or enforce implementation are morally repugnant and do no good to society. With that in mind, I was sad to learn in May 2021 that the original extension would soon be rendered obsolete. I really can't agree more. I don't use, and never have, services that require DRM. I buy…

I believe you meant https://www.hyperion-records.co.uk/

Re: Trying to extract Widewine key: A journey to failure

#56

Post by azalemeth »

jshwlkr wrote: post #55
azalemeth wrote: post #11

From the repo: >It is my honest opinion that DRM is a malignant tumor growing upon various forms of media, and that people that either implement or enforce implementation are morally repugnant and do no good to society. With that in mind, I was sad to learn in May 2021 that the original extension would soon be rendered obsolete. I really can't agree more. I don't use, and never have, services that require DRM. I buy…

I believe you meant https://www.hyperion-records.co.uk/

I did -- thank you and apologies for getting it wrong.

Re: Trying to extract Widewine key: A journey to failure

#57

Post by azalemeth »

throwaway525142 wrote: post #53
grishka wrote: post #50

Earlier quoted context omitted.

So they trace the ripped video file to a particular throwaway account that was registered with a prepaid card, then what? And if you're determined enough, you could as well rip multiple copies on behalf of multiple accounts and average out the pixel colors.

> you could as well rip multiple copies on behalf of multiple accounts and average out the pixel colors. Can you show that this can reliable get rid of the fingerprinting? This particular method could be countered by only including the fingerprint info in a few random frames, then you'd be able to retrieve the account info of all the accounts that participated in ripping. I don't think finding a method to counter any…

It's my understanding that most schemes actually use very low frequency encoding with a large amount of error robustness built in (probably involving Haar wavelets) in order to maximize the probability that it survives re-encoding. Still, these schemes are not faultless: if you have two devices, and are knowledgeable enough to break the DRM twice for the same content, you're probably smart enough to take the md5 and shasum of the resulting bitstreams and diff them. Any discrepancy results in signal processing transforms until they have the same hashes...

Re: Trying to extract Widewine key: A journey to failure

#58

Post by sblom »

wmf wrote: post #54
conradev wrote: post #51

Earlier quoted context omitted.

Isn't it also incompatible with the distribution model? Because personalizing video for every customer is hard to scale for companies that rely on reducing cloud costs

The watermarking is done during playback, not distribution.

I took conradev to mean "the model of distributing the same content to everyone via traditional (passive) CDN".

Movie theater watermarking is done during playback, but if Netflix was going to do watermarking, it would have to be done prior to delivery of streamed bits or it would be susceptible to the same "it's just software" attacks as any other local software-only approach to DRM.

Re: Trying to extract Widewine key: A journey to failure

#60

Post by wmf »

sblom wrote: post #58
wmf wrote: post #54

Earlier quoted context omitted.

The watermarking is done during playback, not distribution.

I took conradev to mean "the model of distributing the same content to everyone via traditional (passive) CDN". Movie theater watermarking is done during playback, but if Netflix was going to do watermarking, it would have to be done prior to delivery of streamed bits or it would be susceptible to the same "it's just software" attacks as any other local software-only approach to DRM.

Is Widevine L1 "just software"? If its key distribution can somehow remain uncracked for years then maybe it could also do client-side watermarking.
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