Trying to extract Widewine key: A journey to failure • Hacker News Board

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

#81

Post by Godel_unicode » Mon, Aug 02, 2021, 1:38 AM UTC

matheusmoreira wrote: post #72

beefjerkins wrote: post #71

Earlier quoted context omitted.

I agree that our current copyright system is certainly out of hand, but it does serve a purpose. Out of curiosity, what system would you suggest in its stead?

Maybe patronage schemes? Crowdfunding? I have no idea. I just know that we can't go on like this. The only way to enforce copyright in the 21st century is to destroy computing freedom. I'd rather sacrifice the entire copyright industry than have computers that only run software they approve.

Except that's not true. There is tons of copywritten work sold online without DRM. It's just a matter of getting the business model right.

https://www.amazon.com/gp/feature.html?ie=UTF8&docId=1000265...

> every song from Amazon MP3 is DRM-free and encoded in high-quality 256-kbps MP3 format. This means that they will play on any MP3 player, so you don't need to worry about file format compatibility or licenses that expire.

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

#82

Post by mjevans » Mon, Aug 02, 2021, 1:39 AM UTC

azalemeth wrote: post #57

throwaway525142 wrote: post #53

Earlier quoted context omitted.

> 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…

You'd ideally do this for 3+ devices and just majority vote on every framelocked frame; take the mean average if there isn't a median.

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

#83

Post by elcritch » Mon, Aug 02, 2021, 1:39 AM UTC

SilverRed wrote: post #64

elcritch wrote: post #46

Earlier quoted context omitted.

In theory DRM could be mathematically perfect. However DRM relies on actual implementations both in software and hardware and shares a lot with broader security. Software implementations can have bugs but it’s relatively easy to ship fixes. The hardware level however is where it becomes very difficult to ensure a valid implementation of “secure compute” or “trusted zones” which are key to DRM and general security, pa…

How can DRM ever be perfect? It relies on your computer to be able to decrypt the data so it an never be "mathematically perfect" like regular encryption can be. Current DRM is all about shoving the decryption part as deep in to a chip as possible and betting on the fact that it is physically too hard to extract that info. So it will always be exploitable with some amount of effort.

The DRM implementation and algorithm could be "perfect" in a mathematical sense, but as you point out they tend to rely on a PUF in the silicon hardware. Currently very hard to extract but not completely so. However, say a system had a quantum based PUF then it could be unclonable due to QM. Such a system could still be potentially cracked by causing issues in the processor itself like with the ESP32s. Which was my point, since there's a physical system to work in it'd be impossible in a practice to make perfect. Hence it boils down to economics.

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

#84

Post by denkmoon » Mon, Aug 02, 2021, 1:42 AM UTC

step21 wrote: post #14

baybal2 wrote: post #5

Earlier quoted context omitted.

The point of semi-unusable DRMed crap when L1 released keep getting WEB-DLed? Very likely it's not the Shield now which leaks L1, but an actual key recovery because they get the stream even before it gets watermarked in the secure domain. My guess, it's Qualcomm's debugging TZ applets. They cannot really revoke keys because they will take down a giant amount of Snapdragon based handsets for which manufacturers don't…

What's L1? web-dls I have seen are always relatively low resolution, so at least it protects fullhd or 4k.

The Grand Tour S04E03 4k web-dl is readily available on private torrent trackers hours after public release on Amazon Prime.

No idea what encryption Amazon use, but suffice to say it is thoroughly broken by someone out there. Given the expense of acquiring those presenters and the production costs of their shows, and how they bring people to the Prime video platform, I suspect Amazon is reasonably interested in keeping that content protected.

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

#85

Post by bottled_poe » Mon, Aug 02, 2021, 1:49 AM UTC

siliconc0w wrote: post #19

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…

"because DRM is fundamentally pointless" I dunno, it gave this person a lot of trouble and the result is maybe a very narrow victory that doesn't practically matter? And this is the lowest level of widevine security - L3 which is basically assumed to be owned. Good luck with L1 which uses trusted compute primitives. DRM has won. And I'm saying this as someone who agrees DRM is a threat to society as we're taking thin…

> DRM is a threat to society as we're taking things that the world could otherwise have for free

But someone needs to pay to create those things in the first place. Payment for work after the fact is the basic incentive.

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

#86

Post by rodgerd » Mon, Aug 02, 2021, 1:52 AM UTC

nyuszika7h wrote: post #22

magila wrote: post #20

Earlier quoted context omitted.

If you know where to look L1 content can be readily downloaded, including the original 4K streams. As usual the net effect of DRM is to make the paid service inferior to piracy. That's not what I would call "wining".

I don't know why you're being downvoted, you're right. There are plenty of TrustZone exploits that allow extraction of L1 keys.

Pay NZ$20/mo for Netflix in UHD, or fuck around on pirate sites to make sure none of the people making the series and films I'm enjoying, while hoping that no-one has dropped an entertaining payload in the site ads or the files I'm downloading is "piracy is more convenient"?

The downvotes are for a shit take disconnected from the reality of people who aren't determined not to pay for something.

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

#87

Post by Godel_unicode » Mon, Aug 02, 2021, 1:55 AM UTC

bawolff wrote: post #29

From the repo > In the end, I only extracted about half of the RSA key. Not a cryptographer, but i thought half the rsa key was all you needed with coopersmith's attack.

Although I too am no cryptographer, I believe there is an additional constraint where the public exponent needs to be small. Also the paper I read says these conditions can lead to discovery of the key in "polynomial time" which doesn't necessarily mean fast.

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

#88

Post by Arainach » Mon, Aug 02, 2021, 1:57 AM UTC

siliconc0w wrote: post #19

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…

"because DRM is fundamentally pointless" I dunno, it gave this person a lot of trouble and the result is maybe a very narrow victory that doesn't practically matter? And this is the lowest level of widevine security - L3 which is basically assumed to be owned. Good luck with L1 which uses trusted compute primitives. DRM has won. And I'm saying this as someone who agrees DRM is a threat to society as we're taking thin…

>we're taking things that the world could otherwise have for free and denying it them so we can instead charge a small % for it

Are we? Where are the studios making feature-length movie-quality content and putting it on YouTube to be supported by ad money? There isn't even an equivalent to TV in that form factor. All of the new content that requires any sort of production budget (actor salaries, non-trivial special effects) is on platforms with subscription fees and DRM to require those subscription fees because we can't have these things for free.

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

#89

Post by [deleted] » Mon, Aug 02, 2021, 1:59 AM UTC

vladvasiliu wrote: post #42

wmf wrote: post #39

Earlier quoted context omitted.

Between the video decoder and the screen is the display server (e.g. Xorg or GNOME Shell) which is untrusted.

This wasn't my understanding. If the decoding happens in hardware, I wouldn't have expected the decoded video to be passed back to the display server to be sent back again to the GPU and out to the screen. My understanding was that there was some kind of compositing going on, in hardware, where the display server would tell the GPU to display the output between some coordinates, but the server itself wouldn't know wh…

[deleted]

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

#90

Post by Arainach » Mon, Aug 02, 2021, 2:04 AM UTC

Godel_unicode wrote: post #81

matheusmoreira wrote: post #72

Earlier quoted context omitted.

Maybe patronage schemes? Crowdfunding? I have no idea. I just know that we can't go on like this. The only way to enforce copyright in the 21st century is to destroy computing freedom. I'd rather sacrifice the entire copyright industry than have computers that only run software they approve.

Except that's not true. There is tons of copywritten work sold online without DRM. It's just a matter of getting the business model right. https://www.amazon.com/gp/feature.html?ie=UTF8&docId=1000265... > every song from Amazon MP3 is DRM-free and encoded in high-quality 256-kbps MP3 format. This means that they will play on any MP3 player, so you don't need to worry about file format compatibility or licenses that e…

The production costs in music are orders of magnitude lower than those for video. It takes far fewer people far fewer days to record a song than a TV show or a movie. The equipment involved in recording, mixing, and special effects are all dramatically cheaper, which also makes the entire process more accessible and enables scales that do not exist for most media.

A business model for one thing does not generalize.