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The GPU, not the TPM, is the root of hardware DRM

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Re: The GPU, not the TPM, is the root of hardware DRM

#91

Post by bri3d »

mjg59 wrote: post #23
zb3 wrote: post #15

> GPU vendors have quietly deployed all of this technology Citation or technical details needed. Obviously it "makes sense" that for 4K HD content you "probably" want to offload the decoding into the GPU, but this is the first time I see this mentioned and there are no links to technical details. In contrast, TEE / TrustZone and even the recent AVF with pVM - these are well documented technologies.

The Playready docs make it clear the implementation is either in TEE or implemented in GPU hardware, and x86 has no TEE, so. You can easily find driver changelogs describing it being enabled for different hardware generations.

> x86 has no TEE

Not really; AMD have PSP (which, okay, isn’t x86, but it’s on the die) and Intel, as you mention in your post, had SGX and have ME. Google use PSP TrustZone to run Widevine on Chromebooks, for example. PowerDVD used SGX to decrypt BluRay, which led to BluRay 4K content keys being extracted via the sgx.fail exploit.

You’re right though that PlayReady is usually GPU based on x86; on AMD GPUs PlayReady runs in GPU PSP TrustZone. On Intel iGPUs I think it runs in ME.

The lower-trust (1080p only) software version of PlayReady uses WarBird (Microsoft’s obfuscating compiler) but this is of course fundamentally weak and definitely bypassed.

Anyway, none of this takes away from your post, which I agree with. The FSF (and many HN commenters) have been whining about TPM in unfounded ways since the 2000s.

Re: The GPU, not the TPM, is the root of hardware DRM

#92

Post by Rohansi »

osy wrote: post #26

> I'm going to be honest here and say that I don't know what Microsoft's actual motivation for requiring a TPM in Windows 11 is. It is quite obvious: to force people to buy a new PC. TPM provides no added security value for the vast majority of users[1] but it is a convenient hardware that has only started to become standard (fTPM) in PCs built in the last ~8 years so it provides an excuse for Microsoft to declare co…

Requiring TPM can actually benefit multiplayer video games because it introduces a secure way to identify hardware being used by cheaters. Right now everything being used by games is easily spoofed by cheats so cheaters just need to get a new account to continue cheating after being banned.

Re: The GPU, not the TPM, is the root of hardware DRM

#93

Post by baby_souffle »

tasn wrote: post #20
jakogut wrote: post #12

Earlier quoted context omitted.

There's always an analog loophole. Even if the OS is unable to access the memory storing the decrypted data, you could always just plug the output of the machine into a capture card and capture the decrypted stream that way. I suppose some monitors and TVs have "features" to cryptographically handshake with the GPU and ensure a secure link, but at some point the data must be decrypted and decoded to be displayed. Thi…

The end goal is DRM all the way to the screen. No capture cards will be allowed. It's a cat and mouse game, but I wouldn't discount these efforts as a mere speed bump. Screen enforced DRM will make things much harder. A motivated individual with the right tools and hardware hacking know how may be able to jailbreak a screen to record stuff, but that's going to make things out of reach for most people.

> The end goal is DRM all the way to the screen. No capture cards will be allowed.

Sure, but the closer you get to the eye ball, the bigger the loophole is.

It's not common anymore, but _way_ back in the day, some releases were made *in the projection booth* with a semi-pro camera on a tripod pointed at the screen. (look for old NFO files with `TS` or `TeleSync` in them to get an idea of when this was common-ish)

The analogue loophole will remain open until there's a HDMI to optical nerve technology that we're all forced to get at birth.

Re: The GPU, not the TPM, is the root of hardware DRM

#94

Post by jsheard »

Retr0id wrote: post #65
lksaar wrote: post #54

Earlier quoted context omitted.

WV L1 Keys/ PR SL 3000 keys require breaking into the TEE to steal those decryption keys. Ever wondered why netflix 4k web-dls take a while for less popular shows? Netfliy monitors these more tightly apparently and blacklist keys that are used to download. Then the group needs to buy some new device, the old one is burned.

It's true that known-compromised keys get revoked, but it's possible to avoid them knowing you've compromised a particular device.

I think there's some kind of watermarking going on, so once a rip is released to the public they can trace it back to which device keys were used to decrypt it.

Re: The GPU, not the TPM, is the root of hardware DRM

#95

Post by ntqvm »

The author seems misinformed about the purpose of TPM to DRM schemes.

The purpose of a TPM, in this case, is not to provide encryption, but instead to provide so-called ‘authenticity’. A TPM with its attestation capabilities can allow a remote validator to attest the operating system and system software you are running via the PCRs which are configured based on it, with Secure Boot preventing tampering. [1] Google tried to implement APIs to plug this into the Chrome browser, which was later abandoned after backlash. [2]

In this case, the TPM can allow services like Netflix or Hulu to validate the hardware and software you are currently running, which provides the base for a hardware DRM implementation as stated in the article. Don’t be surprised if your non-standard OS isn’t allowed to play back content due to its remote validation failing if this is implemented.

TPMs also have a unique, cryptographically verifiable identifier that is burnt into the chip and can be read from software. This allows for essentially a unique ID for each computer that is not able to be forged, as it is signed by the TPM manufacturer (in most cases Intel/AMD as TPMs on consumer hardware are usually emulated on the CPUs TEE). If you were around for the Pentium III serial controversy, this is a very similar issue. It's already used as the primary method of banning users on certain online video games, but I wouldn’t be surprised to see it expand to services requiring it to prove you aren’t a “bot” or similar if it gets wider adoption.

There is a great article going more into detail about the implications of TPM to privacy from several years ago, which was the basis for this reply. [3]

[1]: https://github.com/MicrosoftDocs/azure-docs/blob/main/articl...

[2]: https://github.com/explainers-by-googlers/Web-Environment-In...

[3]: https://secret.club/2021/06/28/windows11-tpms.html

Re: The GPU, not the TPM, is the root of hardware DRM

#96

Post by Retr0id »

jsheard wrote: post #94
Retr0id wrote: post #65

Earlier quoted context omitted.

It's true that known-compromised keys get revoked, but it's possible to avoid them knowing you've compromised a particular device.

I think there's some kind of watermarking going on, so once a rip is released to the public they can trace it back to which device keys were used to decrypt it.

Watermarking would require a separate version of each encoded file for each target device, which is not amenable to efficient CDN-ing.

It's quite easy to grab the encrypted media files, as they go over the wire - do this from two devices and compare what you get. (you don't need to strip the DRM to see if the two files are identical)

Re: The GPU, not the TPM, is the root of hardware DRM

#97

Post by Wowfunhappy »

baby_souffle wrote: post #93
tasn wrote: post #20

Earlier quoted context omitted.

The end goal is DRM all the way to the screen. No capture cards will be allowed. It's a cat and mouse game, but I wouldn't discount these efforts as a mere speed bump. Screen enforced DRM will make things much harder. A motivated individual with the right tools and hardware hacking know how may be able to jailbreak a screen to record stuff, but that's going to make things out of reach for most people.

> The end goal is DRM all the way to the screen. No capture cards will be allowed. Sure, but the closer you get to the eye ball, the bigger the loophole is. It's not common anymore, but _way_ back in the day, some releases were made *in the projection booth* with a semi-pro camera on a tripod pointed at the screen. (look for old NFO files with `TS` or `TeleSync` in them to get an idea of when this was common-ish) The…

> The analogue loophole will remain open until there's a HDMI to optical nerve technology that we're all forced to get at birth.

This is kind of a pointless tangent, but you might not have to go that far. It's probably hard to get a recording of the Apple Vision Pro for instance.

Re: The GPU, not the TPM, is the root of hardware DRM

#98

Post by jdietrich »

geerlingguy wrote: post #29
tasn wrote: post #20

Earlier quoted context omitted.

The end goal is DRM all the way to the screen. No capture cards will be allowed. It's a cat and mouse game, but I wouldn't discount these efforts as a mere speed bump. Screen enforced DRM will make things much harder. A motivated individual with the right tools and hardware hacking know how may be able to jailbreak a screen to record stuff, but that's going to make things out of reach for most people.

With how good modern screens are, and how good cameras are (and how easy both are to hack), you could always play back the video and capture the photons through the air. There was something called Macrovision back in the VHS/DVD days that tried to defeat digital/analog conversion, and I'm sure visual techniques could be devised... But I imagine someone with a good OLED and a good mirrorless camera (or even a cell pho…

Once upon a time, this was how all video-to-film transfers worked.

https://en.m.wikipedia.org/wiki/Kinescope

Re: The GPU, not the TPM, is the root of hardware DRM

#99

Post by __MatrixMan__ »

Rohansi wrote: post #92
osy wrote: post #26

> I'm going to be honest here and say that I don't know what Microsoft's actual motivation for requiring a TPM in Windows 11 is. It is quite obvious: to force people to buy a new PC. TPM provides no added security value for the vast majority of users[1] but it is a convenient hardware that has only started to become standard (fTPM) in PCs built in the last ~8 years so it provides an excuse for Microsoft to declare co…

Requiring TPM can actually benefit multiplayer video games because it introduces a secure way to identify hardware being used by cheaters. Right now everything being used by games is easily spoofed by cheats so cheaters just need to get a new account to continue cheating after being banned.

Anti-cheat is a lousy cover for something that's going to be much more lucrative when used to correlate the accounts of journalists and whistleblowers such that they can be silenced. It's censorship tech.

Re: The GPU, not the TPM, is the root of hardware DRM

#100

Post by jsheard »

Retr0id wrote: post #96
jsheard wrote: post #94

Earlier quoted context omitted.

I think there's some kind of watermarking going on, so once a rip is released to the public they can trace it back to which device keys were used to decrypt it.

Watermarking would require a separate version of each encoded file for each target device, which is not amenable to efficient CDN-ing. It's quite easy to grab the encrypted media files, as they go over the wire - do this from two devices and compare what you get. (you don't need to strip the DRM to see if the two files are identical)

They wouldn't necessarily need to serve different data to each client when they control the whole playback stack, they could get clever by including duplicate frame data with subtle differences and making each device key only able to decrypt one of the variants. Repeat that throughout a show to add additional bits to the signature until it's uniquely identifiable.
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