The GPU, not the TPM, is the root of hardware DRM • Hacker News Board

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

#221

Post by HeatrayEnjoyer » Thu, Jan 02, 2025, 2:58 PM UTC

kuschku wrote: post #85

jsheard wrote: post #55

Earlier quoted context omitted.

That only works with the weaker tiers of DRM which are typically only allowed to stream low resolutions. As mentioned in the OP article, the stronger DRM tiers never make the cleartext visible to software and those are mandatory for high quality streaming. Not to say the stronger tiers never get broken but it's a lot more involved than just recording them with OBS.

You can get HDMI capture cards that do 4K30 HDR while removing HDCP for $20. Use Microsoft edge for playback (so you get 4K HDR). Stylish as addon to remove any player hud. Especially useful if you want to legitimately use copyrighted content but obviously can't just use a pirated version.

Which cards strip modern HDCP?

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

#222

Post by wkat4242 » Thu, Jan 02, 2025, 2:59 PM UTC

sidewndr46 wrote: post #196

wkat4242 wrote: post #152

Earlier quoted context omitted.

> That's kind of the point. The vast majority of users aren't going to have their laptop stolen at all, if they do it will 99% of the time be by someone who only wants to wipe it and fence it, and attempts to access data are most likely to be by unsophisticated family members who would be defeated by a simple password without any TPM. True, any preboot password method (even fully software) will be sufficient to preve…

But it doesn't even do that. If I want to perform the "evil maid" attack why would I screw around with the bootloader? I'm just going to replace the entire device with something that captures the password & sends it to me remotely.

You could but the user might notice. Most business laptops don't exactly look like new.

I would very likely notice.

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

#223

Post by andrewaylett » Thu, Jan 02, 2025, 3:01 PM UTC

wkat4242 wrote: post #181

XorNot wrote: post #161

Earlier quoted context omitted.

No one wants a preboot password though. TPM means the system can boot and then do face login or whatever using the user's password in exactly one place. This is as much as most users will tolerate. And it also means Microsoft account recovery can work to unlock a forgotten password. The whole point is Microsoft don't want user devices to ever be trivially bypassed, regardless of how unlikely that is (probably more li…

Every phone has it these days. Doesn't seem to be a big deterrent? Laptops also need a password to log in. In fact in many cases a preboot password is safer. Because the comms between the TPM and the OS can often be sniffed. And if the TPM doesn't need validation because it hands off its keys, it can be bypassed that way. Again not really something that consumers have to worry about, but it's not quite difficult anym…

The phones are using their TPM equivalent to do it securely, though -- there's not nearly enough entropy in a lock screen to provide robust security, but the boot-time unlock depends on both the screen lock and the hardware, and the hardware will rate limit attempts to use it to turn lock screen inputs into usable encryption keys.

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

#224

Post by andrewaylett » Thu, Jan 02, 2025, 3:03 PM UTC

2OEH8eoCRo0 wrote: post #218

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…

I thought it was to DRM media?

As the article points out, the TPM is not in a good place, architecturally, to use for DRM: there's no path from the TPM to the screen that's not under OS (and thereby user) control.

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

#225

Post by teeray » Thu, Jan 02, 2025, 3:07 PM UTC

Wowfunhappy wrote: post #97

baby_souffle wrote: post #93

Earlier quoted context omitted.

> 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.

Likely not an issue. Convincing consumers to strap a brick to their face has proven to be a persistent challenge, which even Apple has not been able to overcome. However, there is also a nontrivial percentage of the population who medically cannot use VR/AR. This population is large enough that there is a market for "2D Glasses" for removing 3D effects from movies in cinemas. Releasing a title as a VR exclusive means excluding this population from your sales figures entirely.

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

#226

Post by db48x » Thu, Jan 02, 2025, 3:11 PM UTC

everdrive wrote: post #208

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…

I'm embarrassed to admit that I don't actually understand what a TPM does. My vague and probably incorrect impression is that it performs some sort of encrypted verification of firmware or hardware modules? Can anyone expand on what this does? My impression would be that this is not useful for most users, and would be much of a concern in industrial espionage situations. I have no confidence that I'm correct here.

It’s just a little cpu and some nonvolatile memory running a program. You can send it messages, and it will send back replies, but you cannot control which program is running on it. Of course this is vague enough that it could implement almost anything you want.

What makes it a TPM is the protocol it answers to. The TPM has a hardware RNG, and you can just ask it for some random numbers. That’s very simple. You can have it create encryption keys for you, since those are primarily just random numbers. You can ask it to _store_ a key for you, to be released to anyone who asks for it provided the TPM is in a certain state. What is this state? This is the really interesting part of the TPM.

The TPM has a number of registers that start off empty when the computer boots. At any point any program running on the computer can send a message to the TPM that asks it to incorporate an input into one of these registers. The input is a number, and the new value of the register is basically just the hash of the current value of the register and the new input.

If the BIOS/UEFI computes a hash of its own code plus the bootloader’s code and measures that into a register on the TPM then the bootloader could check the TPM to make sure that it hasn’t been tampered with before it boots. It’s easier though if the bootloader hashes the kernel (and the kernel command line) that it’s going to run and measures that into the same register. The kernel can then hash the initial ram disk and measure that in. At each step of the process we can measure the next important part of the OS and incorporate its value into the same register and at the very end we will have a number. If that number is the same every time we boot up the computer then we know that the computer and the software have not been tampered with. We can even send that number off over the network as part of a Remote Attestation protocol. You might have all the laptops you supply to your employees do this so that you can know that they haven’t been tampered with. Or all of your cloud instances could do this for the same reason. (Of course the exact number that the TPM ends up storing changes after every OS upgrade, and you need to have some way of knowing what numbers to expect, so this is a fair amount of work.) Remote Attestation is not really of any use to the average consumer, but reliably detecting a hacked OS would be.

Going back to encryption keys, you could store the encryption key for your home directory in the TPM, locked to a specific value of a specific register. You would then not be able to unlock your home directory if the computer has been tampered with. An attacker who boots off of a USB drive can’t possibly arrange for the same value to end up in the TPM, even assuming that they know what value is required. It will do them no good to take the encrypted disk out of the computer and put it in another one, because the key doesn’t go with it. Rubber hose cryptography isn’t useful either, even if there is also a password for your account. This should be quite valuable to many, if perhaps not all, users.

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

#227

Post by kccqzy » Thu, Jan 02, 2025, 3:14 PM UTC

no_time wrote: post #143

The author is correct in that media DRM is tied to GPU vendors on the field right now. But hardware backed DRM can be so much more invasive beyond that. I have no doubts the long term goal of MS is to have a Windows version of Play Integrity.[0] So total control over everything that happens on your device. Just to give an example of what could happen if this becomes reality: https://en.m.wikipedia.org/wiki/Web_Enviro…

I have trouble understanding your use of the term DRM. Media DRM makes sense: the copyright holders want to "manage" their rights digitally. How is that relevant to Play Integrity or WEI? Whose right is being protected or managed? If I have an Android without Play Integrity there are certain apps that will not run, but I don't see any rights being managed here: an app developer has the right to refuse service just like I have the right to refuse running an app.

In fact I see no relationship between DRM and Play Integrity other than a tenuous connection that both are about controlling what a user cannot do on their device. If this is what you mean, then you have made the same mistake as FSF by conflating unrelated technologies.

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

#228

Post by p0w3n3d » Thu, Jan 02, 2025, 3:16 PM UTC

snvzz wrote: post #183

CamperBob2 wrote: post #5

Earlier quoted context omitted.

DRM shouldn't be illegal, but works protected by DRM should be ineligible for copyright protection unless a key is placed in escrow somewhere. Basically, rightsholders should be be able to choose enforceable legal protection or unbreakable technological protection, but not both. Copyright was supposed to be a two-way street, but DRM permanently barricades one lane.

>should be be able to choose enforceable legal protection or unbreakable technological protection No. The latter would effectively mean rightsholders make their own laws, rather than follow the law. DRM should simply be abolished, as it interferes with the premise of copyright: To grow the public domain.

yeah, 105 years later we finally have a disney's a mickey mouse, but they still put the ears in every gadget to prolong it as a trademark.

TBH I can see now how the conglomerates created by buying smaller studios by big fish start owning everything. They've divided the market by themselves, and now they are rising their prices. Meanwhile I cannot make a screenshot of my favourite cartoon to create a meme, because of "copy protection". But I have right to do it you now? It's written in law in my country (Poland) that I can have small pieces recorded down, screenshotted etc, as long as I am doing some creative work on it, or just keep it to myself. THIS IS THE LAW HERE. And it's being ignored.

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

#229

Post by p0w3n3d » Thu, Jan 02, 2025, 3:18 PM UTC

anal_reactor wrote: post #163

Ah yes. DRM. 1. Companies offer service that people don't want to pay for, and blame piracy. 2. Someone realizes that they can eliminate piracy and make lots of money by offering good service. 3. Piracy slowly dies, because people prefer €5 monthly subscription over torrent. 4. Other companies catch up. The market gets fragmented. By the nature of the market, it becomes impossible for one company to offer clearly goo…

you've nailed it

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

#230

Post by alex7734 » Thu, Jan 02, 2025, 3:24 PM UTC

HeatrayEnjoyer wrote: post #212

botanical76 wrote: post #194

Earlier quoted context omitted.

There are cheats that give you more information than you should have. These typically require access to the game process's memory space. If you're cheating with a video capture card, this likely means you're allowing a program to rewrite your inputs to more accurately target player models. You will likely be banned if you do this on the same machine via screen capture. A video capture card can process the information…

Video capture cards can be countered with encrypted video from GPU to monitor. That's why you can't screencap 4k Disney+ movies.

Encrypted monitors can be countered by a high quality video camera mounted on a tripod behind your chair or on a wall or ceiling

Expensive, yes, but at that point you're already spending real money on a second computer with a GPU to do computer vision on the game video stream, so...