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Comment by chrisco255 | Hacker News Reader

> The resources needed to forge a signature aren't going to be much different than the resources needed to create a deepfake to begin with.

How? If you have a public/private key pair and then do some kind of multisig process wherein the manufacturer can sign the photo, the OS can sign the photo, and then a user supplied signature could also sign the photo. You're not going to be able to fake 3 cryptographic signatures without 3 private keys. It would be extremely difficult to fake all of that. It would take a concerted, concentrated effort and would be extremely rare in practice. It would certainly improve the situation.

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Once you compromise the device it doesn't matter how many keys there are because they all have to be on the device.

As a user, why does my private key need to be on the device? Especially, because I wouldn't want it there, because devices get stolen.

It has to be where the camera is. Otherwise the device holding your private key would need some way to authenticate photos from the device with the camera, which was the original problem.

First off, you'd have to steal the actual device. Then you'd have to break the device encryption itself to then extract a an encrypted version of a private key. (the private key itself can be encrypted with a password not stored on the device) You pair the 3 sigs plus a blockchain to track timestamps and photo hash signatures and maybe pair that with a different blockchain app to report lost or stolen devices...and you've got yourself as secure of a system as you can conceive in the age of deep fakes.

One threat is that a malicious actor uses a compromised device to fake a "legitimate" verified image.

This image can now be injected into the news cycle and be taken seriously.

Keeping a secret on the camera is more or less the "jailbreak problem", aka being able to make a dvd player or console that only does the things that the manufacturer wants.

I will be pretty sad if this problem is actually "solved" effectively because it portends a future where manufacturers can completely curtail user freedom. But...

If the key on the device is compromised by reverse engineering or because the manufacturer is compromised then the whole root of trust is gone.

Attackers can choose the weakest brand of camera.

You now have some doubt about any image that has been "verified" because it could have come from a compromised camera secret.

All the rest of the stuff, the blockchain, etc depends on the root of trust in the camera.

You also now have debates around camera country of origin because there is no near future world where governments can't lean on local manufacturers. Finally, doubt can be thrown on images retro-actively if we later learn that a camera we thought was secure, has vulnerabilities.

This isn't a "freedom" issue. And no, even if the private key on the device is hacked, you wouldn't be able to hack all the cameras (assuming the device manufacturer would embed a different key for each unit ID), you would still have to hack the OS and the User and the Phone's encryption. So the surface area of a hack would be small. You cannot fake all those signatures, you'd have to literally hack all that encryption.

All of this would be optional, of course. People can always edit out metadata. But it would lend credence and authority to a photograph or video. Which would carry more weight in a court of law, for example, where this stuff really matters.

This is an interesting conversation because we both seem convinced we're "obviously right". I am clearly having trouble understanding your point of view. I apologise in advance if I'm mis-understanding your argument. Perhaps "First off, you'd have to steal the actual device" from upthread is the clue.

I think the disconnect might be that you are working from a threat model where someone else is trying to tamper with an image from your camera. I agree you could make that arbitrarily difficult. But I am primarily concerned with the threat where someone is tampering with their own camera to fake evidence. This possibility makes it harder for you to prove that your own image is legitimate.

Your reasoning implies that one or two hacked cameras are not a problem. To my way of thinking, the possibility that "at least 1 hacked camera exists" or "any camera could possibly be hacked" are enough to throw doubt on any "verified" images that someone tries to present in a high stakes context such as national security or the courtroom. We're back to debating provenance.

I don't know. I don't want to live in a world where someone can literally murder someone on camera and get away with it on a technicality. Witness testimony is already used in court and is quite unverifiable and subject to all sorts of psychological phenomenon where people sometimes believe they saw something entirely different than what actually happened. I think cryptographic signatures couldn't guarantee validity 100%, but they could improve the situation in a world of deep fakes on demand.

It would require a larger degree of premeditation and effort to convincingly pull off a deep fake in that world.

> a technicality

It's not a technicality if the video can't be distinguished from perfect nonsense. Just as you don't let someone with a documented history of hallucinations testify on their own.

You'd make the camera reach out to a signing server for the user's signature. You'd even sign the whole photo, not a hash supplied by the camera, to give you (via the server) a chance to verify the image was correct.

Or, you'd adapt a hardware wallet to do the same. Either way, there'd be two devices from two manufacturers, communicating over a transparent protocol.

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