Hacker News Reader

Comment by initplus | Hacker News Reader

This is a misguided attempt that will fail - all signing the image in camera does is verify that those pixels were sent by the camera sensor.

It’s trivial to work around this and create inauthentic signed images by staging a fake scene, or doctoring an image and then feeding the doctored image into the camera sensor.

For more details see https://www.hackerfactor.com/blog/index.php?/archives/919-Cl...

View on HN

Fake scenes and misplaced cameras are old problems that we already have some solutions for. Since the idea here is to solve the separate and new problem of deepfakes, I don't think this criticism makes a strong case against digital signatures in photography.

It adds a layer of difficulty for fakery. At the very least, such a signed image is a better "source" of truth than an unsigned jpeg from Telegram. We will enter and perhaps are already in an era where you need to build a habit of verifying photographs that proclaim some form of truth.

> It’s trivial to work around this and create inauthentic signed images by staging a fake scene

I'm not sure what the implication of this is. Reuters is attempting a basic technological solution to a technological problems (images can be duplicated, altered and reshared by non-Reuters parties for malicious purposes).

Someone staging a fake scene is not a technological problem that can be solved (though I imagine some amount of depth information and geo-data in the image would help)

Unfortunately, you don't need a fabricated scenario to convince people to believe the opposite of what is true. Media outlets routinely select which facts to report, influencing public perception. While technical professionals are often meticulous in verifying the accuracy of information, even they can't employ Bayesian methods to arrive at the truth if the evidence presented to them is already filtered.

That would require a conspiracy by someone with physical access to the camera. Spoofing the GPS would require even more elaborate techniques. At a minimum if you trust Reuters and their camera people, you know the images taken were taken by them in their custody at those locations. That’s a lot more than we have now.

That's already what we have now. Reuters stakes their credibility on this. They just don't have any.

> Spoofing the GPS

You can already do it now. Somebody even sells premade ones because some people what to screw up Pokemon go players. And it even already caused safety problems. It's the easiest thing of the whole part. Modifying camera require skills. Spoofing gps can be done with a gps spoofer that you may be able to buy somewhere.

If only GPS signals were cryptographically signed

Cryptographically signing GPS signals makes it harder to spoof GPS coordinates but does not stop it completely.

A spoofer could obtain signed GPS signals from the time and location where they are claiming to have taken a photo and combine them with a photo taken in a different time and place.

I was thinking that if secure timestamping could be done quickly enough, it might be possible to both bound the event by the future-light-cones of the spacetime points the GPS satellites sent the signed signal, and the past-light-cones of the timestamping event, but I suppose that’s probably not feasible (even with signed GPS signals).

Now, maybe on an interplanetary scale (with various sources playing the role of the GPS satellites, and various locations doing secure timestamping) it could be enough in order to be able to establish (beyond plausible hope of spoofing) a kind of rough region in space-time, but, maybe not very precise.

But any trickery employed is traceable back to that specific camera, meaning that the camera owner's reputation is on the line if it's discovered.

Will that reputational risk actually have any teeth? That's up to us (society at large).

Yeah, couldn’t you simply rephotograph a doctored image off a sufficiently high-res monitor?

You could, but if you got busted doing that, your reputation would take a hit. Everyone would know it was you because you own the camera with that private key. (To wriggle out of it, you would need to claim that either your camera was stolen before the photo was taken, or that Canon/Reuters's private key was compromised. The former claim would be harder if there was, e.g., a second digital signature stored in the JPEG showing that you confirmed your identity with a fingerprint 10 minutes earlier.)

Also: Could you, actually? Maybe photos of monitors have "tells" that can be detected with some kind of image processing.

In the end it is not too different from the current solution. If Reuters, or a specific photographer, published manipulated images their reputation also takes a hit. There is a wikipedia article and people know it was you.

you can prevent feeding the doctored image into the sensor if the camera also senses depth, and only signs the image and depth information together. this is how they prevent a photo from unlocking face id on a phone

Agreed, it's no better than using a fingerprint to secure a device.

Seems harder then using photoshop or AI.

Reply on news.ycombinator.com