If C2PA and similar signature systems ever become a meaningful authenticity signal, they will create huge incentives for someone (potentially a state actor) to hack at least one camera in order to sign images of arbitrary provenance with its private keys. This will in turn inevitably lead to the same game of cat-and-mouse we have seen play out with video DRM schemes, where keys are regularly extracted from exploitable devices and used to decrypt as much content as possible before the device gets blacklisted entirely (harming all legitimate owners in the process).

I don't think that that's a good idea, because it implies trust when there actually isn't any.

Being signed with something just means that whoever has that key could've done that. That might be the owner of a specific camera, but it might also be the camera manufacturer, anyone else in the supply chain, or anyone who dumped the key.

Imagine fake evidence signed with the same key as your camera uses being used in court against you. And the court believes it because it has this signature attached and those computers are very secure and all.

Exactly that will happen. Not widespread, of course, but it will.

The hard part is deciding how much post processing is acceptable with these images. Feels like a lot of phone cameras optimize images and curious how much of it is considered “AI”

And then some incriminating photo is made with your forged signature. "Not like that, not like that!"

What would prevent someone from applying the same algorithm on a computer to sign arbitrary images?

How exactly would this work?

People take RAW photos. Load it up in a RAW editing tool. Manipulate it. Then load it in Gimp. Manipulate some more.

Will the final result have the signature?

And if it does, what use would it be?

When I was in photography class in college, I created backplates in photoshop for still life portraits of small trinkets I was photographing. The photos were taken on black and white film and developed in the campus dark room. Led to some impressive photos. In our class's critiques, I explained how it was done. A lot of peers went from impressed to meh'd. The point: the black and white film laundered the new-age manipulation, and a digitally signed photo from a modern camera remains vulnerable to the same premise.

> You could prove the photo was real.

No. You'd only ever be able to show that key material belonging to $specific_camera was used to sign/mark the image.

Was the camera manufacturer breached? Did somebody on the factory floor steal some keys during the provisioning step? Or did somebody build their own photo-sensor simulator and plug _that_ in to the camera's motherboard to feed it a "real" image? Before going _that_ far, just point the unmodified camera at a sufficiently high resolution display...

do you believe this should be mandated by regulation, or voluntarily offered by manufacturers as a value-add feature? ("all" implies the former.)

"I think it would be nice if all pens added a unique isotopic tracer signature to their ink. You could tell exactly who wrote everything."

"I think it would be nice if all typewriters had their unique fine-detail type artifacts registered with the government. You could tell exactly who authored a given document."

I think it would be nice if you took these ideas back to Stalinist Russia where they belong.