The idea is to be able to prove that a photo you took was captured by a camera, not generated. That would be helpful in the context of a disputed news story, a court case, etc.

Would that ever be relevant for a screenshot?

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qingcharles 2 hours ago | parent | next [-]

It's not massively helpful for a court case, IMO. This has been handled the same way since the invention of photography: ask the photographer to swear under oath they took the photo. (technically, laying a foundation for the evidence)

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ranger_danger 5 hours ago | parent | prev [-]

Yes in multiple ways, and there's probably more than this:

It's relevant that a screenshot doesn't have a signature, in the case that you want to remove any "proof" or tracking info from a real photo when uploading an image. Maybe I don't want people to know what brand/model of camera I use.

And it's relevant if a screenshot did have a signature if you want to "prove" that the screenshot itself hasn't been tampered with after the fact.

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xg15 2 hours ago | parent [-]

In the method proposed in the paper, the signature is stored in the pixels and ostensibly even survives some compression. So if you made a screenshot of a signed image, the image would still have its signature inside the screenshot, but the screenshot wouldn't have any (new) signature as a whole.

That's how I understood it at least.

	▲	ranger_danger an hour ago \| parent [-]
		I would assume you could make big enough differences in color/contrast/brightness and especially 3D rotation (similar to taking a photo of a screen) would make such a signature unreadable... but I would love to be proven wrong.