Earlier quoted context omitted.
Digital signatures on photos, with each camera certificate signed by the manufacturer. Not sure why they don't do it at scale yet.
And then comes Google Photos and applies a filter, goodbye signature (in this case, the phone's). Or I have an old-fashioned film camera... I guess this idea would work only with DSLRs, which aren't that popular anymore nowadays thus we won't solve that much of the original problem.
If a digital signature would stay valid after retouching, there's no value in having it in the first place. If the picture would be re-signed on editing, what's the purpose of that signature...?