The problem is how to do you make that signature or digital artifact accessible by the general public.
Any visual artifact can be mocked, so we end up with the same problem as clickbait titles, where the conclusion one arrives at from just a title can be disproved, but it doesn't prevent the false information from going viral.
What good is it to say "that video you saw was fake!" after the video has spread around and done the damage already?
It's hard to come up with a solution to this problem just because the solution has to preempt the problem. A cryptographic visual artifact _could_ work, but it's still likely that misinformation via deep-fakes will cause problems for society at large.
Yeah agreed — making security & authenticity understandable to a layperson is always going to be tricky.
Websites like Twitter adopting a "blue tick" for a validated profile on their platform though is a model people seem to get. If we had some equivalent of a "blue tick" at a user-agent level, e.g. a for your browser to take a signature and display it in a standardised, human way to say "this video is signed by bbc.co.uk" it could work. (With a similar model for user-agents elsewhere e.g. you'd probably need adoption in apps like WhatsApp to get traction.)
The other side of it (like privacy discussions) is how much the average person will care — tabloid journalism often skirt the borders of what they can get away with at the moment & they nominally have a duty currently to only write factual information. If Fox News or the Daily Mail release videos and put their own signature to it, then you arguably lend them legitimacy ("it's on the news so it must be true. It's signed by them and all!").
Any visual artifact can be mocked, so we end up with the same problem as clickbait titles, where the conclusion one arrives at from just a title can be disproved, but it doesn't prevent the false information from going viral.
What good is it to say "that video you saw was fake!" after the video has spread around and done the damage already?
It's hard to come up with a solution to this problem just because the solution has to preempt the problem. A cryptographic visual artifact _could_ work, but it's still likely that misinformation via deep-fakes will cause problems for society at large.