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!").
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!").