Would work in some but not all scenarios. Perhaps the video is legitimate but embarrassing for the represented party, so the represented party declines to sign it.
A. Video/audio/text of/by person, signed, we have knowledge that this video bears their signature, they endorse it
B. Unsigned
B1. Unsigned because it's not them
B2. Unsigned because they don't want it to be associated with them
I think this is still a better state of affairs because we can verify positive endorsements as genuine or not.
You're right, we couldn't verify stuff they refused to sign, but!
Imagine the state coerces people to carry small devices with radio transmitters that constantly transmit, over the length of a second, a signed key, ad infinitum; that way no one can plausibly deny that it wasn't them (unless someone plants the persons device on an imposter).
If I have some embarrassing/damning video I want to post online you can bet your ass I'm going to scrub off any metadata.
If there could be some repercussions (e.g. police brutality, gang violence, whistleblowing, etc.) I'm going to go above and beyond to make it not traceable to me. And you're here asking the government to make it a law to make all video outputs traceable to the creator?
I think it’s a thought experiment and not a suggestion. And the transmitter is for the person being videotaped, not the person creating the video. Though of course you raise a good point about anonymity of the video creator.
Videos should be signed by cameras, using keys only those cameras have, at the time the videos are made. Sure, this means they have to be online so their manufacturers can supervise and record key generation, but that's simple now.
