A cool, possible solution would be to have every participant in the video to digitally sign the final file to verify that they're actually in the video, consens

A cool, possible solution would be to have every participant in the video to digitally sign the final file to verify that they're actually in the video, consensually. That way, if anyone finds a deep fake video, it would be easy to dispute it since it doesn't have the person's signature. Of course, this would be exceedingly difficult in practice, since you'd need the signing to be opt-out instead of opt-in for it to be truly effective.