> I wonder what encryption and key based techniques can be used to verify the authenticity of audio and video records in the future.

None, since encryption isn't the answer to this problem. Take Romney's leaked "47%" comment [1] or Hillary Clinton's leaked "deplorables" comment, how would encryption have been useful to either verify the recordings' authenticity or reject them if they had been a deepfakes? It wouldn't have, as those comments were meant for private audiences, so neither of them would have officially signed them. If the encryption could trace the recording back to the individual that made it, then the leaker might decide never release the recording (since they don't want to be outed). And if all the encryption can do is trace back to a random device, why not just get a random device to sign your deepfake?

[1] https://www.npr.org/sections/itsallpolitics/2012/09/17/16131...

[2] https://www.npr.org/2016/09/10/493427601/hillary-clintons-ba...

There are DRM and signing schemes, stegonography, etc, but in the moment, people don't care. Or rather, the message registers in their minds whether it happens to be true or not. It's how advertising works. Beliefs are essentially tribal, and we all believe our tribal sources. If a source of news isn't a part of your tribe, you're probably not going to believe what it's saying until someone from your ingroup verifies it. Crypto doesn't do that.

The irony is that we all trust crypto because of the perceived tribal affiliation of the developers as well, which doubly reduces the case for crypto verifying media.

We can barely get actual security devices to keep their keys secret. Do you expect rando Chinese $49 video recorder to have a trusted key management solution?