Maybe you could have some DRMish thing where the camera signs it with a "secret" key, but this would be terrible for various reasons and also likely broken very fast.
I don't think so. You can cryptographically sign anything much like how SSL works now. You'll have to rely on certificate authorities to assign these certs, but it works.
Videos should be cryptographically signed, and verified once online. You can spoof certs but you can't really fake the cert authority
But, signing some data with a certificate only indicates that a key belongs to a particular name. It doesn't tell you whether the person or organization with that name is trustworthy.
That's what I meant by "validated by this source". But unlike with CAs, where they're (meant to) just base issuance on the simple objectively testable criterion of whether you control the domain in question, an external authority cannot easily know whether a video represents real events, whatever that means.
