There are already plans for metadata signing. I think some high end Canon cameras might do it already. It basically allows proof (via public private key of the hash) that a particular camera took that photo.

The idea is that you can create a chain of custody with an image. Each edit requires a new signature, with each party responsible for verifying the previous chain, to protect their own reputation.

It’s far from perfect, but will help a lot with things like legal cases.