Is it possible to develop a camera that takes pictures in a special format that records an encrypted signature, some kind ledger technology for images?

The idea is authenticity of images could be challenged. If in doubt, the original photographer or source can provide verification - automated or otherwise, that only superficial X, Y, or Z edits have been made such as lighting or contrast changes.

Copies of the images would contain this ledger or a link. In the future maybe photos without this technology are never to be trusted as a source, or perhaps disallowed on certain platforms.

So it's inverted from "we must detect fake" to "we must detect authenticity." The latter being easier to control.

I mean, nice things are under threat. There's no escaping it. If technology got us into this mess, technology can dig us out.