I've thought about this too but I'm not sure this would work. First you could hack the firmware of a cryptographically signed camera. I already read something about a camera like this that was hacked and the private key leaked. You could have an individual key for each camera and then revoke it maybe.

But you could also photograph a monitor or something like that, like a specifically altered camera lens.

Ultimately you'd probably need something like quantum entangled photon encoding to prove that the photons captured by the sensor were real photons and not fake photons. Like capturing a light field or capturing a spectrum of photons. Not sure if that is even remotely possible but it sounds cool haha.