Some sort of signatures to verify legitimate unmodified photographs (taken with a relatively secure device, e.g an iPhone) seems like a reasonable idea But eve

Some sort of signatures to verify legitimate unmodified photographs (taken with a relatively secure device, e.g an iPhone) seems like a reasonable idea But even then, people will be able to point that camera at a manipulated/generated image (either printed or on a screen). Maybe that one could be solved if the photo included some depth information?