That's tricky because it needs to store and verify metadata that the user cannot edit and that allows one to distinguish a "normal" photo from a professional photography of a photo. The only place where this can happen are the camera settings but these are limited on smart phones and it's not easy to discern the two cases. I'm sure someone would print a 10x10 meter fake image, put it at just the right distance, and wait for the best indirect light to prove that the Yeti exists.
Just include a depth sensor, lidar, etc. I'm sure over time that will become increasingly easy to defeat too, but then we can just keep improving the sensors too.
