Some smartphone cameras already have this. Samsung tried it on the S25 but apparently did it wrong (https://petapixel.com/2025/02/13/samsungs-image-authenticity...). Google has it on the Pixel 10 line.

I think it's very likely the next iPhone will have some form of authenticity proof too, I just hope Apple doesn't go with its own standard again that's incompatible with everything else.