The iPhone Pro starts at $1199.
Moreover, LiDAR is essentially a laser that emits at a particular wavelength and a camera that detects that wavelength, so it could be fooled by pointing it at a screen that emits at the same wavelength, which in turn could be an ordinary screen with something in front of it that converts light at a wavelength it emits to the one the LiDAR sensor is expecting.
And that's if you insist on using light. The LiDAR sensor itself is an analog piece of hardware that converts the light into an electrical signal, so if you substitute its electrical output as the input to the signing hardware then it signs whatever you want and never knows the difference.
The hardest part about this is probably creating a credible depth map of a generated 2D image, which is the part that doesn't require signatures or attestation.
> The technology need not be 100% tamper-proof to affect society: there is a huge difference in persuasiveness between the claim that anyone could have created a particular video by submitting to an AI some starting videos and images and a few prompts and the claim that anyone with years of technical training and experience could have bought 500 iPhones and used very expensive equipment to create 499 ruined iPhones and one iPhone that Apple's engineers have not detected yet that can be used to create falsely attested recordings.
Until one of the people with the capacity to do it sets up a website where anyone can submit an image and have it signed.
Moreover, isn't "most people can't do this but some people still can" actually worse? It's a system for providing undue credibility to the forgeries from the people who can do it.
Without even making most legitimate images more credible, since most phone cameras don't have fancy LiDAR hardware.