> it's trivial to block the projector and hide the dot pattern. No dot pattern = iPhone thinks the object is far away, which is what happens in landscape photos.

I've never looked at the LiDAR hardware, but where is the emitter in relation to the receiver. Why would the LiDAR not reflect off of whatever you're blocking it with and return a very short flight meaning it was very close?

> all three iPhone cameras simultaneously, ideally as a 2-3s video, and use the parallax/multiple perspectives to extract depth information.

I think optics could be used to make each camera see a different image.

A video could show shake, which could be verified against readings from the phone's accelerometer -- but you could just hold it still and claim that it was on a tripod.

I don't think it's an either or - additional data signals that need to correlate to authenticate will increase confidence. You can use multiple other signals to evaluate whether something is truly a landscape photo, and in that case not require a LiDAR capture, but if you are inside and at close range then you could assume that it should be part of scoring the authentication.

Similarly, LiDAR alone will help disqualify cases where someone is just taking a picture of e.g. a landscape target of the Golden Gate, but that it shown on a screen 1 meter away.

Right but I’d argue that realistically this feature is going to be most useful when taking photos of things reasonably close by, people especially, rather than landscape photography.

This approach makes me wonder if the future is actually going to move towards visual cryptography.