[kortex]

What about reflections? When I worked on media forensics, the reflection discrepancy detector worked extremely well, but was very situational, as pictures were not guaranteed to have enough of a reflection to analyze.

Asking the subject to hold up a mirror and move it around pushes the matte and inpainting problems to a whole nother level (though it may require automated analysis to detect the discrepancies).

I think that too might be spoofable given enough time and data. Maybe we could have complex optical trains (reflection, distortion, chromatic aberration), possibly even one that modulates in real time...this kind of just devolves into a Byzantine generals problem. Data coming from an untrusted pipe just fundamentally isn't trustable.