Hiding secret codes in light protects against fake videos

It's rare that I think an academic paper from a good school that is trending on HN is actively stupid, but this is that paper.

If you're even considering going to go to all the trouble of setting up these weird lights and specialized algorithms for some event you're hosting, just shoot your own video of the event and post it. Done.

"Viewers" aren't forensic experts. They aren't going to engage with this algorithm or do some complex exercise to verify the private key of the algorithm prior to running some app on the video, they are just going to watch it.

Opponents aren't going to have difficulty relighting. Relighting is a thing Hollywood does routinely, and it's only getting easier.

Posting your own key and own video does nothing to prove the veracity of your own video. You could still have shot anything you want, with whatever edits you want, and applied the lighting in software after the fact.

I'm sure it was fun to play with the lights in the lab, but this isn't solving a problem of significance well.

> “Each watermark carries a low-fidelity time-stamped version of the unmanipulated video under slightly different lighting. We call these code videos,”

If this is the only info that's encoded, then that might not be an entirely bad idea.

(Usually, the stego-ing of info can help identify, say, a dissident who made a video that was critical of a regime. There are already other ways, but defeating them is whack-a-mole, if universities are going to keep inventing more.)

> Each watermarked light source has a secret code that can be used to check for the corresponding watermark in the video and reveal any malicious editing.

If I have the dissident video, and a really big computer, can I identify the particular watermarked light sources that were present (and from there, know the location or owner)?

While it does not seem enough to guarantee authenticity, this scheme does seem like it would prevent creating a video from scratch pretending to be taken at a protected location without having express knowledge of the key or the flickering at that moment in time.

Definitely interesting for critical event and locations, but quite niche.

Without having read into this deeper, it sounds like someone could take an original video which has this code embedded as small fluctuations in luminance over time and edit it or produce a new video, simply applying the same luminance changes to the edited areas/generated video, no? It seems for a system like this every pixel would need to be digitally signed by the producer for it to be non-repudiable.

Have a vague memory of some old HN discussion about how known fluctuations in light because of slightly varying electricity frequency have been used already to detect fake video and that databases exist with information about frequencies by location and time for this purpose?

That's a really clever idea!

It will be interesting to see how it ends up being expressed as products.

Nope, it just means the faker has more work to do.

I don't think there's any possible solution that cannot also be faked in itself.

I thought we were finally getting away from that "subtly flickering fluorescent lights" vibe in public spaces that gives 30% of the population headaches. But I guess we're bringing it back. Another victory for AI!