Comment by odo1242

The actual system is that they used a relatively complex zero-knowledge set-matching algorithm to calculate whether an image was a match without downloading or storing the set of hashes locally.

That said, I think this is mostly immaterial to the problem? As the comment you’re responding to says, the main problem they have with the system is mission creep, that governments will expand the system to cover more types of photos, etc. since the software is already present to scan through people’s photos on device. Which could happen regardless of how fancy the matching algorithm was.