Hmm, not quite: step 1 - As others have pointed out, there are plenty of ways of getting an image onto someone's phone without their explicit permission. Whats

Hmm, not quite: step 1 - As others have pointed out, there are plenty of ways of getting an image onto someone's phone without their explicit permission. WhatsApp (and I believe Messenger) do this by default; if someone sends you an image, it goes onto your phone and gets uploaded to iCloud. step 2 - TFA proves that hash collision works, and fooling perceptual algorithms is already a known thing. This whole automatic screening process is known to be vulnerable already. step 3 - Humans are harder to fool, but tech giants are not great at scaling human intervention; their tendency is to only use humans for exceptions because humans are expensive and unreliable. This is going to be a lowest-cost-bidder developing-country thing where the screeners are targeted on screening X images per hour, for a value of X that allows very little diligence. And the consequences of a false positive are probably going to be minimal - the screeners will be monitored for individual positive/negative rates, but that's about it. We've seen how this plays out for YouTube copyright claims, Google account cancellations, App store delistings, etc. People's lives are going to be ruined because of this tech. I understand that children's lives are already being ruined because of abuse, but I don't see that this tech is going to reduce that problem. If anything it will increase it (because new pictures of child abuse won't be on the hash database).