I think the idea that Apple is just moving rote hash calculations from the server to the phone - and therefore they were “surprised” anyone cared - does a disse

I think the idea that Apple is just moving rote hash calculations from the server to the phone - and therefore they were “surprised” anyone cared - does a disservice to the smart people at Apple. They’re not dummies and they didn’t think this would be an easy sell. The question of whether we can and should build client-side scanning has been a huge and controversial issue in our community since at least 2019 — when AG William Barr wrote an open letter to Facebook requesting these features. As a cryptographer who works on E2EE I’ve been reading opinion pieces on this, writing pieces and attending Stanford-hosted workshops since that time. Many people attended those workshops from child safety groups, policy think tanks and other tech firms. Apple was also invited and declined to attend. But to imagine they didn’t realize how controversial these systems would be — that defies belief. They would have to be living in a cave, and the Apple security leaders don’t live in a cave. The Apple system was clearly designed to enable scanning on E2EE backup files. The fact that iCloud isn’t E2EE right now is amusing, but I think it’s safe to assume that they want to enable that feature but felt they needed this coverage. Apple doesn’t share their reasoning, but it’s fairly obvious they felt some strong pressure — largely instigated by government agencies and members of the Senate - to implement some kind of “voluntary compromise” here. This is the one they chose. Where they were surprised, I think, is that there was so much broad negative reaction beyond the usual suspects like privacy groups. As you said, server-side scanning is already ubiquitous so what’s the big deal? My suspicion is that “server side scanning of your private files is ubiquitous” is something that is only actually well-known to tech experts. Most of the general public is ignorant about all this, and they only really get a chance to react to any of this technology when something big makes it national news: as Apple did this summer. (Putting it on your phone and making it apply to private backup photos rather than shared albums, as some cloud providers have in the past, also didn’t help.)