I think the situation is clear when we think of this development from a threat modelling perspective. Consider a back-door (subdivided into code-backdoors and

I think the situation is clear when we think of this development from a threat modelling perspective. Consider a back-door (subdivided into code-backdoors and data-backdoors) placed either on-device or on-cloud. (4 possibilities) Scanning for CP is available to Apple on-cloud (in most countries). Scanning for CP is available to the other countries on-cloud (e.g. China users have iCloud run by a Chinese on shore provider). Scanning for CP is not available to Apple on-device (until now) This is where the threat model comes in. Intelligence agencies would like a back door (ideally both Code and Data). This development creates an on-device data-backdoor because scanning for CP is done via a neural network algorithm plus the use of a database of hashes supplied by a third party. If the intelligence service poisons the hashes database then it won't work because the neural network scans for human flesh and things like that, not other kinds of content. So the attack works for other sexual content but not political memes. It is scope-limited back door. For it to be a general back door, the intelligence agency would need the neural network (part of apple's on-device code) and well as the hashes database to be modified. So that is both requiring a new code back door (Apple has resisted this), and a data back door both on-device. Currently Apple has resisted: Code back doors (on device) Data back doors on device (until now) and Apple has allowed Data back doors in cloud (in certain countries) Code back doors in cloud (in certain countries) In reality the option to not place your photos in iCloud is a euphemism for "don't allow any data backdoor". That is because iCloud is a data-backdoor due to it being able to be scanned (either by Apple or an on-shore data provider). My analysis is that the on-device scanning does not improve Apple's ability to identify CP since it does so on iCloud anyway. But if my analysis is incorrect, I'd be genuinely interested if anyone can correct me on this point.