https://stopncii.org/how-it-works/ explains that "Your content will not be uploaded, it will remain on your device", and "Participating companies will look for matches to the hash and remove any matches within their system(s) if it violates their intimate image abuse policy."
In principle, both promises can be kept, with humans checking the matches (if any) against their rules. (In practice, I have no idea how it will work out.)
In principle, both promises can be kept, with humans checking the matches (if any) against their rules. (In practice, I have no idea how it will work out.)