Apple can decrypt data stored on iCloud, and they scan it already it seems: https://nakedsecurity.sophos.com/2020/01/09/apples-scanning-icloud-photos-for-child

Apple can decrypt data stored on iCloud, and they scan it already it seems: https://nakedsecurity.sophos.com/2020/01/09/apples-scanning-icloud-photos-for-child-abuse-images/ https://nakedsecurity.sophos.com/2020/01/09/apples-scanning-... Which it what makes adding the client side functionality even more problematic. They can easily extend this to scanning all offline content.