> No, architecturally there's no reason to do it on the client side. The architectural reason is to do things the server couldn’t. > You're uploading a photo

> No, architecturally there's no reason to do it on the client side. The architectural reason is to do things the server couldn’t. > You're uploading a photo to iCloud, encrypted with a key that Apple controls. The architectural reason is so the server doesn’t have to be able to read the photo, and it need not be a key Apple controls. Your first two sentences are the exact reason to do it on the client instead of on the server, such that it’s possible to have e2e encryption opaque to the server.