[abalone]

Not obvious. p55: “changing the iCloud password won’t invalidate existing backups.“

But you’re right, the paper doesn’t say they do encrypted iCloud backups yet. The infrastructure is there to store encrypted backup keys in the keychain and escrow them so they’re recoverable yet Apple never has access. It’s probably the same foundation for iMessages in iCloud which they are just rolling out. That lets them store your very sensitive messages in the cloud and restore them to new devices and reset your password, all without them ever having access to your keys.

See the section on keychain escrow and recovery for more detail. It’s a game changer and makes storing data in adversarial clouds feasible.

[comstock]

Yes, they obviously have the infrastructure to do it. However, they don’t even optionally.

Part of the reason is that people sometimes forget their passwords and that would lock them out of their backups. So they want to allow email/other methods of resetting the password and giving access to data.

But it would be nice to have it as an option. It’s worrying though that even technical people seem to believe it is end-to-end encrypted. When it very obviously isn’t.

[abalone]

No, Apple doesn’t need to know your backup key to reset your password and retain backups. I explained why in my previous comment. If they’re not stuffing it in iCloud Keychain (yet) it’s not because the infrastructure can’t support it in principle. See: iCloud Keychain recovery. It’s probably just a matter of maturity; they still haven’t rolled out iMessages in iCloud which is a similar case.

[comstock]

I think they want to support the scenario of lost device, lost password, but still allow restoring data to a new device.

[garmaine]

If that were the case you wouldn’t be able to restore from an iCloud backup to a fresh new device. But you can.

[abalone]

In a simpler system yes. But they’ve developed a sophisticated system for syncing secrets called iCloud Keychain. Apple never knows your keychain. Once a new device joins your keychain circle it would in theory be able to sync backup keys and then restore, all without Apple ever knowing. They’re about to roll this out for iMessages which are also not readable by Apple. Backups are probably in the pipeline if they’re not doing it already.

[comstock]

Only if you have multiple devices... it would be nice if they supported this optionally (it would be nice if they supported any kind of end-to-end backup optionally).