[nan60]

Fair question, and it actually depends on how iMessage is being backed up to iCloud (sorta). By default, iMessage is included in your iCloud device backup, which when Advanced Data Protection is disabled, is NOT E2E encrypted. That said, if Messages in iCloud is enabled, which instead syncs your messages to iCloud, They are always E2E encrypted, regardless of if ADP is enabled [1]. Even more confusingly, if ADP is off, the keys for Messages in iCloud are still stored in your iCloud backup [2]. So essentially, the only way to use iMessage E2E encrypted is with Advanced Data Protection enabled, regardless of if you're using Messages in iCloud or not.

[1] https://support.apple.com/en-us/102651

[2] https://support.apple.com/guide/security/security-of-icloud-...

[walterbell]

> the only way to use iMessage E2E encrypted is with Advanced Data Protection enabled

If iMessage backup relies on ADP encryption, will ADP move to PQ3 Cryptographic Protocol?

[dwaite]

It is data at rest which is different from the exchange of messages themselves.

I believe the backups are protected via AES.