Apple’s own HT202303. It is quite clear on the matter, even going so far as to point out that the keys are rotated when you turn off iCloud Backup.
Read the parts about Messages in iCloud, the service used to sync messages between devices. Those keys are included in the non-e2ee iCloud Backup. Both are enabled by default.
Read the parts about Messages in iCloud, the service used to sync messages between devices. Those keys are included in the non-e2ee iCloud Backup. Both are enabled by default.