Messages in iCloud, which keeps a user’s entire message history updated and available on all devices, also uses CloudKit end-to-end encryption with a CloudKit service key protected by iCloud Keychain syncing. If the user has enabled iCloud Backup, the CloudKit service key used for the Messages in iCloud container is also backed up to iCloud to allow the user to recover their messages, even if they have lost access to iCloud Keychain and their trusted devices. This iCloud service key is rolled whenever the user turns off iCloud Backup.
If you are in this ecosystem, and feel your potential loss from disclosure is greater than your potential loss by losing/damaging your device, go turn off iCloud Backup — and make sure your keychain is secured to your needs.
Not literally everything. By and large everything, sure. Effectively everything, even. But not literally everything.
For instance, take a deep dive into how e2e encryption works in the Apple ecosystem…
https://support.apple.com/en-us/HT202303
… and why allowing iCloud Backups for usability becomes the weakest link for Apple Messages:
https://support.apple.com/en-au/guide/security/sec3cac31735/...
To save a click:
Messages in iCloud, which keeps a user’s entire message history updated and available on all devices, also uses CloudKit end-to-end encryption with a CloudKit service key protected by iCloud Keychain syncing. If the user has enabled iCloud Backup, the CloudKit service key used for the Messages in iCloud container is also backed up to iCloud to allow the user to recover their messages, even if they have lost access to iCloud Keychain and their trusted devices. This iCloud service key is rolled whenever the user turns off iCloud Backup.
If you are in this ecosystem, and feel your potential loss from disclosure is greater than your potential loss by losing/damaging your device, go turn off iCloud Backup — and make sure your keychain is secured to your needs.