2,451 karma · joined May 15, 2016
"For Messages in iCloud, if you have iCloud Backup turned on, your backup includes a copy of the key protecting your messages. This ensures you can recover your messages if you lose access to your Keychain and your trusted devices. When you turn off iCloud Backup, a new key is generated on your device to protect future messages and isn't stored by Apple."
The key to iMessage backup is stored in iCloud for convenience for the end-user. The password has to be stored somewhere. Other e2e messengers usually don't have message backup or have only manual message backup where you are responsible for not loosing the key.
Apple is not able to access iMessage if you don't enable iCloud backup for iMessage.
https://developer.android.com/training/articles/user-data-id...
https://developer.android.com/reference/android/provider/Set...