If you are subject to regulatory compliance or are worried about your backup host having access to your encryption key, then you can block them from access your key by unchecking the following box under the Backup > Settings.
The initial value of this setting was specified by the user when they originally installed the software.
We can't tell you the number of times though when we've had clients lose their passwords and thus be unable to reinstall their software or perform restores. As such, we highly recommend that you keep this box ticked and choose a trusted backup host who is compliant with the regulations you need to be compliant with.