Currently it’s only possible to encrypt the database backup but not the file backup. Using certain plugins results in sensitive data being stored in form of pdf invoices which are backed up during file backup.
We’d like to have these backups to be encrypted, too. It should be fairly easy to implement.
This idea was posted in UpdraftPlus - backup/restore plugin on June 5, 2018 by 
Ulrich Esser.
Yes, I’d love to see this feature as well. A simple password encrypted zip file for the backup would be great. That way if someone gets a hold of a backup file somehow, they can’t just unzip it and have access to your config, db and content uploads without knowing the zip master password.
Yes, a password on the zip file would be an important privacy measure for our store site. Ideally restoration handles the password as well similarly to the database encryption.