If my box from which I do backups to BackBlaze B2 is compromised, how can I prevent the attacker from being able to delete my backups?

I have a Ubuntu 16.04 VPS hosting ownCloud. To backup my ownCloud data, I use the following command:

duplicity /var/owncloud/data b2://account_id@bucket_name/folder_to_backup_to 

Then, it asks me for my Backblaze B2 application key. Let's say I were to save this application key somewhere on my machine to automate backups, anyone who compromised my box would be able to delete my backups!

Do you guys have any tips or tricks to prevent this?