Go to the url http://digital-ocean-blis-host/ajax/download_key.php?role=dir to download the public key needed to encrypt the back-up. Example: http://142.93.49.10/ajax/download_key.php?role=dir
Next, inorder to create an encrypted backup of the local lab:
Navigate to the Backup Data tab.
Upload the public key dowloaded in the previous step.
Click on Backup and save the .zip encrypted backup.