Password Protection and Encryption can now be enabled via spacedesk Driver Console - CONTROL - "Password Protection and Encryption" check box.

This feature is only available for BUSINESS/COMMERCIAL LICENSED Android Viewer app.
In case of password renewal, just click the "New" button beside the Password text box. 

FYI: This feature is also pre-requisite for the Remote Keyboard Control over network connection in Business licensed Android VIEWER app.