Masking password in Soap Body

Currently I am integrating with a Salesforce Instance that utilizes web services, specifically SOAP. I need to include the password in the body of outbound calls to authenticate. I am including WSS in outgoing calls with username and password.

From my understanding since I have the username and password in Base Config, they are automatically hidden in VA when I preform my call. However, I know that it is not best practice to have passwords in plain text.

I was wondering if anyone had a similar situation where you need password in Outbound Body and how you were able to encrypt it. It would be nice if we could do $plan.password$ but I have had no success finding a way to include password not in plain text. Any advice is welcomed.

Thank You!