This requirement would be done at the Java level. So in your Java proxy classes, ensure you have the correct application logic to consume the encrypted SOAP call. There is no configuration setting on the AEM side. All the logic has to be within Java app logic. Have a look at the article shared by Ratna.
As shown in this article, you need to create Java proxy classes using a tool like CFX. THen you place the proxy classes into an OSGi bundle and now the bundle knows how to invoke the 3rd party web service.