Resolution:

The AST administrative interface can be configured to require SSL (HTTPS), for example:
==========================================================================
configuration "asta" version "1.1" type "km"
{
        configure kabman
        {
                Configuration
                {
                        serviceName = "TIBCO BusinessEvents Extreme Adminstrator";
                        description = "TIBCO BusinessEvents Extreme Administrator Web Server";
                        listenerAddresses =
                        {
                                "SSL:$HOSTIP:$WEBPORT"
                        };
                };
        }; 
};