code: public File getRadiusKeyFile() throws GuacamoleException {
          return environment.getProperty(
              RadiusGuacamoleProperties.RADIUS_KEY_FILE,
              new File(environment.getGuacamoleHome(), "radius.key")
          );
      }
docs: Returns the key file for the client for creating encrypted
  connections to RADIUS servers as specified in
  guacamole.properties.  By default a file called radius.pem
  is used.
  
  @return
  The file name for the client certificate/key pair
  for making encrypted RADIUS connections.
  
  @throws GuacamoleException
  If guacamole.properties cannot be parsed.