anchor.diff:                  <<Acc/binary, "&", Key/binary, "=", Param/binary>>
               end, <<"">>, SignedArgs),
           ValidationRequestBody = <<?openid_check_authentication_mode, RequestParameters/binary>>,
  -        EndpointURL = wf:q(<<?openid_op_endpoint_key>>),
           {gui_utils:to_list(EndpointURL), gui_utils:to_list(ValidationRequestBody)}
   
       catch Type:Message ->
  
positive.code: %% ====================================================================
  %% Internal functions
  %% ====================================================================
  
  %% discover_op_endpoint/1
  %% ====================================================================
  
negative.code: %% ====================================================================
  prepare_validation_parameters() ->
      try
          % Make sure received endpoint is really the PLGrid endpoint
          EndpointURL = wf:q(<<?openid_op_endpoint_key>>),
          true = (discover_op_endpoint(?xrds_url) =:= EndpointURL),
  
          % 'openid.signed' contains parameters that must be contained in validation request
          SignedArgsNoPrefix = binary:split(wf:q(<<?openid_signed_key>>), <<",">>, [global]),
          % Add 'openid.' prefix to all parameters
  