# File lib/openid/consumer/idres.rb, line 216
      def check_auth
        Util.log("Using 'check_authentication' with #{server_url}")
        begin
          request = create_check_auth_request
        rescue Message::KeyNotFound => why
          raise ProtocolError, "Could not generate 'check_authentication' "\
                               "request: #{why.message}"
        end

        begin
          response = OpenID.make_kv_post(request, server_url)
        rescue ServerError => why
          raise ProtocolError, "Error from #{server_url} during "\
                               "check_authentication: #{why.message}"
        end

        process_check_auth_response(response)
      end