answer (OpenID::Server::CheckAuthRequest)

    # File lib/openid/server.rb, line 114
          def answer(signatory)
            is_valid = signatory.verify(@assoc_handle, @signed)
            # Now invalidate that assoc_handle so it this checkAuth
            # message cannot be replayed.
            signatory.invalidate(@assoc_handle, dumb=true)
            response = OpenIDResponse.new(self)
            valid_str = is_valid ? "true" : "false"
            response.fields.set_arg(OPENID_NS, 'is_valid', valid_str)

            if @invalidate_handle
              assoc = signatory.get_association(@invalidate_handle, false)
              if !assoc
                response.fields.set_arg(
                        OPENID_NS, 'invalidate_handle', @invalidate_handle)
              end
            end

            return response
          end