check_signature (OpenID::Consumer::IdResHandler)

    # File lib/openid/consumer/idres.rb, line 205
          def check_signature
            if @store.nil?
              assoc = nil
            else
              assoc = @store.get_association(server_url, fetch('assoc_handle'))
            end

            if assoc.nil?
              check_auth
            else
              if assoc.expires_in <= 0
                # XXX: It might be a good idea sometimes to re-start the
                # authentication with a new association. Doing it
                # automatically opens the possibility for
                # denial-of-service by a server that just returns expired
                # associations (or really short-lived associations)
                raise ProtocolError, "Association with #{server_url} expired"
              elsif !assoc.check_message_signature(@message)
                raise ProtocolError, "Bad signature in response from #{server_url}"
              end
            end
          end