challenge

# File lib/webrick/httpauth/digestauth.rb, line 75
      def challenge(req, res, stale=false)
        nonce = generate_next_nonce(req)
        if @use_opaque
          opaque = generate_opaque(req)
          @opaques[opaque].nonce = nonce
        end

        param = Hash.new
        param["realm"]  = HTTPUtils::quote(@realm)
        param["domain"] = HTTPUtils::quote(@domain.to_a.join(" ")) if @domain
        param["nonce"]  = HTTPUtils::quote(nonce)
        param["opaque"] = HTTPUtils::quote(opaque) if opaque
        param["stale"]  = stale.to_s
        param["algorithm"] = @algorithm
        param["qop"]    = HTTPUtils::quote(@qop.to_a.join(",")) if @qop

        res[@response_field] =
          "#{@auth_scheme} " + param.map{|k,v| "#{k}=#{v}" }.join(", ")
        info("%s: %s", @response_field, res[@response_field]) if $DEBUG
        raise @auth_exception
      end