# File lib/faye/websocket/draft76_parser.rb, line 23
      def handshake_signature(head)
        return nil if head.empty?
        env = @socket.env

        key1   = env['HTTP_SEC_WEBSOCKET_KEY1']
        value1 = number_from_key(key1) / spaces_in_key(key1)

        key2   = env['HTTP_SEC_WEBSOCKET_KEY2']
        value2 = number_from_key(key2) / spaces_in_key(key2)

        @handshake_complete = true

        Digest::MD5.digest(big_endian(value1) +
                           big_endian(value2) +
                           head)
      end