In the case that a bridge unit is connected to a network such as an IEEE 1394 bus, copyright holders want to limit the number of apparatuses that can receive a signal.The invention provides at least one reception unit, or more, that is utilized for receiving data requiring copyright protection, connected to a network and by providing a transmission unit for transmitting data requiring copyright protection to a reception unit by utilizing a network, wherein the transmission unit has an authentication means on the transmission side for carrying out authentication for a reception unit and an authentication number counting means for counting the authentication number that is the number of the authentications carried out by the authentication means on the transmission side while the reception unit has an authentication means on the reception side for carrying out authentication for the authentication means on the transmission side and wherein the above authentication number is limited.