In the system which stores data sent out from an external equipment temporarily in a storage apparatus to output, to ensure the security of data during the storage period, there has been a conventional technique for the encryption of all received data. However, the encryption of all received data causes an increase of the load on the encryption processing and it causes such problems that much time is spent in processing of the system and efficiency is bad. In the invention, a NIC determines whether or not the data received from a host apparatus requires the encryption, and when it is determined that the data requires the encryption, the encryption processing of the data is carried out.