| 摘要 |
A server 10 and a client 20 hold common secret information in respective secret information holding units 13 and 23. A server CRC unit 14 in the server 10 generates a CRC code after adding the secret information to communication data, and transmits the communication data with the CRC code attached. A client CRC unit 24 of the client 20 generates a CRC code after adding the secret information to communication data, and checks whether or not an error has occurred in the communication data on the communication path. Since the client 20 holds the secret information, the client 20 determines that an error has not occurred, and obtains the communication data. On the other hand, a router 30, which does not hold the secret information, is unable to obtain the communication data. This prevents the communication data from being transferred to devices outside an authorized domain.
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