| 摘要 |
PURPOSE: To attain a communication circuit required for mutual certification by executing operation three times in a system having, for example, a tone card and a host terminal connected to each other through a communication line. CONSTITUTION: A tone card 1 sends a 1st random number code and key information to a host terminal 2 (1st processing). The terminal 2 generates a 1st authentication code by ciphering the acquired 1st random number code by the key information and sends the 1st authentication code to the card 1 together with a 2nd random number (2nd processing). The tone card 1 judges matching of the authentication code obtained by ciphering the 1st random number code by the key information with a 1st authentication code, generates a 2nd authentication code based upon the 2nd random number code and the key information at the time of matching and generates a false authentication code consisting of a 3rd random number code at the time of unmatching and sends either one of them to the host terminal 2 (3rd processing). The host terminal 2 verifies the tone card 1 based upon those authentication codes. |
