| 摘要 |
PURPOSE:To minimize secret information to be managed by each member and to allow the method to flexibly cope with subscription / withdrawal of a member by allowing the ciphering information repeater to act like a management center of a secret key. CONSTITUTION:A subscriber caller terminal equipment A3 ciphers information by using an open key OM 1 and sends the ciphered information to a communication line 2, a ciphering information repeater 1 receives the information and decodes the information into a plain text with a secret key SM 1. Then the repeater 1 ciphers again the plain text information with an open key OB 2 of a subscriber terminal equipment B and sends the ciphered information to the line 2. A terminal equipment B3 receives the information and decodes the information into a plain text with its own secret key SB 3. In the case of re-ciphering by the repeater 1, the repeater 1 uses open keys OC2, OD2 similarly to cipher the information and sends the ciphered information to terminal equipments C3, D3, which respectively decode the information into a plain text by using their own respective secret keys SC3, SD4. The repeater 1 centralizingly manages the open key information of each subscriber in this way and each subscriber has only to combine the common open key OM1 with its own open key and secret key. Thus, a subscriber's subscription/withdrawal is implemented by having only to rewrite data of the repeater 1. |
