| 摘要 |
PROBLEM TO BE SOLVED: To provide a ciphering method and a cipher system based on an ID which enables the updating of a key. SOLUTION: This cipher system is composed of a communication network 1, a database 10, a key management server 20, a user terminal 30a, and a user terminal 30b. The database 10 stores the number of times of updating decipher keys issued for the terminals 30a, 30b and a group of functions, and discloses the number of times of updating cipher keys and the group of stored functions to the terminals 30a, 30b. The server 20 issues decipher keys or cipher keys to the terminals 30a, 30b, and manages the number of times of updating decipher keys or the group of functions used for generating the cipher keys which have been issued to the terminals 30a, 30b. COPYRIGHT: (C)2004,JPO
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