| 摘要 |
PROBLEM TO BE SOLVED: To overcome the problem of a conventional method for updating a secret key between the opposite stations of a data concealing unit such that the time information of a timer IC is shifted between the opposite stations and manual resetting of the timer IC is required along with setting of leap year. SOLUTION: A key setting section 10 takes in key update delay time band data or secret key data from a memory card 2 or a key board 3, sets the key update delay time band data in a timer circuit 11 before starting timer operation, and writes secret key data in one of a memory 12 for key 1 or a memory 13 for key 2. In a key update delay time band where the timer circuit 11 is operating, secret key data before and after update coexist in both memories 12, 13, the secret key data before update is erased upon time out and communication can be sustained with updated secret key data. Consequently, the secret key can be updated without using real time information. |
