To update a cryptographic key without delay.
This system is composed of a cryptographic key server 1 for instructing the update of the cryptographic key in order to improve safety and plural clients 2a, 2b and 2c for receiving instructions from the cryptographic key server 1. Concerning such an enciphered communication network, when updating the cryptographic key through this method, the cryptographic key server 1 successively repeats the transmission of cryptographic key update data and the reception of an ACK signal showing the reception of cryptographic key update data. Then, the clients 2a, 2b and 2c receive the cryptographic key update data, return the ACK signal and store a new cryptographic key but until any permission is applied from the cryptographic key server 1, the former cryptographic key is used and when the reception of the ACK signal from the respective predetermined clients 2a-2c is completed, the cryptographic key server 1 transmits the permission of update to the respective clients 2a-2c through multi-address communication and simultaneously switches the cryptographic key used for the respective clients 2a-2c from the former cryptographic key to the new cryptographic key.
SHIMIZU HIROSHI
HYOZU HARUHIKO
TOMINAGA HIROYUKI
Next Patent: FILE LINKING METHOD FOR DATA TRANSFER