| 摘要 |
PROBLEM TO BE SOLVED: To update a common key inside each communication device without needing to exchange information with the outside via a network. SOLUTION: When remotely controlling/monitoring an industrial control device from a manager terminal via the Internet while using a common key system, a plurality of common keys K are time-sequentially generated/updated and held in common key management sections 34 and 44 in the industrial control device and the manager terminal based on a common password code C held in password code storage sections 34a, 44a and time information obtained from time information generation sections 34b, 44b, and encryption/decryption in transmission/reception is performed using the common keys K having the common time information T. COPYRIGHT: (C)2005,JPO&NCIPI
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