| 摘要 |
PROBLEM TO BE SOLVED: To provide an encryption key update system that can synchronously update encryption keys of all devices transmitting/receiving data without the need for users to make troublesome works such as entry of the encryption key and settings. SOLUTION: The encryption key update system has distributed an encryption key list on which a plurality of encryption keys are described in advance to all devices encrypting data by using a common encryption key system, and also distributed a program to select one encryption key or more in the encryption key list on the basis of a prescribed rule to each device. For example, each device selects a 'common encryption key 1' for a period as an encryption key and automatically sets it to a communication environment. After that, each device aborts the 'common encryption key 1' on the border of a date and time and selects a 'common encryption key 2' for the encryption key and automatically sets it to the communication environment.
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