| 摘要 |
PROBLEM TO BE SOLVED: To provide a key updating method capable more flexibly updating a key without deteriorating the security of encrypted information, a key segregation type encryption system and a terminal device. SOLUTION: In this key segregation type encryption system, a plurality of external apparatuses (external apparatuses 40A, 40B) are associated with the number of times of update of an already updated terminal secret key, and different secret information is stored in each of the external apparatuses. Also, the key updating method of this key segregation type encryption system is provided with a step of selecting an external apparatus depending on the number of times of updating the terminal secret key, and a step in which the selected external apparatus generates key update information used for updating the terminal secret key on the basis of the number of times of update and the stored secret information. COPYRIGHT: (C)2007,JPO&INPIT
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