Cryptography – Key management
Reexamination Certificate
2006-08-22
2010-11-02
Nguyen, Minh Dieu (Department: 2438)
Cryptography
Key management
C380S278000, C713S189000
Reexamination Certificate
active
07826619
ABSTRACT:
In a key-insulated cryptosystem according to the present invention, a plurality of external devices are associated with a number of updates of a terminal secret key which has already been updated, and a different piece of secret information is stored in each of the external devices. In addition, a key-updating method in the key-insulated cryptosystem according to the present invention includes steps of: selecting one of the external devices depending on the number of updates of the terminal secret key; and causing the selected external device to generate key-updating information used for updating the terminal secret key based on the number of updates and the stored secret information.
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Nguyen Minh Dieu
NTT DoCoMo Inc.
Oblon, Spivak McClelland, Maier & Neustadt, L.L.P.
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