Patent Number: 7,826,619

Title: Key-updating method, encryption processing method, key-insulated cryptosystem and terminal device

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.

Inventors: Hanaoka; Yumiko (Yokosuka, JP)

Assignee: NTT DoCoMo, Inc.

International Classification: H04L 9/00 (20060101); H04L 9/08 (20060101)

Expiration Date: 2019-11-02 0:00:00