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

A terminal device and key update technology, which is applied in the transmission system, digital transmission system, secure communication device, etc., can solve the problems of key update, threat key isolation type cryptosystem, and inability to solve key update, etc., to achieve The effect of improving safety

Inactive Publication Date: 2007-02-28
NTT DOCOMO INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

That is, there is basically only one external device used by the user in the key isolation type cryptosystem, so there is a problem that the user cannot flexibly update the decryption key.
[0015] For example, when the external device is kept at home, the user cannot update the decryption key while going out.
[0016] Although it is also considered that the user carries the external device, due to loss or theft, it causes other problems that threaten the key isolation type cryptosystem
In addition, although it is also considered to prepare multiple units to enclose the same master key hk * (confidential information) external device, but at this time, the key isolation type cryptosystem is threatened due to the loss or theft of a certain external device, so compared with the case of one external device, the encrypted information the safety of

Method used

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

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Experimental program
Comparison scheme
Effect test

no. 1 approach

[0053] Next, a first embodiment of the present invention will be described. In addition, in the description of the drawings below, the same or similar symbols are given to the same or similar parts. Wherein, the drawings are schematic, and it should be noted that the proportions of various dimensions thereof are different from the actual ones.

[0054] Therefore, specific dimensions and the like should be determined in consideration of the following description. In addition, of course, the relationship and ratio of mutual dimension also contain the part which differs among drawings.

[0055] (The entire schematic structure of a key-segregated cryptosystem)

[0056] FIG. 1 is an overall schematic configuration diagram of a key isolation type cryptographic system according to a first embodiment of the present invention. As shown in FIG. 1 , the key isolation type encryption system of this embodiment includes terminal devices 10A and 10B, a terminal device 20 , a public inform...

no. 2 approach

[0148] Next, a second embodiment of the present invention will be described. Hereinafter, differences from the first embodiment described above will be mainly described.

[0149] (Logical block structure of key isolation type cryptosystem)

[0150] The logical block configuration of the terminal device 10A (10B), the terminal device 20, the public information server 30, and the external device 40 (40B) constituting the key isolation type cryptographic system of this embodiment is similar to that of the terminal device 10A of the first embodiment of the present invention. (10B), the terminal device 20, the public information server 30, and the external device 40 (40B) are the same.

[0151] (1) Terminal device 10A

[0152] In this embodiment, the encryption unit 105 encrypts plaintext m using the following public key pk. First, the encryption unit 105 uses and decrypts the key dk j-1 (The terminal private key after the first update) corresponds to the public key pk j-1 (th...

no. 3 approach

[0178]A third embodiment of the present invention will be described below. In the above-mentioned first and second embodiments, it is necessary to interactively use two external devices (external devices 40A, 40B) to generate key update information for updating the decryption key dk (terminal private key). In this embodiment, the two external devices can be used without interaction. That is, the present embodiment considers improving the user's convenience while securing a certain level of security of a key-separated cryptographic system.

[0179] Specifically, in this embodiment, the decryption key dk is updated every day. The user of the terminal device 20 updates the decryption key dk every day using the external device 40B installed in the OF. Furthermore, the user of the terminal device 20 updates the decryption key dk once a month using the external device 40A installed in his home RG.

[0180] The user of the terminal device 20 does not necessarily have to interactiv...

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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.

Description

[0001] This application is based on and enjoys the benefit of priority of Japanese Patent Application No. P200×-××××× previously filed in 2005; the entire contents of which are incorporated in this application for reference. technical field [0002] The present invention relates to a key update method of a key isolation type cryptosystem, an encryption processing method, a key isolation type cryptosystem, and a terminal device used in the key isolation type cryptosystem. Background technique [0003] With the advancement of information technology, cryptographic systems for encrypting information sent and received are widely used. [0004] In such a cryptographic system, when the cryptographic algorithm used for encryption processing is deciphered, the security of the encrypted information cannot be guaranteed. [0005] However, in reality, rather than the encryption algorithm being deciphered, it is more likely that the encryption key used for the encryption process is leake...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04L9/16H04L9/20
Inventor 花冈裕都子
Owner NTT DOCOMO INC
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