JP2004023138A - Method for backing up secret key and information processing terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for securely restoring a secret key without a cost increase when an IC card is destroyed or missing. <P>SOLUTION: This invention in order to solve the problem provides: the method for backing up the secret key recorded on the IC card characterized in that dividing and encrypting data of the original secret key creates a plurality of divided encryption data and a plurality of other IC cards distributingly record the divided encryption data; and an information processing terminal that installs the method on a personal computer. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to backup of a secret key recorded on an IC card and restoration of a secret key recorded on a lost IC card in a personal computer environment that can be used only by persons limited by the IC card.
[0002]
[Prior art]
A secret key used in PKI (Public Key Infrastructure: a mechanism for authenticating an electronic document using a digital signature by a public key cryptosystem) may be stored in an IC card. Since the secret key is an important thing indicating a personal seal in an electronic environment and must not be leaked, the key is not usually backed up when stored in an IC card. On the other hand, when backing up the private key, special considerations are required for installation and operation of the device so that the data is not leaked.
[0003]
If the IC card storing the private key or the digital certificate is damaged or lost, the information signed and encrypted with the private key and the digital certificate stored in the IC card cannot be used unless the private key is backed up. Further, even if a backup of the secret key is taken, installation and operation of devices for safe storage are required, and a great deal of labor is required. Failure to do so will significantly reduce security.
[0004]
[Problems to be solved by the invention]
With the spread of PKI, it is expected that more and more people will store and use private secret keys and digital certificates on IC cards. Accordingly, it is necessary to provide a mechanism for safely recovering the secret key without incurring a cost when the IC card on which the secret key and the electronic certificate are recorded is damaged or lost.
[0005]
The present invention has been made in view of such a problem, and an object of the present invention is to provide a mechanism for safely recovering a secret key at no cost when an IC card is damaged or lost.
[0006]
[Means for Solving the Problems]
A first invention for solving the problem is as follows.
A method for backing up a secret key recorded on an IC card, wherein the original secret key data is divided by a predetermined number of divisions and encrypted to create a plurality of divided encrypted data, The divided encrypted data is recorded in an IC card in a distributed manner.
[0007]
A desirable mode in the method of the first invention is that, when the divided encrypted data is distributed and recorded on a plurality of other IC cards, even if some of the other plurality of IC cards are lost, the original secret key is retained. A method for backing up a private key, characterized in that the distributed encrypted data is distributed and recorded with redundancy so that it can be restored.
[0008]
A second invention that solves the problem is an information processing terminal including a secret key backup unit that performs a secret key backup process and a backup secret key recovery process according to the method of the first invention. .
[0009]
According to a second aspect of the second invention, in the information processing terminal according to the second invention, the personal authentication information recorded on the IC card determines whether or not the owner of the IC card can use the information processing terminal. The private key backup means distributes the divided encrypted data only to the IC card of a user who is permitted to use the information processing terminal when backing up the private key. An information processing terminal characterized in that the information processing terminal records the information.
[0010]
According to a third aspect of the second invention, in the information processing terminal according to the second aspect of the second invention, the secret key backup means divides the secret key read from the IC card by a predetermined division number. An information processing terminal having a function of creating the divided encrypted data by encrypting the divided encrypted data by an appropriate method and a function of restoring an original secret key from the divided encrypted data.
[0011]
A third invention for solving the problem is an IC card used in the backup processing method according to the first invention, which is internally stored when a backup command including the number of divisions is received from an information processing terminal. A function to divide a secret key by a predetermined number of divisions, encrypt it by an appropriate method, create divided encrypted data and reply to the information processing terminal, and a set of divided ciphers together with a restoration command from the information processing terminal When the encrypted data is given, a function of restoring the original secret key and holding it inside is provided.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an encryption system according to an embodiment of the present invention will be described with reference to the drawings. Here, the encryption system refers to a set of an information processing terminal and an IC card for implementing PKI. FIG. 1 is a block diagram illustrating an entire configuration of an encryption system 1 which is an embodiment of the encryption system according to the present invention. The encryption system 1 records in advance a secret key backup means 11, a card authentication means 14, other application programs 13, a computer 10 having an IC card reader / writer 12, a personal authentication number 50, a secret key 51, and an electronic certificate 52. And an IC card 5. Although not shown, the computer 10 is connected to a monitor display for providing a user with an interactive interface and an input device such as a mouse or a keyboard. Hereinafter, the encryption system 1 will be described with reference to the drawings.
[0013]
The personal computer 10 restricts the user based on the personal authentication number recorded on the IC card, and has a mechanism of not using the personal computer when the unusable IC card 5 is inserted into the reader / writer. Even when the IC card 5 is not inserted into the IC card reader / writer 12, it is not used. When the IC card 5 is inserted into the IC card reader / writer 12, the card authentication means 14 is automatically activated, and checks the personal authentication number of the card to make the above determination.
[0014]
On the IC card 5, a personal authentication number 50 of the owner, a secret key 51 and an electronic certificate 52 are recorded. In the following description and drawings, the owner A, B, etc. of the card is specified and also described as IC cards 5a, 5b, etc. The IC card 5 refers to an IC card without limiting the owner. The same applies to other codes.
[0015]
The secret key backup means 11 is an application program for backing up and restoring the secret key 51 recorded on the IC card 5 inserted in the IC card reader / writer 12.
[0016]
The procedure for backing up the private key will be described below.
(1) The user A who has been permitted to use the personal computer 10 by the personal authentication number of the IC card activates the secret key backup means 11 and instructs the backup of the secret key 51. The secret key backup means 11 arbitrarily determines the number of the secret keys 51 to be divided by the number of registered users who can use the personal computer. The number of divisions may be arbitrarily determined by the user A.
{Circle over (2)} The secret key backup means 11 issues a backup command for the secret key 51 to the IC card 5 to take out the divided and encrypted secret key from the IC card 5 and store it in a personal computer in a secure manner. store. For example, when the number of divisions is set to 3, the number of divisions is given as a parameter to the backup command to instruct the IC card. The IC card 5 responds to the private key backup means 11 with the private key divided data 61, 62, and 63 obtained by dividing the private key 51 into three parts and encrypting them.
{Circle around (3)} When the owner of the IC card 5 restores the secret key data to a new IC card, information necessary for verifying that the owners are the same together with the secret key divided data 61, 62, 63 is included. Record. For example, the personal authentication number recorded on the IC card 5 is recorded. FIG. 2 shows this state. In FIG. 2, a set 110 of data managed for backing up the secret key of the user A is created in the personal computer 10, and the private key divided data 61, 62, 63 and the personal The authentication number 50a is recorded and held.
(4) Next, when a person other than the user A (user B) uses this environment, 61, which is one of the divided data of the secret key of the user A, is automatically changed to the IC of the user B. The personal identification number 50b written on the IC card 5b is written out on the card 5b, and is taken out and stored by a secure method (encryption or the like). At this time, the divided data 61 of the secret key written on the user B's IC card is deleted from the data set 110. FIG. 3 shows this state.
(5) When other users (users C and D) who can use the personal computer 10 use this environment, the above operation (4) is repeated until there is no more divided data of the secret key. When all the divided data 60, 61,... Are written to another IC card, the backup of the secret key of the user A is completed. In the data set 110 of the personal computer 10, personal authentication numbers 50b, 50c, and 50d for specifying the IC card to which the divided data 60, 61,. FIG. 4 shows the personal computer 10 and the data collection 110 in this state.
[0017]
The procedure for restoring the secret key when the IC card is lost is as follows.
(6) The user A who has damaged or lost the IC card prepares a new IC card and instructs the personal computer 10 that has backed up the secret key of the lost IC card to restore the private key.
{Circle around (7)} The secret key backup means 11 is activated. It verifies that the owner of the new IC card is the person who previously backed up the private key. This is determined based on whether the personal authentication number 50a recorded in the data set 110 left in step (3) matches the personal authentication number 50 recorded on the new IC card.
(8) The private key backup means 11 which is instructed to restore, thereafter, every time the owner of the unique information written on the IC card stored in the above (4) uses this environment (this is the data (It can be checked whether the personal identification number corresponding to the personal identification number 50b, 50c,... Recorded in the set 110 is included in the card), and the divided of the owner A previously written on the IC card The private key data 60, 61,... Are taken out and stored in the read data set 110 in a secure manner (in an encrypted state).
(9) When all the divided secret key data 60, 61 and 63 determined in (3) above are ready, insert a new IC card of the owner A into the reader / writer and activate the secret key backup means 11. Then, the divided secret key data 60, 61, and 63 are sent to the IC card 5 together with the command for assembling and combining. Then, the secret key is reconstructed in the new IC card.
[0018]
In order to restore the secret key of the user A, all the other IC cards written by the secret key backup means 11 are required. Therefore, in consideration of the case where the other IC card is gone, (4) The write processing of the data may be made redundant, for example, by making it double or triple.
[0019]
In the above (2), when receiving the backup command of the secret key, the IC card 5 outputs the divided and encrypted data 61, 62,. This assumes that a means for dividing and encrypting the secret key and a means for performing reverse processing and reconstructing the secret key are provided inside the IC card 5. The embodiment is not limited to such an embodiment. What is output from the IC card 5 is the secret key data itself, and the divided encryption may be performed on the personal computer side, that is, by the secret key backup means 11. Alternatively, the division and the encryption may be shared by the IC card 5 and the secret key backup means 11. In any of the embodiments, it is only necessary to obtain a data obtained by encrypting the divided data of the secret key or a data obtained by dividing the data obtained by encrypting the secret key.
[0020]
【The invention's effect】
As described above in detail, the use of the cryptographic system according to the present invention makes it possible to recover the private key safely and at no cost when the IC card on which the private key and the electronic certificate are recorded is damaged or lost. Effect.
[Brief description of the drawings]
FIG. 1 is an overall configuration block diagram of an encryption system 1 according to the present invention.
FIG. 2 is a diagram illustrating a backup operation of a secret key in the cryptographic system 1.
FIG. 3 is a diagram illustrating a backup operation of a secret key in the cryptographic system 1.
FIG. 4 is a diagram illustrating an initial stage of a secret key recovery operation in the cryptographic system 1.
[Explanation of symbols]
5 IC card 10 Personal computer 11 Private key backup means 12 IC card reader / writer 13 Other application means 14 Card authentication means 50 Personal authentication number 51 Private key 61 Divided encrypted data 62 Divided encrypted data 63 Divided encrypted data 110 Backup management data Set of

Claims (6)

A method of backing up a private key recorded on an IC card, wherein the private key data is divided and encrypted to generate a plurality of divided encrypted data, and the divided encrypted data is stored in another plurality of IC cards. A method for backing up a private key, characterized by distributing and recording data. 2. The private key backup processing method according to claim 1, wherein the divided encrypted data is distributed to and recorded on a plurality of other IC cards, even if some of the other plurality of IC cards are lost. A method for backing up a secret key, characterized in that the distributed encrypted data is distributed and recorded with redundancy so that the secret key can be restored. 3. An information processing terminal comprising a secret key backup unit for executing a backup process of a secret key and a recovery process of a backup secret key in the backup processing method according to claim 1 or 2. 4. The information processing terminal according to claim 3, further comprising user authentication means for determining whether or not the owner of the IC card can use the information processing terminal based on personal authentication information recorded on the IC card, The secret key backup means disperses and records the divided encrypted data only on the IC card of a user who is permitted to use the information processing terminal when backing up the secret key. Terminal. 5. The information processing terminal according to claim 4, wherein said secret key backup means divides the secret key read from the IC card by a predetermined number of divisions and encrypts the secret key by an appropriate method to create the divided encrypted data. And an information processing terminal having a function of restoring an original secret key from the divided encrypted data. 3. An IC card used in the backup processing method according to claim 1 or 2, wherein when a backup command including the number of divisions is received, the secret key is divided by a predetermined number of divisions and further divided by an appropriate method. An IC having a function of encrypting and generating the divided encrypted data and responding to the personal computer, and a function of restoring the original secret key when a set of divided encrypted data is given together with the restoration command card.

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