JP2000059353A - Data storage system, data storage method and its program recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the reliability as a result of verification from being deteriorated due to expiration of validity or invalidation of a public key without the need for many public keys for parties referring to data. SOLUTION: A user 31 using stored data transmits storage data 36 and its signature 37 to a storage system 38. The system 38 generates a storage signature 58 with respect to the data 36 and the signature 37 by using a storage key after authentication of the signature and stores the storage signature 58 to a storage device 54, reads the signature 58 from the storage device 54 on a reference request from a reference user 63, verifies the signature 58 by the storage key, generates a signature 62 by using a communication key with respect to the data and the signature when the verification is successful, and transmits the data with the signature 62 added thereto to the user 63. The user 63 uses the public key to verify the signature 62 and recognizes its correctness of the received data 60 and the signature 61 simultaneously when the signature is correct.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data storage system in which a storage user stores data in a storage system, and a reference user refers to the data, a storage method, and a program recording medium.

[0002]

2. Description of the Related Art Generally, as a method of protecting against the threat of fraud (eavesdropping / falsification, etc.) on stored data, encryption and storage for confidentiality or storage by associating an original with a digital signature to prevent tampering. Methods of storing in a detectable manner are widely known. As the secret encryption used there, DES and RSA encryption in the United States and FEA in Japan
L and MISTY encryption are known as products, and as encryption technology for realizing an electronic signature, DSA, RSA,
In Japan, ESIGN etc. are known.

[0003] In the tampering / spoofing detection method, a public encryption method is used, and a secret key is used as a digital signature creation key, and a public key is used as a digital signature verification key. Then, in order to store or distribute the correct public key, the authentication system (C
A) is used, and a communication method using a public key certificate issued by the third party is widely known. On the other hand, the public key (digital signature verification key) stored in the CA
Is open to the public, it is exposed to the threat of a private key (digital signature creation key) being decrypted based on the public key (digital signature verification key) by a third party, and the expiration date is set. General. Further, when the private key is lost or the public key is decrypted, a procedure for invalidating the public key held by the CA is performed. When a public encryption method is used, a public key whose expiration date has expired or has been revoked can be verified as a digital signature, but the verification result is regarded as unreliable. In addition, a secret key for creating an electronic signature needs to be kept secret, and a dedicated device such as an IC card for storing a secret key is used, so that internal information cannot be retrieved from the outside.

FIG. 7 shows a conventional apparatus configuration when a user stores data in a data storage system and refers to the data. FIG. 8 shows a state in which data is stored in a user terminal and a storage server. FIG. 9 shows a processing flow when the user terminal and the storage server refer to data. In the prior art, when a user first saves data, the electronic signature 3 is created on the storage user terminal 16 using the electronic signature creation means 18 based on at least the user's electronic signature creation key 19 and the data 2 to be saved. Create (STE
P1), the received data 1 including the data 2 and the electronic signature 3 is created, and the data storage system 4 is
(STEP 2).

When the data storage system 4 stores the data 2 of the storage user, the communication means 6 receives at least the received data 1 including the data 2 to be stored and the electronic signature 3 given by the storage user. The data archiving server 5 (STEP 3) uses the received data 2 and 3 and the public key acquisition means 7 to authenticate the data by the electronic signature verification means 9 based on the public key 8 of the correct storage user acquired from the authentication system 25. Is not altered (STEP 4). After confirming that the data has not been tampered with, the data storage device 11 uses the data storage device access means 10 to store the data in the data storage device 11 as a data pair 12 so that the relationship between the storage data 2 and the electronic signature 3 can be recognized (STEP 5).

On the other hand, when the reference user refers to the stored data, the data storage system 4 accepts a data reference request by the communication means 6 (STEP 6), and stores the stored data pair 12 by using the data storage device access means 10. The data is read from the storage device 11 (STEP 7). Then, based on the stored data of the data pair 12, the electronic signature and the public key 8 of the correct storage user obtained from the authentication system 25 using the public key obtaining means 7, the data is altered during the storage period by the electronic signature verification means 9 based on the correct storage user's public key 8. Confirm that it has not been performed (STEP 8). After the confirmation, the data is transmitted to the reference user terminal 20 as transmission data 15 including at least the storage data 13 and the electronic signature 14 stored in the reference user terminal 20 (STEP 9). Then, the reference user terminal 20 receives the electronic data 15 including the digital signature 14 of the storage user from the storage system 4 (STEP 10), and obtains the electronic signature acquisition means 2.
4, the correct digital signature verification key 2 of the storage user at that time
3 (STEP 11), and the digital signature verification unit 22
Verify that the data pairs 13 and 14 received are not falsified (STEP 12). If this verification passes, the correct data can be referred to.

[0007]

Now, consider a user A who stores data and a user B who refers to the data. In the conventional data storage system, it is necessary for the user B to store the electronic signature given by the user A in advance together with the storage data and to verify the stored data and the electronic signature when the user B refers to the electronic signature. At this time, when referring to data stored by a plurality of different users, the user B must obtain the public keys for the number of stored users. Therefore, there is a problem that the number of public keys that must be acquired increases as the number of stored users increases.

[0008] Further, when the digital signature is stored in the storage system for a long period of time, the public key required to verify the electronic signature has expired or has been revoked by the user, and the verification result is not reliable. There was a problem that it became impossible. As described above, in order to perform data storage using an electronic signature, a data tampering detection method that is irrelevant to the user who stored the data and that is not affected by the expiration date is required.

[0009] The present invention has been made in view of the above, and an object of the present invention is to prevent a user to refer to from requiring a large number of public keys, and to provide a verification result by expiration or invalidation of a public key. An object of the present invention is to provide a method for storing data that prevents a decrease in reliability.

[0010]

In order to achieve the above object, a data storage system according to the present invention comprises: means for generating both a digital signature creation key and a verification key as a key pair storage means;
It has an electronic signature creating means and an electronic signature verifying means, and holds therein a generated key pair (an electronic signature creating key and an electronic signature verification key). Then, an electronic signature of the input data is generated and output using the signature creation key. The digital signature verification key retained inside verifies the input data and the corresponding digital signature and outputs the verification result to the outside of the device.

[0011] Further, the data storage system of the present invention comprises:
In addition to the conventional data storage system, the data storage server has a communication digital signature generation key and a storage digital signature generation key separately, and at least the storage digital signature key pair is not stored to the outside. Having means. Further, in the data storage method of the present invention, in the data storage system of the present invention, in addition to the electronic signature given by the storage user terminal to the storage data, a storage electronic signature of the storage server (this is the storage data and the user A digital signature created by the terminal is added to the combined digital signature) and stored. When referring to the stored data, the digital signature for storage is verified in the above key pair storage means, and the stored data is altered. After confirming that there is no electronic signature for storage, an electronic signature for communication specified by the storage server is created and given in the key pair storage means instead of the electronic signature for storage, and transmitted to the reference user terminal.

Further, in the data storage method of the present invention, the reference user terminal obtains a message received from the data storage system, obtains a communication verification key (public key) determined by the data storage system from the authentication system, and stores the data. Verifies the electronic signature for communication of the system. (Operation) As described above, in the data storage method of the present invention, when a user terminal stores data, the user terminal adds his / her own electronic signature and transmits the data to the data storage system.

The data storage server verifies that the received data has not been tampered with the storage user's electronic signature verification key, and stores the electronic signature generated with the electronic signature generation key generated in advance so as not to be output to the outside. And store it in the storage device. When the user terminal refers to the storage data, the storage server verifies the storage electronic signature with the electronic signature verification key created in the key pair storage means so that the storage data is not output to the outside in advance. After confirming that there is no digital signature for communication, the digital signature for communication determined by the storage server is added to the entire storage data and the digital signature of the storage user and transmitted.

The referenced user terminal verifies only the communication electronic signature of the data storage server to detect tampering during communication by detecting tampering during communication from the data storage system.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention. The terminal 31 of a user who wants to store data includes a signature creating unit 32 for performing a function operation for creating an electronic signature, a secret key 33 for creating an electronic signature, and a communication unit 34 for communicating with a data storage server. I have. The data 35 received by the data storage system 38 is composed of stored data 36, which is the actual state of the data to be stored, and an electronic signature 37 created by the storage user terminal 31 for the data 36 in order to detect falsification during communication. Become. The data storage system 38 includes a data storage server 39, an electronic signature device 47, and a data storage device 5.
4 and the data storage server 39 is the data storage server 3
9 is a communication means 40 for communicating with the outside, a public key obtaining means 41, a public key 42 of a storage user, and a digital signature verifying means 4.
3. Electronic signature attaching means 44, access means 45 to an electronic signature device 47 used when the signature applying means 44 creates an electronic signature, and data storage device access means 46
It has. An electronic signature device 47 as a storage unit of the storage key pair includes an electronic signature verification unit 48 stored in advance in the electronic signature device 47, and an electronic signature using an electronic signature creation key held in the electronic signature device 47. A generating unit 49, a generating unit 50 for generating a key pair (an electronic signature generating key and an electronic signature verification key);
1. a key 52 for creating a digital signature for storage of a data storage server;
It has a verification key 53 for a storage electronic signature of the data storage server. The data storage device 54 has a data group (at least consisting of storage data, a storage user's digital signature, and a storage server digital signature) 55 stored in the data storage device 54, and the data group 55 is storage data corresponding to the storage data 36. 56,
Electronic signature 57 of the storage requester of data 56, storage server 3
Reference numeral 9 denotes a storage electronic signature 58 created using the electronic signature device 47. The data 59 transmitted by the data storage system 38 is the data 60 requested by the user terminal for storage, the electronic signature 61 given to the data 60 by the storage user, and the data storage server 39 for detecting tampering during communication.
, And an electronic signature 62 created for the entire transmission data including the data 61. The reference user terminal 63 includes an electronic signature verification unit 64, a public key acquisition unit 65, an electronic signature verification key 66 for verifying the communication electronic signature 62 given by the data storage server, and a communication unit 67. The public key certificates of the storage user, the reference user and the data storage server are stored in the authentication system 68.

Next, a processing procedure at the time of data storage will be described with reference to FIG. Now, consider a case where a user stores data. The storage user terminal 31 of the user uses the storage data 36 and the digital signature generation key 33 to store the digital signature.
Then, an electronic signature 37 is created according to Step 2 (STEP 21). Then, at least the storage data 36 and the electronic signature 37 are combined and transmitted to the data storage system 38 using the communication means 34 as data 35 in a format that can be interpreted by the data storage system 38. The data storage server 39 is a communication unit 40
To receive the data 35 (STEP 23), and to confirm the integrity of the data being communicated,
Using the public key 42 of the storage user terminal 31 obtained in step 1 and the received data 36 and 37 as input, the electronic signature verification unit 43 verifies the public key 42 (STEP 24). This verification confirms that there is no problem, and at least stores data 3
6 and the electronic signature 37 of the storage user as input, an instruction to create an electronic signature for storage is issued by the electronic signature applying means 44, and the electronic signature applying means 44 sends the electronic signature for storage to the electronic signature device 47 by the electronic signature device access means 45. (STEP 25).

The electronic signature device 47 selects the storage electronic signature creation key 52 according to the input instruction (STEP 2).
6). Electronic signature creation means 49 for input data
Creates a storage electronic signature using the storage electronic signature creation key 52 created in advance by the key pair generation means 50 (S
TEP27). The created electronic signature is returned to the electronic signature device access means 45 of the caller (STEP 28).

The data storage server 39 includes the electronic signature device 4
7 is stored in the storage data 56.
The data group 55 is stored in the data storage device 54 by the data storage device access means 46 in association with the storage user signature 57 (STEP 29). Next, a processing procedure at the time of data reference will be described with reference to FIGS.

Now, consider a case where the user refers to data 56 already stored. As shown in FIG. 3, the data storage server 39 receives a reference request from the reference user terminal 63 (STEP 30). Then, the data group 55 including the data 56 specified in the reference request is read using the storage device access means 46 (STEP 31). In order to verify that the read data group 55 has not been tampered with, the digital signature device access unit 45 requests the digital signature device 47 to perform verification (STEP 32).

The electronic signature device 47 selects the storage electronic signature verification key 53 created in advance by the key pair generation means 50 according to the input instruction as shown in FIG. 4 (STEP 3).
3). The verification is performed using the input data 55, the verification key 53 of the storage digital signature, and the digital signature verification unit 48 (STE
P34). The verification result (OK or NG) is returned to the electronic signature device access means 45 (STEP 35).

The data storage server 39 includes the electronic signature device 4
After confirming that the return value from the storage 7 is OK, the storage data 56 and the electronic signature 57 of the storage user are displayed as shown in FIG.
Is requested by the electronic signature providing means 44 to the electronic signature device 47 (STEP 36). The electronic signature device 47 performs the key pair generation means 50 according to the input instruction.
(Step 37 in FIG. 4). An electronic signature creating means 4 using the communication electronic signature creation key 51 for the input data.
In step 9, a communication digital signature 62 is created and returned to the electronic signature device access means 45 (STEP 38).

The data storage server 39 adds the electronic signature 62 for communication of the storage server returned in STEP 38 instead of the electronic signature 58 for storage as shown in FIG. The data is transmitted to the user terminal 63 (STEP 39). The data reference user terminal 63 receives the data group 59 by the communication means 67 as shown in FIG. 5 (STEP 40), and then sends the correct electronic signature verification key 66 of the data storage server to the public key acquisition means 65.
Is obtained from the authentication system 68 (STEP 41).
The electronic signature for communication 62 is verified using the electronic signature verification means 64 to verify that the received data group 59 is not falsified (ST).
EP42). At this time, the received data 59 holds the relationship shown in FIG. 6, and the communication digital signature 62 is created while maintaining the correct relationship between the storage data 60 and the storage user's digital signature 61. The fact that the verification result of STEP 42 is OK also means that the verification result of the electronic signature 61 of the storage user is OK, and that the acquired data 60 is the same as the data stored by the storage user terminal. It means that they were verified at the same time.

In this embodiment, the description has been made using the key pair of the public key cryptosystem as the storage electronic signature creating means and the verification means. The same effect can be obtained by using Further, each processing in the data storage system can be performed by a computer decoding and executing a program.

[0024]

As described above, according to the present invention, even if the number of stored users is large, the public key required by the referring user is only the public key of the data storage server. Just by verifying the falsification of the communication data, it is possible to confirm the identity of the data that was simultaneously referenced and the data when it was stored. At the same time, the number of access to the authentication system is reduced because the number of required public keys is reduced.

Further, the data storage server stores both the creation key and the verification key of the electronic signature in the electronic signature device, and does not disclose them to the outside. It is possible to provide a data storage method that can lengthen the expiration date and prevent the public key from being expired and the reliability of the verification result from being lowered due to the invalidation of the key by the user because it is not disclosed by the authentication system. .

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a functional configuration of a data storage system of the present invention.

FIG. 2 is a diagram showing a processing flow when data is stored in a user terminal and a storage server according to the present invention.

FIG. 3 is a diagram showing a processing flow on the storage server side when data is referenced between the user terminal and the storage server according to the present invention.

FIG. 4 is a view showing a processing flow on the electronic signature device side when referring to data.

FIG. 5 is a diagram showing a processing flow on the reference user terminal side when referring to data.

FIG. 6 is a diagram showing correspondence between data and an electronic signature according to the embodiment of the present invention.

FIG. 7 is a diagram showing a functional configuration of a conventional device for data storage.

FIG. 8 is a diagram showing a processing flow when data is stored in a conventional user terminal and a storage server.

FIG. 9 is a diagram showing a processing flow when data is referenced between a conventional user terminal and a storage server.

Claims (8)

[Claims] 1. A data storage server, an electronic signature device,
A data storage device, wherein the data storage server comprises external communication means; access means for the data storage device; and access means for the electronic signature device. The electronic signature device has a storage electronic signature creation key. Key storage means for storing the electronic signature verification key for storage so that it cannot be accessed from outside, and an electronic signature created by the electronic signature creation key of the key storage means for the data accessed by the electronic signature device access means. And a digital signature verifying means for verifying a digital signature accessed by the digital signature device access means with the digital signature verification key of the key storage means. The data storage device is accessed by the data storage device access means, and the stored data and its electronic signature are written. A data storage system, which is loaded or read. 2. The data storage system according to claim 1, wherein said electronic signature device also stores a communication electronic signature creation key in its key storage means. 3. The data storage system according to claim 1, wherein the electronic signature device includes means for generating the storage electronic signature creation key and the storage electronic signature verification key. 4. A storage electronic signature creation key and its verification key are stored so that they cannot be accessed from the outside, and a storage electronic signature is created for the storage data requested to be stored by using the storage electronic signature creation key. The storage data and the storage digital signature are stored in a data storage device, and the storage data requested for reference and the storage electronic signature are read from the data storage device, and the read storage data and the storage digital signature are read out. A data storage method, wherein an electronic signature is verified using the storage electronic signature verification key. 5. A communication electronic signature creation key is stored, and a communication electronic signature is created with the communication electronic signature creation key for the storage data whose verification result by the storage electronic signature verification key passes. And transmitting the stored data and the electronic signature for communication to the user terminal that has issued the reference request.
Data storage method described. 6. The data storage method according to claim 5, wherein the user terminal verifies the received storage data and the communication digital signature with a digital signature verification public key. 7. A data storage device stores data in response to a storage request, reads and outputs data from the data storage device in response to a reference request, and stores a storage electronic signature creation key and a storage electronic signature verification key in an external device. In the data storage system that is stored so that it cannot be accessed from the storage device, when there is the storage request, a process of creating an electronic signature for storage with the storage electronic signature creation key for the stored data; A process of storing a storage digital signature in the data storage device; a process of reading the storage data and the storage digital signature from the data storage device when the reference request is received; A recording medium recording a program for executing, by a computer, a process of verifying a storage electronic signature with the storage electronic signature verification key. 8. The data storage system also stores a communication electronic signature creation key, and determines whether or not the verification of the storage electronic signature has passed. A program for executing, by the computer, a process of creating a communication electronic signature with respect to data using the communication electronic signature creation key, and a process of sending the storage data and the communication electronic signature to the terminal that has made the reference request. 8. The recording medium according to claim 7, comprising: