JP2001027964A - Data storing method, system therefor and recording medium for data storage processing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the furtive looking of data stored in a storage device with no troublesome operations of a user required by enciphering automatically the data with a writing request and then decoding automatically the enciphered data to transfer them to an application program with a reading request. SOLUTION: This system consists of a terminal 101 which is operated by a user 123, a storage device 111 which is connected to the terminal 101, a key management server (key management computer) 112 which manages a key for enciphering the data, a key data base 121 which stores an enciphering key and a network 122 which connects the terminal 101 to the server 112. When a data writing request is given from an application program 106, the data are automatically enciphered and stored in the storage device 111. Meanwhile, the enciphered data stored in the storage device 111 are automatically decoded and sent to the program 106 when a reading request is given from the program 106.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a computer system having a computer for executing processing in accordance with an application program and a storage device connected to the computer, and stores data processed by the application program in the storage device. The present invention relates to a data storage method and system for writing and storing, and a recording medium for data storage processing.

[0002]

2. Description of the Related Art Conventionally, in a computer system provided with a storage device such as a magnetic disk device, data processed by an application program operating inside the computer has been stored in the storage device as it is. Therefore, the data stored on the storage device can be stolen or rewritten from the computer used to create the data or from a computer on the network if the storage device is connected to a network. There was a risk of confidential leakage or data modification.

Therefore, an operating system managing the storage device is provided with an access control function for determining which user can read or rewrite the data stored in the storage device,
There is a mechanism that does not permit access from a user who does not have the right to access. However, since the storage device can be directly accessed without going through the operating system, the access control function cannot completely prevent data snooping and modification. Therefore, measures have been taken to prevent such illegal acts by encrypting the data stored in the storage device or attaching an electronic signature for detecting that the data has been altered.

When encrypting or decrypting data, the data is divided into basic units of 8 bits or 64 bits, and then encrypted and decrypted. However, in this state, the basic unit having the same contents is encrypted into the same cipher text, and thus, it becomes a clue for decrypting the cipher text.
Therefore, when encrypting the basic unit at a certain position in the data, some processing (for example, exclusive OR) is performed using the already-encrypted basic unit at the previous position, and then the encryption is performed. Become By performing such a chain processing of the basic units, it is possible to eliminate clues for decoding. When encrypting the first basic unit of data, a chain process is performed using initialization data prepared separately. The above cipher chain processing is described in, for example, "Encryption and Data Security" (DER Denning, Tadahiro Kamizono et al., Published by Baifukan).

[0005]

However, when data is encrypted and stored, the data is temporarily stored on the storage device, or the user explicitly specifies the data stored on the storage device. Was doing encryption. Similarly,
When decrypting encrypted data, the user explicitly specifies decryption and decrypts the original data. For this reason, the user has to instruct data encryption / decryption each time, and there is a problem that the operation is troublesome. In particular,
If you perform operations such as decrypting the encrypted data once, modifying it, and then encrypting it again, you may forget to re-encrypt the data. However, there is a problem that the data cannot be countered by prying eyes or alteration of the data in the storage device. Therefore, there is a need for a mechanism capable of performing encryption / decryption when data encryption / decryption is required without necessarily giving a direct instruction from a user.

SUMMARY OF THE INVENTION The present invention has been made to solve these problems, and a first object of the present invention is to provide a method for transmitting data from an application program without direct instruction of encryption / decryption by a user. If there is a write request, the data is automatically encrypted and stored in the storage device, and if there is a data read request, the encrypted data stored in the storage device is automatically decrypted and the application program To provide a data storage method and system, and a storage medium for storage processing, which can prevent the data in the storage device from being stolen or altered without performing a troublesome operation by the user.

[0007] Further, in the case of automatically performing encryption / decryption in response to a write request and a read request from the application program, the following problem occurs.
The application program reads and writes data from an arbitrary position in the file. If the encryption basic unit is chained when performing an automatic encryption method, when data is overwritten at a certain position in the file, the process of re-encrypting all the basic units after that position will occur. It becomes necessary, and the time until the end of the overwriting process becomes long.

In order to reduce the portion that requires such re-encryption processing, a method has been considered in which a file is divided by a record having a fixed length larger than the basic encryption unit, and the initialization data is prepared for each record. I have. In this method, when data is overwritten at a certain position in a file, re-encryption processing is performed only up to the end of the overwritten record. By doing this,
The portion that requires re-encryption can be limited.

[0009] However, by dividing the file into records of a fixed length, re-encryption processing at the time of data overwriting can be reduced, but it is not easy to determine how long the record length is good.

If the record length is long, the length of the re-encryption process required when the application program overwrites the data increases. When the record length is short, the application program often accesses over multiple records when reading and writing data, increasing the number of times to prepare the initialization data for each record, and the processing time is rather overhead. turn into.

Further, since the unit length of reading / writing differs for each application program, the optimum record length for one application program is not always optimum for another application program.

A second object of the present invention is to solve the above-mentioned problems. A second object of the present invention is to record the read / write length and the read / write start position of each application program. A data storage method capable of shortening the processing time at the time of data overwriting by obtaining a record size that minimizes the overhead time consisting of re-encryption processing at the time of overwriting and preparation of initialization data, and An object of the present invention is to provide a system and a recording medium for storage processing.

[0013]

In order to achieve the above object, a data storage method according to the present invention, in response to a data write request from an application program, intercepts the write request by the file hook means, Before writing data to be written to the storage device, the data is encrypted in a record length unit set in advance by an encryption key stored in an internal memory of the computer and written to the storage device, and a read request from the application program is sent. On the other hand, before the read request is intercepted by the file hook means, and before the read data is transferred to the application program, the operating system causes the operating system to read the encrypted data from the storage device in record units. , Decrypting the encrypted data in units of a predetermined record length using an encryption key stored in an internal memory, and transferring the decrypted data to the application program that has issued a read request. .

In addition, when a user saves a file in advance, the user specifies a file or a directory to be automatically encrypted, so that only the specified file or a file under the specified directory can be encrypted or decrypted. It is characterized in that

When the operating system receives a data read / write request from an application program, the position and data length of the data in a file are recorded, and after a sufficient number of records are recorded, the application program In each case, a record length that minimizes the overhead of the re-encryption processing and the initialization data processing is calculated, and in the subsequent encryption and decryption, the calculated record length is used. .

By means such as this, it is possible to automatically encrypt data to be stored in the storage device without explicitly instructing the user to perform encryption or decryption, and to decrypt automatically when reading out the data. The user is not forced to perform troublesome operations. Further, since the data to be stored in the storage device is automatically stored, there is no problem that the user forgets to encrypt the data. Also, since a directory representing a storage medium such as a floppy (registered trademark) disk can be designated as a place where the encrypted information is stored, it is possible to prevent important information from being copied and taken out.

In addition, the length of re-encryption in one overwrite request and the record length that minimizes the overhead of the initialization data generation process can be obtained for each application program. Can be shortened for each application program. In addition, the mechanism for intercepting data read / write requests from the application to the operating system does not require rewriting existing application programs and operating systems if provided by the operating system, and additionally requires new hardware. It is possible to increase the security of data at a minimum cost without having to replace.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a detailed description will be given based on an embodiment of the present invention. FIG. 1 is a system configuration diagram showing an embodiment of the present invention. In the present embodiment, a case is described in which a user creates data created by an application program running on a terminal, encrypts the data with his / her key obtained from a key management server (key management computer), and saves the data in a storage device connected to the terminal. In this case, the encrypted data read from the storage device is decrypted with its own key obtained from the key management server, and the plaintext data is transferred to the application.

The system shown in FIG. 1 is roughly divided into a terminal 101 operated by a user 123, a storage device 111 connected to the terminal 101, and a key management server (key management server) for managing a key for data encryption. Key management computer) 112
And a key database 121 storing keys for encryption
And a network 122 connecting the terminal 101 and the key management server 112. The terminal 101
It is configured by a stationary or portable computer, and includes therein a user input unit 102, a password encryption key generation unit 103, and a file encryption key generation unit 10.
4. An encryption key / decryption unit 105, an application program 106, a file access hook unit 107, an operating system 108, a storage device interface 109, a communication interface 110, a record size storage unit 124, and an access information storage unit 125. A storage unit 123 can store and read data files created by the application program 106 in the storage device 111. The user input unit 102 allows the user 123 to input a user name and a password in accordance with an instruction from the file access hook unit 107. The password encryption key generation unit 103 is for generating an encryption key from a password input by the user 123. The password encryption key encrypts the authentication information of the user 123 and the encryption key used in the entire system and stores the encrypted information in the storage device 111. The file encryption key generation unit 104 randomly generates an encryption key used for encrypting a file stored in the storage device 111. The encryption / decryption unit 105 is for actually encrypting / decrypting a file. The application program 106 for the user 123 to create a data file is software such as a word processor or a spreadsheet.

The file access hook unit 107 performs a process of intercepting a file access request from the application program 106 to the storage device 111 and a process of encrypting and decrypting a file at the terminal 101, such as obtaining a user key from the key management server 112. Is to manage. The operating system 108 running on the terminal 101 includes a storage device interface 109, a communication interface 110, and a record size storage unit 12.
4. The storage device 1 manages the access information storage unit 125 and
An operating environment such as access to the Internet 11 and communication via the network 122 is provided to the application program 106 and the file access hook unit 107.

The record size storage unit 124 is used to store a record size for encryption / decryption for each application program.

The access information storage unit 125 stores, for each application program, a plurality of read / write start positions and read / write data lengths in a file, and performs encryption / decryption. Used to calculate the record size at the time. In the storage device 111, not only the file created by the user 123 but also an authentication token used for confirmation when the user 123 inputs a password and a system key used for encrypting data by the system are encrypted and stored. is there.

On the other hand, the key management server 112 includes a key management application program 113, a user input unit 114,
Password encryption key generation unit 115, user key generation unit 11
6, an encryption / decryption unit 117, an operating system 118, a communication interface 119, and a storage device interface 120. The user 123 of the terminal 101 generates information for using the present system, and generates a user key. Has the function of managing. The key management application program 113 manages overall encryption processing in the key management server 112, such as generation of information to be distributed to the user 123 and processing of a user key request message from the terminal 101. The user input unit 114 first displays the user 12
3 allows the user 123 to input a user name and a password in accordance with an instruction from the key management application program 113 when the user key 3 generates a user key.
The password encryption key generation unit 115 is for generating an encryption key from the password input by the user 123. The user key generation unit 116 is for randomly generating an encryption key for the user 123. The encryption / decryption unit 117 encrypts information to be distributed to the user 123, and encrypts or decrypts an electronic message exchanged when the user 123 requests a user key. An operating system 118 running on the key management server 112 manages the communication interface 119 and the storage device interface 120, and sets the environment such as communication using the network 122 and access to the key database 121 to the key management application program 113. To provide. The key database 121 stores a system key for encrypting communication data exchanged between the terminal 101 and the key management server 112 using the network 122, and a key information record of the user 123. Is composed of a user name 201 and a user key 202 as shown in FIG.

(Creation of User Distribution Information) FIG. 3 is a flowchart showing a procedure for creating data to be distributed to the user 123 on the key management server 112 in order to use the present system. First, a user name and a password are input from the user input unit 114 (step 301). Next, the password encryption key generation unit 115 generates a password encryption key by processing the password of the user 123. As a processing method, for example, a one-way function such as the MD5 algorithm is used (step 302). Subsequently, the user key generation unit 116 randomly generates a user key (step 303). A key information record as shown in FIG. 2 is created from the user key and the user name obtained here and stored in the key database 121 (step 304). FIG. 2 is an example of a key information record of the user A whose user name is “A”. Next, an authentication token for verifying the correctness of the password input by the user 123 is created (step 305). Since it is dangerous for the security to store the password input by the user as it is as data, it is stored by using an encryption process. For example, in UNIX (registered trademark), the data of “all 0” is encrypted and stored using the password of the user 123 as a key, and when the user 123 later inputs the password, the same processing is performed to perform the authentication work. ing.

In the present embodiment, the authentication token as shown in FIG. 4 is generated by encrypting the 6-byte data of all "0" with the password encryption key. In FIG. 4, reference numeral 401 denotes a user name (here, user A) indicating the owner of the authentication token, and reference numeral 402 denotes a data value after performing the encryption processing. Subsequently, the system key used to encrypt data flowing on the network 122 in the present system is also encrypted with the password encryption key (step 306). By using the password encryption key, only a person who knows the password of the user 123 can obtain the correct system key. The system key is stored in the key management server 1
In step 12, it is created at the start of system operation. Finally, the authentication token and the encrypted system key are copied to a floppy disk or the like and passed to the user 123 (step 307). The user 123 stores the received information in the storage device 111 connected to the terminal 101 operated by the user 123.
Will be copied and used.

(File Encryption) FIG.
3 is a flowchart showing a procedure for encrypting data created on terminal 101 by user 3 (here, user A) and storing it in storage device 111. This procedure starts when user A attempts to save data created by application program 106 in storage device 111. First, when the application program 106 issues a file save request to the operating system 108, the operating system 108 issues the request before processing the request.
The file storage request is sent to the file access hook unit 10.
7 (step 501). Subsequently, in order to encrypt and save the file requested to be saved, a user key is obtained from the management server 112 as follows. First, the user name and password of the user A who operated the application program 106 are entered in the user input unit 102.
To the user A (step 502). next,
Password encryption key generation unit 10 based on the input password
3 generates a password encryption key (step 503).

The terminal 101 performs the same processing as the generation of the authentication token in the management server 112 in order to confirm whether the input password is correct, and verifies whether or not it matches the authentication token read from the storage device 111 (step). 504). If they do not match, the user is repeatedly prompted for a user name and password. If they match, proceed to the next step.

Next, the encrypted system key is read from the storage device 111, and the system key is decrypted using the password encryption key (steps 505 and 506). In addition,
The authentication token and the encrypted system key read from the storage device 111 have been generated in the key management server 112 in advance.

Next, a message is exchanged with the key management server 112 to obtain a user key. Note that the terminal 101
The format of the message exchanged between the server and the key management server 112 is as shown in FIG. In FIG. 6, reference numeral 601 denotes a header portion for distinguishing a message.
12 indicates a user key request message requesting a user key, and “1” indicates a user key response message indicating a response from the key management server 112. Reference numeral 602 denotes a data body included in the message, the content of which differs depending on the type of the message. 603 is
An electronic signature of the header 601 and the data 602 using the system key. In order to obtain a user key from the key management server 112, the terminal 101 creates a user key request message (step 507). Information sent from the terminal 101 to the key management server 112 is a user name and challenge data. The challenge data is an integer that is randomly selected each time a user key request message is created, and the key management server 112 determines that response data that has been subjected to a predetermined process (for example, adding 1) is included in the user key response message. By doing so, the user can confirm that the received reply message is a reply to the immediately preceding request message. First, data including a user name 701 and challenge data 702 as shown in FIG. 7 is formed, and is encrypted with a system key. Next, as shown in FIG.
A user key request including a value “0” indicating that the message is a user key request message in the header portion 801 and an electronic signature 803 of data including information obtained by encrypting the user name and challenge data in the data portion 802. Generate a message. Then, it sends the generated user key request message to the key management server 112 and waits for a reply message to be sent back.

Thereafter, the key management server 112 processes the user key request message, creates a user key reply message and sends it back to the terminal 101 (step 50).
8), details of this procedure will be described later with reference to FIG. Upon receiving the returned user key response message (step 509), the terminal 101 first checks the electronic signature included in the response message for any changes during transfer (step 510). Here, when it is found that the message has been modified, the application program 106 that issued the file save instruction is notified of the failure of the save, and the process ends (step 521). If there is no change, proceed to the next step. Since the data part of the user key reply message is encrypted with the system key, it is decrypted with the system key (step 511).

By the way, the user key reply message includes
There are two types, one that includes the user key and one that does not include the user key because some error has occurred in the key management server 112, and the contents of the data part of the reply message are different. The contents of this data portion before being encrypted are as shown in FIG. 9 or FIG. FIG. 9 shows the contents when the user key is returned, and includes a user name 901, response data 902, a value “0” 903 indicating that the user key is included, and a user key 904. FIG.
Is the content when the user key is not returned due to some error. The user name 1001 and the response data 10
02, a value “1” 1 indicating that an error has occurred
003. Here, 1003 may include any value other than “0” to indicate a specific type of error. The response data included in the user key reply message is obtained by adding “1” to the value of the challenge data included in the user key request message. After decrypting the data portion of the user key reply message, the terminal 101 checks the presence or absence of the user key (step 51).
2). If the user key is not included, the file cannot be encrypted and saved, so that the failure of saving is notified to the application program 106 (step 5).
21) End. If the user key is included, the procedure proceeds to the procedure for actually encrypting the file.

Here, if writing to a new file, a file encryption key and file initialization data are randomly generated (step 519). Then, after encrypting the file encryption key with the user key, the encrypted file encryption key and the file initialization data are stored as the header of the new file (step 520), and the procedure proceeds to the next procedure. The file encryption key is used to generate an encryption key prepared for each record obtained by dividing the file. The file initialization data is used to generate initialization data for each record.

If writing to an existing file,
The encrypted file encryption key and file initialization data are read from the header of the file to be written (step 514). Then, the encrypted file encryption key is decrypted with the user key to obtain the file encryption key (step 5).
15). Next, the data requested to be written is encrypted (step 516). The details of the encryption procedure will be described with reference to FIG.

The encrypted data obtained as described above is written to a position in the encrypted file corresponding to the write request of the application program 106. As shown in FIG. 11, the encrypted file encryption key is 1101, the file initialization data is 1102, the encrypted file body is 1103, and the signature generated using the user key is 1104 as shown in FIG. An encrypted file 1100 is created and stored in the storage device 111. Therefore, the storage device 111 stores, in the encrypted file body 1103 in which the file generated by the application program 106 is encrypted, the data 1101 in which the file encryption key is encrypted, the file initialization data 1102, and the signature 1
104 will be added and stored. Finally, the end of the storage is notified to the application program 106 which has issued the file storage request (step 518), and this procedure is terminated.

(Decryption of File) FIG.
Transmits the encrypted data stored in the storage device 111 to the terminal 1
11 is a flowchart showing a procedure when reading is performed by an application program 106 operating on the application program 01. This procedure starts when the user A attempts to read data previously encrypted and stored in the storage device 111 into the application program 106. When the application program 106 issues a file read request to the operating system 108, the file read request file access hook unit 107 receives the file read request before the operating system 108 processes the request (step 1201). File access hook part 10
7 instructs the operating system 108 to read the file specified by the read request, and reads the encrypted file from the storage device 111 via the storage device interface 109 (step 1).
202).

Next, in order to decrypt the read file, the user is authenticated in the same procedure as when encrypting the file, and a user key is obtained from the key management server 112. Steps 1203 to 1213 corresponding to the procedure for obtaining the user key are steps 502 to 1213 in FIG.
Exactly the same as 512. At this time, the key management server 11
If the alteration of the user key reply message from step 2 is detected (step 1211), or if the user key cannot be obtained (step 1213), the read file cannot be decrypted, so that the read fails. Is notified to the application program 106 (step 1219), and the procedure ends (step 1219).
18). Only when the user key can be obtained, the encrypted file is decrypted as follows. Here, the file to be read has a format as shown in FIG. 11, where 1101 is a file encryption key encrypted with a user key, 1102 is file initialization data, 1103
Is an encrypted file body, and 1104 is an electronic signature of these three data 1101 to 1103 using a user key.

In FIG. 12, if a user key is included, it is checked whether the encrypted file has been altered or not.
04 is confirmed (step 1214). If it is found that the file has been modified, the failure of reading the file is notified to the application program 106 (step 1219), and the procedure ends. If not, first, the encrypted file encryption key 1101 and the file initialization data 1102 are read from the encrypted file (step 1215).

Next, using the user key obtained from the key management server 112, the encrypted file encryption key 1101 is decrypted to obtain the original file encryption key (step 1216). Subsequently, the encrypted data corresponding to the request of the application program 106 is read from the encrypted file body 1103, and decrypted using the file encryption key obtained by decryption (step 1217). The details of the decoding procedure will be described with reference to FIG. Finally, the decrypted data is passed to the application program 106 (step 1218), and the procedure ends.

(Processing of Key Management Application Program) FIG. 13 is a flowchart showing a procedure when the key management application program 113 operating on the key management server 112 processes a user key request of the user A from the terminal 101. is there. This procedure starts when a user key request message is received from the file access hook unit 107. The user key request message received by the key management application program 113 has a format as shown in FIG. Upon receiving the user key request message from the terminal 101 (step 1301), the key management application program 113 first reads the system key stored in the key database 121 in advance to check whether the message has been modified (step 1302). ), The electronic signature in the request message is confirmed (step 1303). If there is any modification, the operation of extracting the user key described below from the key database 121 is not performed.

To extract the user key from the key database 121, first, the encryption / decryption unit 117 decrypts the user key request message with the system key, and extracts the user name 701 and the challenge data 702 as shown in FIG. (Step 1304). Next, a key information record including the user name obtained here is extracted from the key database 121. If a key information record as shown in FIG. 2 is found,
The user key 202 is extracted (step 1305).

After the modification inspection of the user key request message and the extraction of the user key have been completed as described above, the terminal 1
In step 1306, a user key reply message that replies to "01" is created. Here, the response data to be included in the response message is a value obtained by adding “1” to the challenge data included in the request message, but the content to be included in the data portion of the response message depends on whether the user key was obtained. Changes. When the user key is obtained, as shown in FIG.
02, value “0” 90 indicating that the user key is included 90
3. The data composed of the user key 904, which is encrypted using the system key on the encryption / decryption unit 117, is included in the data part of the user key reply message. If the user key cannot be obtained, the data consisting of the user name 1001, the response data 1002, and the value "1" indicating that the user key is not included is encrypted / decrypted as shown in FIG. The data encrypted using the system key on the part 117 is included in the data part of the user key reply message.
The signature part of the user key reply message includes a header part having a value “1” indicating that the message is a user key reply message,
The data composed of the data part created as described above includes a signature created using the system key. The user key reply message created as described above is sent to terminal 101 (step 1307), and this procedure ends.

(Detailed Encryption Procedure) FIG. 14 is a flowchart showing a detailed procedure for encrypting data requested to be written by the application program 106. This procedure starts when a file encryption key, file initialization data, and write request data are prepared.

FIG. 15 shows a write request from the application. 1501 is a write start position, 1502
Is the length of the write data, and 1503 is the write data. In the write request shown in FIG.
A request is made to write 1503 write data between 800 and 2799. In FIG. 14, first, the record length corresponding to the application program that has made the write request is read from the record size storage unit (step 1401). Record size storage 1
24 stores a record size 1602 for each of various application programs 1601 such as a spreadsheet program and a word processing program, as shown in FIG. If the corresponding record length is not recorded, the default length recorded at the end of the record size storage unit 124 is read. Here, it is assumed that “512” is read as the length corresponding to the application program that has issued the write request.

If the record length is not recorded in the record size storage unit 124, the write request position 1501 in the file and the length 1502 of the write data included in the write request from the application program are stored in this application program. It is stored in the program access information storage unit 125 (step 140
3).

As shown in FIG. 17, the access information storage unit 125 stores a start position 1701 and a write data length 1702 for each application program each time there is a write or read request, and stores a plurality of them. be able to. FIG. 17 shows a case where the write request of FIG. 15 is stored in the access information storage unit 125. The data recorded here is used to determine the record length for encryption after a certain period of time.

Next, the start position of the write request is divided by the record length, and the quotient is used as a record index value indicating the number of the record in the file (step 1404). If a write spans multiple records, calculate for all records. When the record index is obtained from the write request shown in FIG. 15, the quotient obtained by dividing the write start position “1800” by the record length “512” is 3, and the quotient obtained by dividing the write end position 2799 by 512 is 5, so the record to be obtained is The index values are "3", "4", and "5".

Subsequently, a record encryption key for the record of the write destination is calculated using the index value of the record and the file encryption key (step 1405). if,
If a write request needs to be made from the beginning of the record, initialization data for the record is obtained from the file initialization data and the record index value. As these calculation methods, for example, a method in which two data are concatenated and an operation by a hash function is performed can be considered. In the case of the write request in FIG.
Since it is a write request up to the middle of "record 3"
Calculation of the record encryption key of "record 4",
The calculation of the record encryption key of “5” and the initialization data is performed.

Next, it is checked whether the data to be written is an overwrite of the data already stored in the file (step 1406). If it is not overwritten, the write data is copied to the encryption buffer and the process proceeds to the encryption step (step 1411). If it is overwriting, the part necessary for the encryption chain processing and the part requiring re-encryption are read from the file into the encryption buffer at the write start position (step 1407). The part required for the encryption chaining process is the ciphertext used in the chaining process when encrypting data at the write start position, and is the ciphertext immediately before the write start position, and its length is the length of the encryption chaining process. Depends on the method. If the write start position is the beginning of the record, the record initialization data is used as a part necessary for the encryption chain processing, so that it is not necessary to read the part immediately before the write start position from the file. Assuming that the length required for the encryption chain processing in the present embodiment is “8”, the portion required for the encryption chain processing in the write request in FIG. 15 is the encryption from the position “1792” to “1799” in the file. Statement. The portion requiring re-encryption is a portion in which the encryption chain process needs to be performed again by overwriting data, and is from immediately after the write end position to the end of the record including the write end position. The portion of the write request in FIG. 15 that requires re-encryption starts from “2800” immediately after the write end position in the file, and ends at “3” in “Record 5” including this write end position.
071 ”. In FIG. 18,
The part necessary for the encryption chain processing and the part requiring re-encryption are shown.

Subsequently, the portion of the encryption buffer that needs to be re-encrypted is decrypted using the corresponding record encryption key (step 1408). In the write request in FIG. 15, decryption is performed using the record encryption key of “record 5”. Then, the write request data is connected to the data decrypted for re-encryption and written on the encryption buffer (step 1409).

Finally, when the data to be encrypted is prepared in the encryption buffer, the encryption key for the record corresponding to the data, the data necessary for the encryption chain processing read from the file, and the initialization data are used. After the encryption (step 1410), the procedure ends.

(Decoding Detailed Procedure) FIG. 19 is a flowchart showing a detailed procedure for reading and decoding data requested to be read from the application program. This procedure starts when the file encryption key and the file initialization data have been prepared. FIG. 20 shows a read request from the application. 2001 is a read start position, and 2002 is the length of read data.

In FIG. 19, first, as in the case of the write request, the record length corresponding to the application program which has issued the read request is read from the record size storage unit (step 1901). If there is no corresponding record length, the default value is read (step 1902), and the read start position 2001 and its length 2
002 is recorded in the access information storage unit 125 for the application program (step 1903). The calculation of the record index and the calculation of the encryption key for the record and the initialization data are performed in the same manner as in the case of the write request (steps 1904, 1905).

Subsequently, a record corresponding to the read request is read from the file, decrypted using the record encryption key and the initialization data (step 1906), and the procedure ends.

(Calculation of Record Length) FIG. 21 is a flowchart showing a detailed procedure for calculating the record length. This procedure starts when the access information recorded in the access information storage unit 125 in a certain application program exceeds a certain number (for example, 100).
Here, a power of 2 is considered as a candidate for the record length.
This is because a file access unit of an application program or an operating system and a physical recording unit on a storage device often use a power of 2 for simplification of processing. Before starting this procedure, the encryption speed, the decryption speed, the time required to generate a record encryption key, and the time required to generate initialization data are determined.

In FIG. 21, first, the average value of the access length recorded in the access information storage unit 125 is obtained (step 2102). Here, “14” is used as the average access length.
It is assumed that "0" bytes have been obtained. Next, the smallest power of 2 exceeding the average access length is obtained (step 2102). In this example, it is "256".

Subsequently, suppose that the record lengths are 1, 2, 4,
, And the following procedure is performed as a power of 2 to obtain an average write overhead time in each case (step 2103). The upper limit of the tentative record length is the smallest power of 2 exceeding the average access length, obtained in the previous procedure. In this example, it is "256".

The calculation performed for each temporary record length is as follows. First, the average of the lengths required for re-encryption processing at the time of writing and the average number of calculations of the record encryption key and the initialization data for one access are obtained. The length required for the re-encryption process is the portion as shown in FIG. The average re-encryption processing length is
This is the average value of the values obtained by the equation shown in “Equation 1” for each access length.

[0058]

(Equation 1)

The average number of times of calculation is the average value of the values obtained by the equation shown in "Equation 2" for each set of the access position and the access length. The meanings of the symbols used in "Equation 1" and "Equation 2" are as shown in FIG. In addition, "L%
“R” means “the remainder of L / R”.

[0060]

(Equation 2)

Next, the average re-encryption processing length and the average number of calculations obtained as described above, the encryption processing speed, the decryption processing speed, the time required to generate the record encryption key, and the generation of the initialization data "Time 1", "Time 2"
The average write overhead time when the temporary record length used in the calculation of (1) is used can be obtained by using the equation shown in “Equation 3”.

[0062]

(Equation 3)

Here, (average re-encryption processing length) / (decryption speed) in "Equation 3" is the average of the time required to decrypt the portion read from the file and requiring re-encryption processing. It is. (Average re-encryption processing length) / (encryption speed) is the average of the time required to encrypt the portion that requires re-encryption processing. ｛...｝ (average number of calculations) is the average of the time required to calculate the record key prepared for each record and the initialization data. These three
The sum of the two equations is the average of the write overhead time.

The temporary record length giving the minimum value is selected from the average write overhead times obtained for the respective temporary record lengths (step 210).
4). This is the record length that minimizes the write overhead. Finally, the record size storage unit 1 combines the application program and the selected record length.
24 (step 2105).

As described above, in this embodiment, the data read / write request to the storage device 111 issued from the application program 106 of the terminal 101 to the operating system 108 is intercepted, and the data is encrypted when the write request is issued. An encryption key for performing encryption is obtained from the key management server 112 connected via the network 122, and the data is encrypted with the encryption key and stored in the storage device 11.
1, and when a read request is made, the storage device 11
1 to obtain a key for decrypting the encrypted data from the key management server 112, decrypt the encrypted data with the encryption key, and pass the extracted data to the application program 106. As a result, the data to be stored in the storage device 111 can be automatically encrypted without explicitly instructing the user to perform encryption or decryption, and can be automatically decrypted when read out, forcing the user to perform a troublesome operation. The effect that there is not is obtained. Further, since the data to be stored in the storage device 111 is automatically stored, there is no problem that the user forgets to encrypt the data.

Before issuing a request to the key management server 1112 to send an encryption key, the user operating the application program 106 is required to input information for identifying the user. The user's key is retrieved from the key management server 112 after confirming the correctness of the terminal 101 operated by the user, or the identification information input by the user is sent to the key management server 112, and the identification received by the key management server 112 is received. Since the user's encryption key is sent back after confirming the correctness of the information, even if the portable terminal storing the encrypted confidential data is stolen, the danger of decryption is limited to these. The data is smaller than when the data is stored in the same storage device, and the confidentiality of the data can be further increased. For example, if you store encrypted data on a portable terminal and want to access the data in-house,
N, if the user accesses the company network remotely from outside the company, the user who illegally obtains the portable terminal can not only guess the user's identification information but also use the user at the time of remote access. Since the certification work also needs to be performed, the security is higher. In-house, a portable terminal can be connected to the same network as the key management server so that important data can be edited and viewed.
Since there is no key management server outside the company, it can be configured so that the data cannot be accessed, and the security can be enhanced.

Further, the application program 10
The mechanism for intercepting a data read / write request from the OS 6 to the operating system 108 is as follows.
There is no need to rewrite existing application programs or operating systems, and there is no need to replace hardware, and data security can be increased with minimal cost. further,
A method of recording a user-specific encryption key on an IC card and managing the encryption key by each user himself is also conceivable.
Data loss becomes impossible due to loss of the C card itself, and it is necessary to add an IC card read / write mechanism to the terminal 101, which is disadvantageous in terms of cost. However, by obtaining the encryption key from the key management server 112 as in the present embodiment, there is an advantage that a terminal having no IC card read / write mechanism can be used.

In this embodiment, when encrypting a file, a file encryption key is generated each time without using a user key as it is. However, the file itself may be directly encrypted with a user key. In addition, every time a file is saved or read, the user is required to input a user name and a password. However, such information is temporarily stored in the memory of the terminal 101, and the information is stored in the next file saving and reading. By using the temporarily stored user name and password to generate a key management request, the user's input operation can be further simplified. Further, by temporarily storing the obtained user key itself in a memory and reusing it later, the terminal 10
1 and the key management server 112 need not be performed, so that the processing speed can be increased by eliminating the communication overhead, and the traffic on the network 122 can be reduced.

In addition, when the user saves a file in advance, the user can automatically specify a file or a directory to be encrypted, so that only the specified file or a file under the specified directory can be specified. It can perform encryption and decryption. This allows
You can also specify a directory that represents a storage medium such as a floppy disk as a place to store the encrypted data.
It is also possible to prevent important information from being copied and taken out.

Further, the terminal 101 and the key management server 1
In FIG. 12, each functional part that realizes the function described in the embodiment is specifically configured by processing programs that realize equivalent functions, and these processing programs are stored in a storage medium such as a CDROM. Or through a communication medium such as the Internet.

In this embodiment, the encryption key and the initialization data are calculated for each record. However, the file encryption key and the file initialization data may be used as they are in order to increase the reading / writing speed. . In this case, the security of the encrypted file is slightly lost compared to the present embodiment. Also, the method of calculating the record length needs to be changed.

In order to determine the record length, not only the access length of the application but also the unit of cache for file access by the operating system or the unit of recording data (for example, sector length) on the storage device can be used. In addition, when the record length is obtained, the average write time is obtained by using both the read and write access records. However, the calculation may be performed by strictly distinguishing between the read and write. For this purpose, a column for distinguishing between reading and writing may be provided in the access information storage unit. Further, the record length may be calculated not only when the record length for the application program is not determined, but also periodically, for example, once a week.

When the record length is found to be different from the record length used so far, the existing file may be re-encrypted. By providing an area for storing the record length in the encrypted file, the record length when encrypting the file can be stored. In this way, when the optimum record length for the application program changes, the existing encrypted file can be easily re-encrypted using the new record length value.

[0074]

As described above, according to the present invention, data to be stored in a storage device is automatically encrypted without a user explicitly giving an instruction for encryption or decryption, and automatically read and read. The decryption can be performed, and an effect that the user does not have to perform a troublesome operation can be obtained. Further, since the data to be stored in the storage device is automatically stored, there is no problem that the user forgets to encrypt the data.

Also, the overhead of re-encryption processing and initialization data generation processing at the time of data overwriting, which is a problem when automatically encrypting / decrypting data, can be minimized. The data overwriting process can be sped up as compared with the case.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing an embodiment of a computer system to which the present invention has been applied.

FIG. 2 is a configuration diagram of a key information record distributed to a user.

FIG. 3 is a flowchart showing a procedure for creating user distribution information.

FIG. 4 is a configuration diagram of an authentication token.

FIG. 5 is a flowchart showing a file encryption procedure.

FIG. 6 is a diagram showing a format configuration of a message transmitted and received between a terminal and a key management server.

FIG. 7 is a diagram showing original contents included in a user key request message data part.

FIG. 8 is a configuration diagram of a user key request message.

FIG. 9 is a diagram showing original contents (with a user key) included in a user key reply message data part.

FIG. 10 is a diagram showing original contents (without a user key) included in a user key reply message data part.

FIG. 11 is a configuration diagram of an encrypted file stored in a storage device.

FIG. 12 is a flowchart showing a file decryption procedure.

FIG. 13 is a flowchart illustrating a processing procedure of a key management application.

FIG. 14 is a flowchart showing a detailed procedure of encryption.

FIG. 15 is a configuration diagram of a write request from an application program.

FIG. 16 is a diagram illustrating a record size storage unit.

FIG. 17 is a diagram illustrating an access information storage unit.

FIG. 18 is a diagram illustrating a range overwritten on a file by execution of a write request and a range requiring re-encryption processing.

FIG. 19 is a flowchart showing a detailed procedure of decoding.

FIG. 20 is a configuration diagram of a read request from an application program.

FIG. 21 is a flowchart showing a procedure for obtaining a record length.

FIG. 22 is an explanatory diagram of symbols used in calculation formulas.

[Explanation of symbols]

101 terminal, 102 user input unit, 103 password encryption key generation unit, 104 file encryption key generation unit, 1
05: encryption / decryption unit, 106: application,
107: File access hook unit, 108: Operating system, 109: Storage device interface, 110: Communication interface, 111: Storage device, 112: Key management server, 113: Key management application, 114: User input unit, 115 ... Password encryption key generation unit, 116: user key generation unit, 117: encryption / decryption unit, 118: operating system, 11
9: Communication interface, 120: Storage device interface, 121: Key database, 122: Network, 123: User, 124: Record size storage unit, 125: Access information storage unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference)

Claims (9)

[Claims] 1. An application program comprising: a storage device; and a computer having file hook means for intercepting a data read / write request from the application program to the storage device, and executing a process according to the application program. In the data storage method of writing and storing the processed data in the storage device, in response to a data write request from the application program, the write request is intercepted by the file hook means, and the operating system determines that the write target is the write target. Before writing the data to the storage device, the data is encrypted in a record length unit set in advance using an encryption key stored in an internal memory of the computer, and written to the storage device. The read request is intercepted by the file hook means, and before the read data is transferred to the application program, the operating system reads the encrypted data from the storage device in record units. And outputting the decrypted data to the application program that has issued the read request by decrypting the encrypted data with a predetermined record length unit using the encryption key stored in the internal memory. How to save data. 2. The storage device according to claim 1, wherein only data in a file designated by a user in advance or data of all files in a designated directory is encrypted or decrypted. 2. The data storage method according to claim 1, wherein: 3. The data storage method according to claim 2, wherein the record length unit is set for each application program. 4. Record access information at the time of file access by an application program, set a temporary record length exceeding an average access length calculated based on the access information, and calculate an overhead time for each temporary record length. 3. The data storage method according to claim 2, wherein the record length whose calculation result is the minimum is set as the record length. 5. The data storage method according to claim 2, wherein the record length is a cache unit when a file is accessed by an operating system. 6. The data storage method according to claim 2, wherein the record length is a data recording unit in a storage device. 7. The data storage method according to claim 2, wherein the encryption key is obtained from a key management computer when authenticating a user who operates the computer. 8. The first encryption key acquired from a key management computer at the time of authentication of a user who operates the computer.
Encryption key, and when encrypting the data to be stored,
An encryption encryption key is created by encrypting a second encryption key generated inside the computer using the first encryption key, and an encrypted data body obtained by encrypting data to be written using the first encryption key is generated. The encrypted encryption key is added to the encrypted data body and written to the storage device, and upon decryption, the encrypted encryption key is decrypted with the first encryption key, and the decryption key obtained by decryption is obtained. 7. The data storage method according to claim 2, wherein the encrypted data body is decrypted using the second encryption key. 9. A computer system having a computer that executes a process according to an application program and a storage device connected to the computer, for writing and storing data processed by the application program in the storage device. A recording medium on which a data storage processing program is recorded, wherein a file hook process for intercepting a data read / write request to the storage device issued from the application program to an operating system of the computer, and data from the application program In response to the write request, the file request is intercepted by the file hook means, and before the operating system writes the data to be written to the storage device, A first process of encrypting data in a record length unit set in advance using an encryption key stored in an internal memory of the computer and writing the encrypted data to the storage device; and in response to a read request from the application program, the read request is sent to the file hook. Before the data is intercepted by the means and before the read data is transferred to the application program, the operating system reads the encrypted data from the storage device in units of records, and then uses the encryption key stored in the internal memory to read the encrypted data. A second process of decrypting the encrypted data in units of a record length set in advance, and transferring the decrypted data to the application program which has issued the read request; Recording medium for data storage processing .