JP5631251B2 - Information leakage prevention method - Google Patents

Description

  The present invention can edit confidential information that has been taken out to a third party outside the organization even if it is necessary to take it out and edit it. The present invention relates to an information leakage prevention method and system.

According to the Personal Information Protection Law, information leakage countermeasures are an important issue for organizations such as companies.
As a countermeasure, information that should not be leaked outside the company is basically prohibited to be stored on removable media or portable computers and taken outside the company. If it is unavoidably taken, it must be encrypted. A system designed to do this has been developed.
However, even if the encrypted information is taken out, for example, if the confidential information read from the removable medium is misplaced in the personal computer of the hotel on a business trip, there is a risk that the confidential information may be leaked.
Therefore, the information stored in the removable media is automatically encrypted using a special encryption algorithm, and the confidential information read and edited from the removable media can be stored only in the removable media. A system has been proposed (see Patent Document 1).

According to the above system, even if the removable medium itself is lost, the confidential information is encrypted by an encryption algorithm unique to the removable medium, and the confidential information read from the removable medium For example, even if editing is performed on a personal computer at a hotel, there is no risk of leaving confidential information on the personal computer and leaking it to a third party. Further, since password authentication is performed when opening an encrypted document file stored in a USB memory, the encrypted document file cannot be opened even if the removable medium is lost. Furthermore, since the organization key authentication is performed, it is possible to prevent the decryption program from being activated on a medium other than the removable medium authenticated by the organization, and prevent a plain text document from being stored and leaked on a computer outside the organization.

  However, in Patent Document 1, there is no processing for deleting a decryption program copied from a removable medium, a plaintext of confidential information decrypted in the hard disk, or a plaintext of a document file newly stored as confidential information. Therefore, there is a risk that data remains in the used environment, and confidential information is leaked from a used computer to a third party.

  An object of the present invention is to provide a technique for deleting a decryption program copied from a removable medium and a plaintext of confidential information remaining in a hard disk after using the removable medium.

In order to achieve the above object, the present invention creates a removable medium storing a decryption program for encrypted confidential information in which an organization key unique to an organization having jurisdiction over confidential information is embedded, and stores the decrypted information stored in the removable medium. When the program is incorporated into a computer in the organization, the organization authentication server authenticates whether the organization key embedded in the decryption program corresponds to the organization key unique to the organization, and the organization key is unique to the organization. A first step of permitting incorporation of the decryption program only when corresponding to an organization key;
When starting the decryption program incorporated in a computer in the organization, the organization authentication server authenticates whether the organization key embedded in the decryption program corresponds to an organization key unique to the organization, and the organization key In the information leakage prevention method, comprising: a second step of starting the decryption program only when the key corresponds to an organization key specific to the organization,
At the time of the saving operation after the editing processing of the plaintext of the confidential information decrypted by the activated decryption program in the computer, the plaintext to be saved is encrypted and saved in the removable medium, and the saving target is saved from within the computer. A third step of deleting the plaintext, a fourth step of deleting the decryption program incorporated in the computer in the organization from the removable medium upon removal of the removable medium, and deleting the decryption program A fifth step of collecting environmental information such as a Mac address and an IP address of the computer in the organization in which the decryption program was incorporated at the time, and storing it in the removable medium, and a removable medium storing the environmental information Before decryption program embedded in When installing in a computer in an organization, the environment information of the computer and the environment information stored in the removable medium are compared to match, and if they match, the organization key is authenticated by the authentication server And a sixth step of permitting the incorporation of the decryption program .

  According to the present invention, the decryption program copied after the use of the removable medium and the plaintext of the confidential information decrypted in the hard disk of the computer are surely deleted, so that the confidential information is leaked from the environment after being used once. Can be prevented.

It is a system configuration figure showing an embodiment of an information system to which the present invention is applied. It is a block diagram which shows the outline | summary of the client computer in an organization. It is a block diagram which shows the outline | summary of the client computer outside an organization. It is a functional block diagram which shows the structure of the USB memory used as a removable medium. It is a block diagram which shows the outline | summary of the authentication server in an organization. It is a figure which shows the example which encrypts and takes out a document with USB memory. It is a figure which shows the utilization form which edits the document taken out by USB memory with a home computer. It is a figure which copies the decoding program from USB memory to a client computer, and shows the utilization form of the copied decoding program. It is a figure which shows the opportunity which records the document operation history using a USB memory. It is a figure which shows the opportunity which records the decoding log | history using USB memory. It is a figure which shows deletion of the copied decoding program It is a flowchart which shows the procedure which copies a decoding program to a client computer by the decoding program copy tool preserve | saved at USB memory. It is a flowchart which shows the procedure which decodes an encryption document file by a decoding program. It is a flowchart which shows the procedure which encrypts and preserve | saves the document in USB memory, and decodes an encrypted document so that edit is possible. It is a flowchart which shows the continuation of FIG. It is a flowchart which shows the procedure which deletes the plaintext document file and decryption program which were decrypted when extracting the USB memory. It is a flowchart which shows the procedure in the case of installing a decoding program in the same machine. It is a figure explaining that a file operation menu is changed when an encrypted document is decrypted by a document operation control program in a USB memory. It is a figure which shows the example of the file operation menu displayed when decoding an encrypted document with a decoding program.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a system configuration diagram showing an embodiment of an information system to which the present invention is applied. When starting up client computers 12 to 14 in an organization, each client computer is a legitimate computer belonging to the organization. There is an authentication server 11 that authenticates whether there is any.
The users of the client computers 12 to 14 store the confidential information in the USB memory 15 which is a removable medium as needed and take it out of the organization, and then use the client computer 16 (for example, a home computer) 16 Edit work can be done.

FIG. 2 is a block diagram showing an outline of the internal configuration of the client computers 12 to 14 in the organization, which includes a keyboard 21, a mouse 22, a display 23, a CPU 24, and a hard disk 25, and a document creation program 251 in the hard disk 25. An information input / output monitoring program 252 and a decryption program 253 are stored.
The document creation program 251 has functions such as document and spreadsheet.
The information input / output monitoring program 252 monitors the take-out of confidential information. According to the security policy of the organization, the information input / output monitoring program 252 sets functions such as storage restraint to removable media, print restraint, and screen copy restraint. Prevent external leakage.
The decryption program 253 is a copy of the decryption program stored in advance in the USB memory 15, and only when the organization key embedded in the decryption program in the USB memory 15 corresponds to the organization key managed by the authentication server 11. Copied from the USB memory 15 to the hard disk 25.
When copied, the hard disk attributes (for example, serial number, cylinder configuration, etc.) 2531, organization key 2532, password 2533, and device attribute 2534 of the USB memory 15 of the copy source are embedded, and can only be activated by the copied computer. To be done. The decryption program 253 includes an authentication process 2535 for receiving authentication by the authentication server 11 upon activation and a decryption history recording process 2536 for recording a decryption history.
The client computers 12 to 14 are provided with a USB port for inputting / outputting data to / from the USB memory 15.

  FIG. 3 is a block diagram showing an outline of the internal configuration of the client computer 16 outside the organization, which includes a keyboard 31, a mouse 32, a display 33, a CPU 34, and a hard disk 35. A document creation program 351 is stored in the hard disk 35. Has been. A USB port for inputting / outputting data to / from the USB memory 15 is also provided.

FIG. 4 is a functional block diagram showing an internal configuration of the USB memory 15 used when taking confidential information in the organization to the outside as necessary. The USB memory 15 includes a first storage area 41 and a second storage area 42. The first storage area 41 stores a document operation control program 411, a decryption program 412, a decryption program copy tool 413, and a decryption program deletion program 415. In addition, the encrypted document file 421 is stored in the second storage area 42.
The document operation control program 411 has a function of encrypting confidential information stored in the USB memory 15 and a function of decrypting stored confidential information, and further records an operation history record of the document in an encrypted log file 414. Has processing. Also, a decrypted document deletion process 4115 for deleting the decrypted document file is provided.
For example, when the USB memory 15 is attached to the client computer 12 and the encrypted document file 421 stored in the second storage area 42 is edited, the document operation control program 411 once decrypts the encrypted document file 421. Then, the contents of the decrypted plain text document file are displayed on the document editing screen of the document creation program 251. At this time, the displayed document contents cannot be saved or printed with a different file name. Change the menu on the document edit screen.

That is, the file operation menu on the document editing screen of the document creation program 251 usually has a new creation, opening, closing, overwriting, saving as a name, printing, as illustrated in FIG. When there is a menu item such as “end”, the document operation control program 411 displays the contents of the decrypted plain text document file on the document editing screen of the document creation program 251, and displays the menu item of the file operation menu as shown in FIG. ), The menu items such as import, open, close, delete, save to USB memory, and exit are changed. In order to prevent the displayed document content from being saved with a different file name or to be printed, only the USB memory 15 can be specified as the storage destination of the edited document content, and the edited document content is designated as the document. The data is encrypted with an encryption algorithm unique to the operation control program 411 and stored in the second storage area 42. In addition, the decrypted document file can be manually deleted.
Further, the device operation attribute (for example, serial number, version, number of cylinders, etc.) 4112 of the USB memory 15 is embedded in the document operation control program 411, and decrypted with respect to another USB memory whose device attributes do not match. The document contents cannot be saved.
Further, a password 4113 and an organization key 4114 for starting the document operation control program 411 are embedded, and when the password input by the user does not match the password 4113, it is not started. Thereby, even if the USB memory 15 itself is lost, there is no risk of the stored encrypted document file 421 leaking outside.

The decryption program 412 is used by being copied to the client computers 12 to 14 in the organization by the decryption program copy tool 413, and the encrypted document file 421 can be decrypted in the copy destination computer and stored in the hard disk. It is to make.
The decryption program 412 includes an authentication process (corresponding to 2535 in FIG. 2) and a decryption history recording process (corresponding to 2536 in FIG. 2) for receiving authentication by the authentication server 11 when activated.
The device attribute 4112 embedded in the document operation control program 411 in the same USB memory 15 so that the encrypted document file 421 encrypted by the document operation control program 411 in the other USB memory 15 cannot be decrypted. The same device attribute 4123 is embedded.
Furthermore, when the password 4124 and the organization key 4125 for starting the decryption program 412 are embedded, and the password and organization key input by the user do not match the password 4322 and the organization key 4323, the password 4124 and the organization key 4323 are not activated. Yes.
As a result, the encrypted document file 421 stored in another USB memory having a different organization key cannot be decrypted.

Similarly, in the decryption program copy tool 413, the same device attribute 4131 as the device attribute 4112 embedded in the document operation control program 411 in the same USB memory 15 is embedded. Further, when the password 4132 and the organization key 4133 for starting the decryption program copy tool 413 are embedded, and the password and organization key input by the user do not match the password 4132 and the organization key 4133, it is time to start up. It is impossible and cannot be copied to client computers outside the organization.
The device attributes, passwords, and organization keys embedded in the programs 411, 412, and 413 are all encrypted with an encryption key unique to the USB memory 15.
The decryption program copy tool 413 also includes a copy history storage process 4134 for recording the decryption program copy history in the copy log file 4136. The copy log file 4136 is also used by the decryption program deletion program 415.

FIG. 5 is a block diagram showing an outline of the internal configuration of the authentication server 11, which includes a keyboard 51, a mouse 52, a display 53, a CPU 54, a hard disk 55, and a memory 56, and the client computer 12 in the organization is included in the memory 56. An authentication program 561 for authenticating whether the user Nos. To 14 is a valid user and whether the USB memory 15 is a valid USB memory certified in the organization is stored.
This authentication process is performed based on the organization key and user password stored in the hard disk 55.

FIGS. 6 to 8 are diagrams showing examples of usage forms when confidential information is taken out and edited by the USB memory 15 and the edited confidential information is decrypted and used by a client computer in the organization.
FIG. 6 is a diagram showing a case where the document 61 created by the document creation program 251 of the client computer 12 in the organization is stored in the USB memory 15 and taken out.
When the document 61 is stored in the USB memory 15 and taken out, the USB memory 15 is attached to the USB port of the client computer 12 in the organization, the document operation control program 411 in the USB memory 15 is activated, and the document operation control program 411 is installed. The document 61 to be taken out is selected by the menu operation and is taken into the USB memory 15. Then, by the menu operation, the captured document 61 is encrypted and stored as an encrypted document in the second storage area 42 of the USB memory 15.
The stored encrypted document 62 is attached to the USB port of the other client computers 13 and 14 in the organization and the client computer 16 outside the organization, and the document operation control program 411 is started to thereby control the document operation. The program 411 can be decrypted and edited by the decryption function. However, the storage destination of the edited document is limited to the USB memory 15.

FIG. 7 is a diagram showing an example in which a document 73 created by the client computer 12 inside the organization and encrypted and stored in the USB memory 15 is edited by the client computer 16 at home outside the organization.
When the encrypted document 73 is edited by the client computer 16 at home outside the organization, the USB memory 15 is attached to the USB port of the client computer 16 at home, and the document operation control program 411 in the USB memory 15 is started up. The encrypted document 73 to be edited is selected by the menu operation of the operation control program 411, is decrypted by the decryption function of the document operation control program 411, and the document creation program 351 of the home client computer 16 is started by the document operation control program 411. The decrypted document content is expanded in the document editing screen of the document creation program 351 so that it can be edited.
The storage destination of the edited document is limited to the USB memory 15 and cannot be stored as the document 72 in the client computer 16 at home.
The document 71 created by the client computer 16 at home can be encrypted, stored in the USB memory 15 and taken out, and edited by the client computers 12 to 14 in the organization.

FIG. 8 is a diagram showing an example in which the encrypted document stored in the USB memory 15 is decrypted and stored in the hard disk of the client computer 12 in the organization.
First, as shown in FIG. 8A, the decryption program copy tool 413 stored in the USB memory 15 is activated to copy the decryption program 412 to the client computer 12 in the organization. At this time, the copy history is stored in the copy log file 4136 by the copy history recording process 4134.
In this copy operation, authentication of the password and the organization key is performed in the authentication server 11, and copying is permitted only when a valid password and organization key are input.
The copied decryption program 412 is embedded with the attributes of the hard disk 25 that is the copy destination (corresponding to 2531 in FIG. 2), the organization key 4133, the password 4132, and the device attributes 4131 (2532, 2533, and 2534 in FIG. 2). Is incorporated by the decryption program copy tool 413.
When the encrypted document 82 in the USB memory 15 is decrypted and stored in the hard disk of the client computer 12 in the organization, the copied decryption program 412 is activated to display a screen 1601 as shown in FIG. “Open encrypted file” is selected from the middle file menu, the encrypted document 82 to be decrypted is designated, and the decrypted program 412 decrypts it as a plain text document 81 (FIG. 8B).
Even when the decryption program 412 is activated, authentication of the password and the organization key is performed by the authentication server 11, and decryption is permitted only when a valid password and organization key are input.

  FIG. 9A is a diagram illustrating an example in which a history of document operations (document editing and saving operations) by the document operation control program 411 is recorded. When the document 91 in the client computer 12 in the organization is opened by the document operation control program 411 in the USB memory 15 and stored as the encrypted document 92, the operation history is input / output to / from the client computer 12 in the organization. The document is transmitted to the monitoring program 252, and the document entry / exit using the USB memory 15 is centrally managed.

  FIG. 9B is a diagram showing an example of recording a history when the document 93 in the client computer 16 at home is operated by the document operation control program 411 in the USB memory 15. When the document operation control program 411 in the USB memory 15 opens the document 93 in the client computer 16 at home and when the document 93 is saved as the encrypted document 94, the operation is recorded by the operation history recording process 4111 in the document operation control program 411. An operation history is stored in the log file 414.

  FIG. 10A shows an information input / output monitoring program 252 that records the operation history recorded in the encryption log file 414 of the USB memory 15 when the decryption program 412 copied to the client computer 12 in the organization is started. It is a figure which shows the example which transmits to and records. When the decryption program 412 is activated, the decryption program 412 reads the operation history recorded in the encryption log file 414 in the USB memory 15 and transmits it to the information input / output monitoring program 272. Thereafter, the operation history information in the encrypted log file 414 is deleted.

  FIG. 10B shows that when the decryption program 412 copied to the client computer 12 in the organization is activated to decrypt the encrypted document 101 in the USB memory 15, the decryption history is stored in the information input / output monitoring program 252. It is a figure which shows the example which transmits and records. When the decryption program 412 decrypts the encrypted document 101 as the plain text document 102, the operation history is transmitted to the information input / output monitoring program 252 so that the information input / output monitoring program 252 collectively manages the operation history.

FIG. 11 is a diagram showing an example of deleting the decryption program copied to the client computer 12 in the organization when the USB memory 15 is pulled out.
The decryption program deletion program 415 reads history information from the copy log file 4136 in the USB memory 15 and deletes the copied decryption program.
FIG. 12 is a flowchart showing the processing of the decryption program copy tool 413 for copying the decryption program 412 in the USB memory 15 to the client computers 12 to 14 in the organization.
When copying the decryption program 412 to the client computer 12 in the organization, the decryption program copy tool 413 is activated after the USB memory 15 is attached to the USB port of the client computer 12.
The activated decryption program copy tool 413 first prompts the user to input a password in order to confirm whether the user has a right to use the program in the USB memory 15.
If the password is input by the user, the password is accepted, and the password is authenticated depending on whether or not it matches the password 4132 embedded in the decryption program copy tool 413 (steps 1201 and 1202). After the authentication is successful, the organization key 4133 embedded in the decryption program copy tool 413 is read, and an authentication request for the organization key 4133 is transmitted to the authentication server 11 (step 1203).
Since the organization key used in the organization is stored in the database 55 of the authentication server 11, the authentication server 11 uses the organization key 4133 sent from the decryption program copy tool 413 and the organization key stored in the database 55. The organization key 4133 is authenticated depending on whether or not the two match, and the result is returned to the decryption program copy tool 413.

FIG. 13 is a flowchart showing the processing of the decryption program.
When the authentication result from the authentication server 11 is “authentication successful” (step 1204), the decryption program copy tool 413 receives the designation of the copy destination of the decryption program 412 in the client computer 12 from the user (step 1205). The decryption program 412 is copied to the designated copy destination (step 1206).
Thereafter, as described with reference to FIG. 8, the copy history is saved (step 1207), and the hard disk attribute 2531 of the copy destination and organization key 2532 (same as 4333) for the decryption program 253 copied as shown in FIG. And a password 2533 (same as 4332) and a device attribute 2534 (same as 4331) are embedded (step 1208).
If password authentication and organization key authentication are not successful, an error is displayed (step 1208) and the decryption program 412 is not copied.

FIG. 13 is a flowchart showing the processing of the decryption program 253 when the decryption program 253 copied to the client computer 12 in the organization is activated to decrypt the encrypted document in the USB memory 15.
When decrypting the encrypted document in the USB memory 15, the decryption program 253 copied to the client computer 12 in the organization is activated.
The activated decryption program 253 prompts the user to input a password in order to confirm whether the user has the proper authority to use the decryption program 253.
If the password is input by the user, the password is accepted and the password is authenticated depending on whether or not it matches the password 2533 embedded in the decryption program 253 (steps 1301 and 1302). After the success, the organization key 2532 embedded in the decryption program 253 is read, and an authentication request for this organization key 2532 is transmitted to the authentication server 11 (step 1303).
Since the organization key used in the organization is stored in the database 55 of the authentication server 11, the organization key 2532 sent from the decryption program 253 matches the organization key stored in the database 55. The organization key 2532 is authenticated depending on whether or not to do so, and the result is returned to the decryption program 253.

When the authentication result from the authentication server 11 is “authentication successful” (step 1304), the decryption program 253 determines the device attribute of the document operation program 411 paired with the decryption program 412 that is the copy source of the decryption program 253. And the device attribute 2534 embedded in the decryption program 253 are determined to be the same (step 1305). If they are not the same, a USB memory with another device attribute is attached, so an error is displayed ( Step 1312), the process is terminated.
However, if the device attributes match, it is determined that the valid USB memory 15 that is the copy source of the decryption program 253 is installed, and then the hard disk embedded in the decryption program 253 It is determined whether or not the attribute 2531 matches the hard disk attribute of the client computer (step 1306). If the attribute 2531 is not the same, it is determined that the attribute 2531 has been illegally copied on another hard disk, and an error is displayed ( Step 1312), the process is terminated.
However, if the hard disk attributes are the same, the document operation history information stored in the encrypted log file 414 in the USB memory 15 is then collected as described with reference to FIG. The operation history information of the collection source encrypted log file 414 is deleted (step 1307), and the collected operation history information is transmitted to the authentication server 11 (step 1308).

Next, a screen 1901 as shown in FIG. 19 is displayed on the display 23 of the client computer 12, and designation of the name of the encrypted document file to be decrypted is accepted from “Open encrypted file” in the file menu (step 1309). The designated encrypted document file is decrypted (step 1310).
Thereafter, as described in FIG. 10B, an operation history indicating that the encrypted document file has been decrypted is transmitted to the authentication server 11 (step 1311).
The plain text document decrypted by the decryption program 253 can be stored in the hard disk and can be arbitrarily edited by the document creation program 251.

FIG. 14 and FIG. 15 are flowcharts showing a procedure when a plain text document is encrypted and stored in the USB memory 15 by the document operation control program 411 in the USB memory 15 or an encrypted document file is decrypted and edited. It is.
First, after the USB memory 15 is attached to the USB port of the client computer 12 in the organization, the document operation control program 411 in the USB memory 15 is activated.
The activated document operation control program 411 first prompts the user to input a password in order to confirm whether the user has a proper use authority for the document operation control program 411.
If the password is input by the user, the password is accepted and the password is authenticated depending on whether or not it matches the password 4113 embedded in the document operation control program 411 (steps 1401 and 1402). After the authentication is successful, the device attribute 4112 embedded in the document operation control program 411 is read, and it is checked whether the device attribute 4112 and the device attribute set as the unique information in the USB memory 15 are the same (step 1403), if they are not the same, the document control program 411 recognizes that the copy was illegally copied from another USB memory, displays an error (step 1407), and ends the process.

However, if the device attributes are the same, the device is recognized as a valid USB memory, and then the organization key 4314 embedded in the document operation control program 411 is read, and an authentication request for the organization key 4114 is issued. It transmits to the authentication server 11 (step 1404).
Since the organization key used in the organization is stored in the database 55 of the authentication server 11, the authentication server 11 receives the organization key 4114 sent from the document operation control program 411 and the organization key stored in the database 55. The organization key 4114 is authenticated depending on whether or not the two match, and the result is returned to the document operation control program 411.
If the authentication result from the authentication server 11 is “authentication successful” (step 1405), the document operation control program 411 recognizes that the client computer equipped with the USB memory 15 is a client computer in the organization, and so on. If not, it is recognized that the client computer is outside the organization.
In response to these authorization results, the file menu when the encrypted document file is opened is changed. In other words, change the file operation menu item so that copy to clipboard, screen copy to clipboard, print suppression, and macro function suppression are possible, and the menu item should be changed so that the save destination is limited to USB memory. It adds (step 1406).
As a result, the encrypted document can be taken out by the USB memory 15.

Next, a file operation menu is displayed (step 1508), and an operation target menu is received (step 1509).
If the menu to be operated is reading of an encrypted file (step 1510), a list of encrypted document files in the USB memory 15 is acquired and displayed (step 1511), and the encrypted document file in the list is designated. Is received (step 1512). The designated encrypted document file is read from the USB memory 15 (step 1513), decrypted by the decryption function, and expanded and displayed on the document editing screen of the document creation program 251 in which the file operation menu item is changed (step 15). 1514).
Then, the operation history of the encrypted document file decrypted at this time is transmitted to the authentication server 11 (step 1515).

On the other hand, when the file operation menu selected by the user is a menu item for reading a plain text document file created by the document creation program 251 of the client computer 12 (step 1516), the designation operation of the plain text document file is accepted (step 1516). 1517) The designated plain text document file is read from the hard disk 25 (step 1518), and expanded and displayed on the document editing screen of the document creation program 251 in which the file operation menu item is changed (step 1519).
Then, the operation history of the document file displayed at this time is transmitted to the authentication server 11 (step 1520).
When the editing of the document displayed on the editing screen is finished and the user designates a save operation to the USB memory 15 (step 1521), the edited document is encrypted and stored in the USB memory 15 (step 1521). 1522). Then, operation history information related to the stored encrypted document file is transmitted to the authentication server 11 (step 1523). Thereafter, when file deletion in the client computer 12 that has been saved is selected (step 1524), the process is terminated after the file is deleted (step 1525).

In FIG. 15, a case has been described in which a USB memory is attached to the client computer 12 in the organization and the document is encrypted and saved, or the encrypted document is opened and edited. In addition, the USB memory 15 can be used in exactly the same procedure when a portable computer that is activated upon authentication by the authentication server 11 is taken out of the organization and the USB memory is used.
Further, even when the USB memory 15 is attached to the computer 16 outside the organization, only encrypted storage by the document operation control program 411 is permitted. For example, a document file created in-house is stored in the USB memory 15 and taken home. Even if editing is performed on a home computer, confidential information inside the company is not left behind on the home computer, and leakage of confidential information from the home computer can be prevented.

FIG. 16 is a flowchart showing a procedure for deleting the decryption program copied to the client computer 12 in the organization when the USB memory 15 is pulled out.
If the removal of the USB memory 15 is selected, the user is notified that the decryption program and the application for activating the data decrypted by the decryption program are to be executed before the removal process is executed and the USB memory 15 is installed. The MAC address, IP address, start date / time, and machine environment information of the client computer 12 are collected (step 1601).
Writing for storage in the USB memory into which each collected information is inserted (step 1602),
Next, it is confirmed whether or not the decryption program 412 and the activated application have been completed, and whether or not environment information has been saved in the USB memory (step 1603).
Next, a deletion program is activated from the USB memory (step 1604).
Next, the decryption program 412 is deleted from the client computer 12 in the organization by the deletion program (step 1605).
After the deletion process, the USB memory removal process is executed, and the process ends (step 1606).

FIG. 17 is a flowchart showing a process in a case where the decryption program is installed again and the environment is reconstructed in the environment once used.
First, the USB memory is inserted into the client (step 1701). Then, the environment information of the PC used in the past is called into the USB memory to be used and compared with the environment information of the inserted PC (step 1702).
If the environment information compared in step 1702 matches, the decryption program is installed without authentication (step 1703).
If it does not match the environment information, it is determined that no decryption program has been installed in the past,
The processing shifts to the processing in FIG.

As described above, in the present embodiment, confidential information in the organization is encrypted in the USB memory and allowed to be taken out, enabling external editing, and the storage destination of the edited document is stored in the USB memory. Because it is restricted and encrypted and saved, even if a document is edited on a computer outside the organization, confidential information will not be left in that computer, and confidential information will be leaked from a computer outside the organization. It can be prevented in advance.
Also, since password authentication and organization key authentication are performed when opening an encrypted document file stored in a USB memory, the encrypted document file cannot be opened even if the USB memory is lost, and the USB memory that has been authenticated by the organization Otherwise, the decryption program cannot be started, and it is possible to prevent a plain text document from being stored and leaked on a computer outside the organization.
In addition, the decryption program copied from the removable media and the plain text of the confidential information remaining on the hard disk are deleted after the removable media is used, preventing the confidential information from leaking to a third party from the environment in which it was used. can do.

DESCRIPTION OF SYMBOLS 11 Authentication server 12-14 Client computer in organization 15 USB memory 16 Client computer outside organization 251 Document creation program 252 Decryption program 2531 Hard disk attribute 2532 Organization key 2533 Password 2534 Device attribute 411 Document operation control program 412 Decryption program 413 Decryption program copy Tool 414 Encrypted log file 411 Encrypted document file

Claims (1)

When creating a removable medium storing a decryption program for encrypted confidential information in which an organization key unique to the organization having the confidential information is embedded, and incorporating the decryption program stored in the removable medium into a computer in the organization The authentication server of the organization authenticates whether the organization key embedded in the decryption program corresponds to the organization key specific to the organization, and only when the organization key corresponds to the organization key specific to the organization A first step of allowing incorporation;
When starting the decryption program incorporated in a computer in the organization, the organization authentication server authenticates whether the organization key embedded in the decryption program corresponds to an organization key unique to the organization, and the organization key In the information leakage prevention method, comprising: a second step of starting the decryption program only when the key corresponds to an organization key specific to the organization,
At the time of the saving operation after the editing processing of the plaintext of the confidential information decrypted by the activated decryption program in the computer, the plaintext to be saved is encrypted and saved in the removable medium, and the saving target is saved from within the computer. A third step of deleting the plaintext, a fourth step of deleting the decryption program incorporated in the computer in the organization from the removable medium upon removal of the removable medium, and deleting the decryption program A fifth step of collecting environmental information such as a Mac address and an IP address of the computer in the organization in which the decryption program was incorporated at the time, and storing it in the removable medium, and a removable medium storing the environmental information Before decryption program embedded in When installing in a computer in an organization, the environment information of the computer and the environment information stored in the removable medium are compared to match, and if they match, the organization key is authenticated by the authentication server And a sixth step of permitting incorporation of the decryption program .

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