JP2005065209A - Document security system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a document security system wherein convenience for users is enhanced. <P>SOLUTION: Disclosed is a document security system in a server/client structure including a document security server and user computers. A user eigen-key including the hardware information of a user computer is generated and stored in the document security server to be used for encrypting a document file downloaded from the document security server to the user computer. The encrypted document file includes a signature and a variable length header. The document file is encrypted for the unit of a block of 4 Kb. The document security server includes an event module for receiving and storing information on user actions to the document. The document security server includes a time synchronization module for providing a current time of the document security server associated with expiration for the use of the document file. License management is provided for the number of users and a supportable file extender. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a document security system in which authority is set for each user and document reading, storage, copying, and output are restricted to prevent document information from being leaked outside the company without permission. It is related with the document security system which improved the security and stability compared with the document security system of this, and improved the convenience of the user.

  Recently, many companies, public offices, schools, financial institutions, advanced technology research institutes, etc. use a knowledge management system (KMS) or an electronic document management system (EDMS). Manage internal document materials and improve the efficiency of business through information sharing.

  However, electronic document materials are attached in an irregular format and stored in a database, and users distribute it publicly and illegally in addition to using it for information sharing to improve business efficiency. Is the actual situation. Some of the materials shared by the knowledge management system can be shared in general. However, confidential materials inside and outside the research institute and main departments may be leaked due to inadvertent or intentional insiders. If this happens, it may cause a fatal loss to the company.

  As a conventional document security system for preventing such document leakage, an encryption algorithm is used for an original document stored in a knowledge management system or an electronic document management system (hereinafter referred to as a document management system). There is a document security system that can read, save, copy, and output according to a user authority policy (Access Control Logic) when a user is downloaded from an administrator.

  By such a document security system, it is possible to prevent the information from being used in the source in the case of illegal copying between users, prevention of external distribution, and outflow of materials through CD copying. Accordingly, confidential information such as IT company source code, advanced technology documents, business plans, drawings, accounting books, strategic plans, research papers, etc. is leaked out to propriety companies by proppy disc, CD, E-MAIL, etc. Block illegal activities such as

Such a conventional document security system is a copyright management system (DRM: Digital).
Designed based on the Rights Management) technology. DRM is a system technology that safely transmits various contents in a network from a provider (CP: Content Provider) to a customer (Client) and prevents the customer from illegally distributing the content.

  The most important technology in the DRM system is the encryption technology. Since information unique to the customer is used as an encryption key and the content or document is encrypted and transmitted, it can be copied and transmitted to a third party. This is a technology that prevents encryption from being decrypted. Of course, the DRM requires additional technologies such as a content usage rule control technology and a technology for billing settlement.

Briefly describing the above-described conventional document security system, the document security system includes a document security server and a server-client structure of each client computer. The document security server is composed of several service modules, and includes, for example, a key module for registering and managing user keys, a document encryption and distribution module for encrypting and distributing documents, and the like.

  The process performed in the conventional document security system will be briefly described. First, the user registers user-specific information and user key information in the document security server, which is stored in the user DB connected to the document security server. The The user selects and requests a document file to be downloaded to the document management system using a client program. In the document security server, information on the requested document file is communicated with the document management system, user information and authority are set, and the document file requester's PC uses the registered user key information. An encrypted document file that can only be viewed and used is generated, and the generated document file is transmitted to the user through the document management system. The user uses the corresponding document under conditions that are restricted by the set document use authority. The document file transmitted from the system to the user computer has an encrypted file format that is different from the original extension and is changed to a new extension. Through the document security agent program installed in the user computer Documents can be viewed and used.

The present invention relates to an improvement of the conventional document security system as described above, and the present invention improves the security and stability as compared with the conventional document security system, and improves the convenience of the user. The purpose is to provide an improved document security system.
The novel characteristic configuration of the present invention and the novel and inventive effect resulting therefrom will be described in detail in the specification to be described later.

  According to an aspect of the present invention, in the document security system, the present invention is connected to a user computer having a document security agent that generates a user-specific key, a document database in which the user computer and a document file are stored, and the user And registering the user unique key transmitted from the computer, encrypting the requested document file using the registered user unique key in response to a download request of the document file from the user computer, and A document security server for downloading to a computer, wherein the user specific key is generated using information extracted from hardware information of the user computer.

  Preferably, the module for extracting the user unique key is built in the document security agent.

  Preferably, the user unique key is transmitted from the user computer to the document security server in an encrypted form.

  Preferably, the encryption of the user unique key is based on a blowfish encryption algorithm.

  Preferably, prior to registration of the user-specific key in the document security server, it is checked whether or not the number of times that the user can be registered is exceeded through a license key attached to the document security server.

  Preferably, the license key is inserted into a USB key connected to a USB port of the document security server.

  Preferably, after the user unique key is registered, an environment file (Config File) including company code information of a company related to the document security server is transmitted from the document security server to the user computer and stored. The

  According to another aspect of the present invention, in the document security system, the present invention is connected to a user computer having a document security agent for generating a user-specific key, and a document database in which the user computer and the document file are stored, Registering the user unique key transmitted from the user computer, and in response to a request for downloading the document file from the user computer, encrypting the requested document file using the registered user unique key; A document security system including a document security server downloaded to a user computer, wherein the encrypted document file includes a variable length header including authority setting information for controlling authority of the user to the document. .

  Preferably, the authority for the document includes one or more of a viewing authority, an editing authority, a saving authority, an output authority, and an expiration date related authority.

  Preferably, the variable length header includes a dummy field having an arbitrary size.

  Preferably, the encrypted document file includes a signature indicating that the document file is an encrypted file.

  Also preferably, the signature is not encrypted.

  Preferably, the document file is encrypted by being divided into blocks of 4 kilobytes (Kbytes).

  Preferably, the document file stored in the document database is encrypted and stored.

  Preferably, the document file is encrypted using the user-specific key, and at the same time, a watermark including copyright holder information is embedded in the document file.

  Preferably, the document file is encrypted using the user unique key, and at the same time, a fingerprint including information for a valid user is embedded in the document file.

  Preferably, the document security server checks whether the requested document file is a document file having an extension supported by the system through a license file prior to encryption of the document file.

According to still another aspect of the present invention, in the document security system, the present invention is connected to a user computer having a document security agent for generating a user-specific key and a document database in which the user computer and the document file are stored. Registering a user-specific key transmitted from the user computer, and in response to a download request for the document file from the user computer, encrypting the requested document file using the registered user-specific key; A document security server to be downloaded to the user computer, and a document security agent of the user computer transmits user action information on the downloaded document to an event module included in the document security server, and the event module Action information of the user for transmitted the document provides a document security system is stored in the document security server and the connection event database.

  Preferably, the user action on the document includes one or more of a document browsing action, a saving action, an editing action, and an output action.

  Preferably, when the network connection for transmitting the user action information to the document security server fails, the user action information is stored in a temporary database of the user computer.

  Preferably, user action information on the document is stored in binary form in the event database.

  According to still another aspect of the present invention, in the document security system, the present invention is connected to a user computer having a document security agent for generating a user-specific key and a document database in which the user computer and the document file are stored. Registering a user-specific key transmitted from the user computer, and in response to a download request for the document file from the user computer, encrypting the requested document file using the registered user-specific key; A document security server to be downloaded to the user computer, wherein the encrypted document file includes expiration date information for use of the document file, and the user computer receives the document file when browsing the document file. Time synchronization module included in the security server And then receiving the current time information of the document security server and comparing the expiration date information with the received current time information of the document security server to determine whether the document file can be used. Provide a document security system.

  Preferably, the user computer further determines whether or not the document file can be used by comparing the current time information of the environment file stored in the user computer and the expiration date information when the document file is viewed. To do.

  Preferably, the document security agent periodically connects to the document security server to update the current time information of the environment file.

  In the present invention, it is preferable that the document security server and the user computer communicate with each other using an HTTP protocol method.

  The extension of the document file encrypted in the document security server and downloaded to the user computer is preferably the same as the extension of the original document file.

  Further, the document security server includes a metabase that maintains environment setting information referred to in performing the function of the document security server in a memory, and a management tool connected to the metabase writes to the metabase (Write) operation Thus, it is preferable that the environment setting information is corrected.

  In the user computer, the user can view a plurality of encrypted documents in one program.

As described above, according to the present invention, there is an effect of providing a document security system in which security and stability are further improved as compared with a conventional document security system, and convenience for a user is improved.

  Specifically, the enterprise can completely avoid the risk of document leakage by insiders, and from the standpoint of the administrator who operates the system, through minimizing the management of the network and the safe management of the original document file It can be expected to protect the company's intellectual property and to stop the system operation.

  Also, from the standpoint of the end user, the existing document program can be used as it is without any different texture, and there is an effect that inconvenience due to the introduction of the system is not felt. In other words, there is no hindrance in the existing business, that is, it is not necessary to recognize even the use of the document protection system, and the document security system is protected.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing the overall configuration of a document security system according to the present invention.

  The document security system according to the present invention includes a document security server 100 and a client computer 200. The document security server 100 is connected to a knowledge management system or electronic document management system (not shown) for storing documents of companies and the like, and the client computer 200 is a personal PC of each user who downloads the document file. The document security server 100 and the client computer 200 communicate using the HTTP method.

  In the case of a conventional document security system, a TCP / IP system is used as a communication system between a server and a client. In this connection, most companies use firewalls for network security, and in such networks, when a document security system server and a client communicate with each other using the TCP / IP method, a specific port is opened. There were problems of administrative inconvenience and security vulnerability due to port opening. In the present invention, the document security server 100 and the client computer 200 communicate with each other by the HTTP method, which is a general web protocol, so that the burden on the administrator is reduced without being restricted by a firewall, and a specific port is opened. It also has the effect of preventing security vulnerabilities that could be a problem in the event of a problem.

  The document security server 100 includes service modules such as a time synchronization module 110, an event module 120, a key module 130, and a packager module 140, and a metabase 150 that maintains environment setting information in a memory. The document security server 100 according to the present invention also includes an event DB 170 connected to the event module 120 to store an action on a user's document; and a user DB 180 storing a user's unique information and hardware key information. Detailed descriptions of detailed functions and features of these components will be described later with reference to FIGS.

  The client computer 200 includes a document security agent 210, a document security web control unit 230 installed in the web browser 220, and a document security module 250 installed in an application program.

  In the following, each detailed component and new feature of the document security system according to the present invention will be described in detail by item.

1. Since all document files downloaded from the client document security server 100 to the client computer 200 are encrypted, the client computer 200 decrypts the document downloaded from the document security server 100 and shows it to the user. It controls actions such as reading, editing, saving, copying, and outputting documents according to the authorized authority.
In the following, the process performed on the client side will be described with reference to FIG. FIG. 2 is a flowchart showing a process performed on the client side of the document security system according to the present invention.

  Referring to FIG. 2, first, in order to open a document downloaded from the document security server 100, the user attempts to open a document file by double-clicking the mouse on the explorer or executing the corresponding application (S300). .

  Next, referring to the environment file, it is determined whether the document file that the user intends to open is in a file format supported by the document security system (S310). The environment file is downloaded and stored in the client computer 200 from the document security server 100 during the user key registration process, and will be described in detail later.

  If the document file to be opened by the user is not in a file format supported by the document security system or if it is a non-encrypted file, an error message is output (S350), and the file format supported by the document security system is used. If there is, the process proceeds to step S320.

  Next, the client computer 200 uses the document security agent 210 and communicates with the time synchronization module 110 of the document security server 100 to check whether the usage period of the document has expired (S320). The process of checking whether or not the usage period of the document associated with the time synchronization module 110 has expired will be described later with reference to FIG.

  If the document use period has expired, an error message is output (S350), and if it is determined that the use period remains, the process proceeds to step S330.

  Using the hardware key of the client computer extracted from the client computer 200 as a decryption key, the document encrypted in the document security server 100 is decrypted (S330). This is because, in the process of registering the user-specific key in the document security server 100, the key is generated as a hardware key of the client computer and transmitted to the document security server 100, and the document security server 100 sends the key to the client computer 200. This is because when the document is downloaded, the corresponding document file is encrypted through the user unique key. The use of the user hardware key as the user unique key will be described later with reference to FIGS.

  The user can view the decrypted document (S340), and uses the document according to the authority set in the document security server 100. For example, if the user does not have edit authority, the user cannot edit the downloaded document (keyboard input, mouse use, copy, paste, cut, etc.). If the user does not have print output authority, the user cannot edit the document. Cannot print out. If the user does not have the right to save, the user cannot save the downloaded document or save it with a name. If the user has the right to save, the user can encrypt the contents including the modified contents. And saved. In the case where there is no authority in relation to the client-side interface related to each of these authority settings, for example, it can be created in an inactive state where the corresponding menu of the application cannot be used.

On the other hand, in the present invention, the encrypted document file has an extension of the original document (for example,
. doc) is used as it is. As described above, in the conventional document security system, the encrypted document file transmitted to the user computer is in a format in which the extension is changed regardless of the format of the original document (for example, the original document security system). If the original document file is in the form of .doc, the encrypted document file will be changed to the form of .acap-the extension name thus changed was determined) There was a problem that it was not known what type of document was actually encrypted. According to the present invention, by using the extension of the original document file as it is as the extension of the encrypted document file, the user can easily determine what type of file the original document of the encrypted document is. There is an effect to make it understand. With respect to the distinction between encrypted documents in the present invention, for example, an encrypted document can be distinguished from an unencrypted document by visually adding a lock image to a file icon.

  Further, in browsing documents on the client side of the security system of the present invention, the present invention supports an MDI (Multiple-Document Interface) environment.

  In the conventional document security system, when a user views an encrypted document, only one document can be viewed in one program, and when a user tries to view a new document, Had the inconvenience of having to run the program. That is, the program has to be executed as many as the number of documents to be viewed. However, in the present invention, when a user browses a plurality of documents, in the case of documents of the same type, an encrypted document and an unencrypted document can be used simultaneously in one program, and a plurality of non-encrypted documents can be used. Encrypted documents can be used simultaneously. In the case of an encrypted document, as described above, the menu and toolbar of the application are controlled according to the authority set for the document.

  On the other hand, the conventional document security system controls only the “Print Screen” key of the keyboard in connection with the limitation of the screen capture, so that a utility that specializes in screen capture cannot control it.

  In the present invention, in order to prevent screen capture, the screen capture utility controls the screen capture at the Windows (R) O / S level, so that even if the screen capture utility is used, the document is stored as an image. Storage can be limited.

2. Key Module Next, a process performed in association with the key module 130 of the document security system will be described with reference to FIG. FIG. 3 is a flowchart illustrating a process performed in association with the key module of the document security system according to the present invention, and particularly relates to a process in which the user registers his / her user key in the document security server 100.

  Referring to FIG. 3, first, the user connects to the document security system (S400). Next, a hardware key specific to the user PC is extracted from the client computer (S410). The user hardware key extracted here is used as an encryption key for the document file in the document security server 100, and is used as a decryption key for decrypting the document after the user has downloaded the document.

In order to encrypt a document so that the document can be viewed only by a specific user PC, a key dependent on the hardware of the corresponding user is required. For this reason, the encryption / decryption key of the document is used. The user unique key is extracted from the hardware information of the user PC. Such a user hardware key is a user-specific string value, which in the preferred embodiment of the present invention has a length of 16 bytes.

  In extracting the user hardware key, the UUID module installed in the client computer 200 extracts the manufacturer, model name, production serial number, etc. of the H / W (HDD, USB, etc.), which is a specific 16 bytes. The hardware key is generated by changing the value to.

  In the conventional document security system, there is a problem that such a user hardware key is registered in a specific location of the client computer, for example, a registry, and can be copied or converted by the user. In the present invention, the module for extracting the user hardware key is incorporated in the document security agent 210 so that the user key is transmitted to the document security server 100 and managed only once when the key is registered. Is done. Accordingly, the user cannot copy his / her key to others and use it illegally, and has the effect of making any modification to the user hardware key impossible.

  Next, the generated hardware key is combined with the user information and formed into a packet, and the packet including the hardware key is transmitted from the client computer 200 to the key of the document security server 100 through the HTTP communication protocol. It is transmitted to the module 130 (S420).

  In transmission of such a hardware key from the client computer 200 to the document security server 100, the packet is transmitted after being encrypted by, for example, a Blowfish encryption algorithm. By encrypting and transmitting the packet including the hardware key in this way, it is possible to protect the transmission of the key from a sniffing attempt that may occur during the transmission process of the key and prevent the risk of hacking.

  The key module 130 of the document security server 100 decrypts the received packet to check whether there is an abnormality, and checks the license through the USB license key 190 attached to the document security server 100. The license key 190 is a key for storing license information related to the user such as the number of times that the user can register, and will be described in detail later.

  Next, the user hardware key is registered and stored in the user DB; 180 linked to the key module 130 (S440), and the document security server 100 transmits the processing result to the client computer, thereby the user hardware key. The key extraction and registration process ends.

3. Packager Module The packager module 140 of the document security server 100 performs a function of encrypting the requested document file and transmitting it to the client.

  FIG. 4 is a flowchart illustrating a process performed in association with the packager module (ie, the document encryption and distribution module) of the document security system according to the present invention.

  Referring to FIG. 4, first, a user connects to the document security system and requests download of a specific document file (S500), and the packager module 140 searches the user DB and requests the download of the document file. Is obtained (S510).

  Microsoft IIS (Internet Information Server) in the document security server 100 of the present invention supports an ASP (Active Server Pages) component, and in the document security system of the present invention, a user authority setting and a document file download request are created by the ASP component. Is done.

  Next, the rule manager (not shown) combines the document information and the authority information for a specific user to set parameters for downloading the document file (S520). For the set parameter, primary encryption is performed by the AES encryption algorithm, and secondary encryption is performed by the BASE64 encryption algorithm. The encrypted parameters are received by the ASP component of the packager module 140, and the received encrypted parameters are first decrypted with BASE64 and secondarily decrypted with AES. Next, the packager module 140 refers to the license file 194 to check whether the document file has an extension supported by the system (S530). Detailed description related to the license file 194 will be described later.

  The parameter decrypted by the packager module 140 includes the user ID of the requested user. The packager module 140 refers to the user ID and is stored in the key registration process from the user DB; The download request user hardware key is extracted (S540).

  Next, the document file requested to be downloaded is encrypted through the user hardware key (S550), and the encrypted document is transmitted from the document security server 100 to the client computer 200 (S560).

  Hereinafter, a specific encryption process and file format will be described in detail.

  The format of the encrypted document file according to the present invention will be described with reference to FIG. FIG. 5 is a diagram showing a document file format according to the present invention.

  Referring to FIG. 5, the encrypted document file according to the present invention includes a signature 600, a variable length header 610, and a file body 620.

  The signature (Signature: 600) has a size of about 8 to 10 bytes having basic information indicating that the corresponding document file is an encrypted file (ie, DRM file: 270) used in the document security system. Information, and this signature 600 part is not encrypted.

  In the present invention, the client side determines whether or not the file is encrypted through the signature 600 portion that is not encrypted, and then decrypts the header portion. In the conventional security system, there is no signature part as in the present invention, and only the encrypted header with a fixed length of 128 bytes is included. Therefore, when the file is opened, all the header parts are decrypted. This has the problems of increasing time delay and system load. As in the present invention, according to the file structure including the signature in the front part of the header, the file open time can be shortened and the load on the system can be reduced.

  The variable length header 610 is mainly composed of an entry point (Entry Point) and a number of structures (Structure).

  The entry point (Entry Point) includes a header size field indicating the length of the header, a structure number field indicating the number of unit structures, and the like in the structure in which the header has a variable length as in the present invention. The field is extremely important.

  Each structure is a block expressing one meaningful DRM information. The plurality of structures included in the header 610 according to the present invention include a content information structure including company code and document encryption time, and a corresponding file. Including an authentication information structure including information related to the authentication of the file, a key information structure including information related to the encryption key of the corresponding file, and a user's authority for the corresponding file, that is, editing, saving, outputting, expiry date information, etc. There is a rule information structure.

  In the present invention, since the header has a variable length as described above, the length of the file differs depending on each document, thereby maintaining a safer file structure and ensuring safety that is not easily cracked.

  In the conventional document security system, as described above, having a fixed-length header of 128 bytes has a problem that it is difficult to accept this when a new function is added or a corporate demand arises. there were. However, according to the present invention, the configuration having the variable length header 610 including a dummy field having an arbitrary size allows new functions and new customer requests to be added at any time. Even if the version is upgraded, the previous file structure can be used continuously.

  On the other hand, the variable length header 610 in the present invention is encrypted using the key included in the license file 194, and a detailed description related to the license file 194 will be described later.

  The file body 620 of the document file of the present invention is encrypted using the user unique key included in the header 610. According to the preferred embodiment of the present invention, the document file is divided into 4 kilobyte (Kbytes) unit blocks by using a Rijndal encryption algorithm in the encryption of the document file body. In the conventional document security system, there is a problem that the system load is increased by adopting a method of encrypting the entire data at once. In the present invention, by encrypting a document file in units of 4 Kbytes as described above, there is an effect that time is shortened even when a large capacity file is encrypted and decrypted, and the load on the system is reduced. There is an advantage that encryption is possible.

  If the file to be encrypted is smaller than 128 bytes, it is encrypted with an encryption algorithm different from the Lindal encryption algorithm because the minimum unit of the Lindal encryption algorithm is 128 bytes. It is. In this way, by selecting and using the encryption algorithm according to the size of the file, there is an effect of improving the encryption performance and reducing the size of the encrypted file.

  On the other hand, in the present invention, a document file stored in the document DB of the document management system, that is, a document file that has not yet been encrypted with the user hardware key is also encrypted and stored. By doing so, the document file can be secured even when the company's document management system is directly hacked from the outside.

In the present invention, the document file distributed to the user is encrypted with the user-specific key dependent on the user's hardware according to the above embodiment, and when the document file is leaked, the copyright holder and the legitimate It is also possible to embed a watermark and a fingerprint that can confirm information for a new user.

  Watermarking technology is a technology that has begun to be developed to protect the copyright of content, and conceals information for the copyright holder in the content. Technology that can be used for this purpose. The watermark technique is classified into a visible watermark technique that can be visually confirmed and an invisible watermark technique that cannot be visually confirmed.

  The fingerprinting technique embeds not only copyright holder information but also user information such as a distributor, redistributor, and final consumer in order to confirm a valid user of the content. If the user arbitrarily communicates content to a third party without any permission, this is considered illegal distribution and will identify the illegal distributor based on the detected fingerprint information. In other words, by applying fingerprinting technology, it is possible to trace afterwards who has illegally distributed the content, and to ask the responsibility.

  In other words, the fingerprinting technique can be used to track the outflower when the internal document is leaked in the future by outputting information for the user together with a part of the output document. The easiest way is to visually alert the user to the spill by printing the output time and information for the output person visually at the bottom of the output document. However, since there is a high possibility that the visible information is removed by the user in this way, in the present invention, the user cannot be seen visually, but it is utilized for tracking by concealing the information inside the document. Provide the function to do.

4). Event module A user performs a series of actions on a document downloaded from the packager module 140. Such actions may include opening, editing, saving, outputting, and the like of a document. As described above, actions may be restricted by the authority set and encrypted in the document security server 100.

  The event module 120 of the document security server 100 performs a function of reporting such a user action from the client computer 200 and storing it.

  Hereinafter, a process performed in association with the event module 120 will be described with reference to FIG. FIG. 6 is a flowchart illustrating a process performed in association with an event module of the document security system according to the present invention.

  Referring to FIG. 6, first, the user performs a predetermined action (opening, editing, saving, outputting, etc.) a document distributed in encrypted form, that is, a DRM document 270 (S700). The predetermined action on the user's document is transmitted to the document security agent 210 (S710), and the document security agent 210 reports the predetermined action on the user's document to the event module 120 of the document security server 100. Then, a network connection is attempted (S720).

  The network between the document security server 100 and the client computer 200 is not always activated. If the network is activated and the network connection is successful, the event module 120 saves the user action information transmitted from the document security agent 210 in the event DB 170 (S750).

If the network is not activated and the network connection fails, the user action information is generated and stored in the client computer 200 by generating a temporary DB (Temp DB) (S730). The document security agent 210 later attempts to connect to the network again and retransmits the user action information stored in the temporary DB to the event module 120 (S740), and the retransmitted user action information is stored in the event DB 170. (S750).

  On the other hand, in the present invention, such user action information is stored in the event DB; 170 in binary form. If the user's action information is stored in a simple text file, anyone can easily open it with a simple text editor program, which can be a security vulnerability. In the present invention, the user action information is stored in the event DB; 170 in binary form in this way, so that the information can be viewed only through a specific dedicated utility, and the security is enhanced.

5). Time synchronization module Depending on the nature of the document, it may be useful to set the rights associated with the document's available maturity date. For this reason, the authority information included in the header of the encrypted document may include maturity date information related to the time when the document can be viewed. However, there is a problem that a user can illegally use a document whose expiration date has passed by intentionally changing the time of his / her PC in the past, that is, before the expiration date. In order to prevent this, time synchronization must be performed between the client computer 200 and the document security server 100, and the time of the document security server 100 has priority over the time of the client computer 200. There must be. The time synchronization module 110 of the document security server 100 is a component that performs functions related to the use of maturity date information as authority information for such a document and time synchronization.

  Hereinafter, a process performed in association with the time synchronization module 110 will be described with reference to FIG. FIG. 7 is a flowchart illustrating a process performed in association with the time synchronization module of the document security system according to the present invention.

  Referring to FIG. 7, first, the user attempts to open an encrypted document file (S800), and at the same time, the current time of the client computer 200 is obtained (S810). The expiration date information included in the variable length header portion of the encrypted document file is extracted, and the extracted expiration date information is compared with the current time of the client computer 200 (S820).

  As a result of the comparison, if the expiration date is earlier than the current time of the client computer 200, the document is closed and the user cannot use the document (S880). Otherwise, the client computer 200 connects to the time synchronization module 110 of the document security server 100 and receives the current time of the document security server 100 (S830).

  The received current time of the document security server 100 is compared with the expiration date information. If the comparison result shows that the expiration date is past the current time of the document security server 100, the document is closed and the user can use the document. (S880). Otherwise, the current time stored in the environment file 260 in the client computer is obtained (S850).

In this connection, the document security agent 210 periodically updates the current time information of the environment file 260 to the current time information of the time synchronization module 110 in connection with the network of the document security server 100. That is, if the time information of the document security server 100 is the latest value than the time information defined in the environment file, the current time information of the environment file is updated, whereby the document security server 100 and the client computer 200 are updated. Can be synchronized.

  Further, as a result of comparison with reference to FIG. 7, if the expiration date is earlier than the current time of the environment file, the document is closed and the user cannot use the document (S880). Otherwise, the user can browse and use the document (S870).

6). License Management The document security system of the present invention provides license management for the document security server program. The document security license (DSL) of the present invention is issued when a purchaser of a document security system such as a company decides to purchase and purchases a product.

  The document security license according to the present invention includes a user access license (UAL: User Access License) which is a license for the number of users to be used and a user software license (USL: User Software License) which is a license for supporting user software (file extension) Consists of. Providing such document security license management provides the flexibility to meet the needs of customers such as companies, and the appropriate license options depending on the functions of the document security system selected by the company Is selected.

  A license issuance is defined by a license file 194 and a license H / W key 190. That is, when the license issuance procedure is completed, a license file is generated on the administrator computer of the document security server, and license information is inserted into the USB key connected to the USB port.

First, the license file 194 defines a file format (extension) to which DRM is applied in the document management system of the purchasing company, that is, to which document security encryption is applied.
In this connection, as described above with reference to FIG. 4, when the packager module 140 of the document security server 100 performs the document encryption process according to the user's document download request, the packager module 140 Prior to encryption, the license file 194 is referenced to check whether the document file requested for download is a document file having an extension supported by the system, and is defined in the license file 194. If the file does not have an extension supported by the system, the document file is not encrypted.

  On the other hand, when each client computer 200 in the present invention registers a user hardware key, an environment file is generated from the document security server 100 and transmitted to the client computer 200. Thus, the environment file downloaded to the client computer 200 includes file extension license information defined in the license file. Accordingly, as described above with reference to FIG. 2, when the user tries to open the document file on the client computer 200, the environment file 260 including such license information is referred to, and the system supports the extension. If it is not a child file, an error message is output and the document cannot be opened.

  Next, the license H / W key is provided to a purchaser of a company or the like together with a license file, and the document security system to which DRM is applied in the document management system (EDMS, KMS,...) Of the purchaser. Manage the number of final users.

In this connection, as described above with reference to FIG. 3, in the process in which the user hardware key is stored in the user DB 180 through the key module 130 of the document security server 100, the key is stored in the user DB 180. In the previous stage, the number of times that the user can be registered is checked through the USB license H / W key 190. If the final number of users is exceeded, key registration cannot be performed.

7). Environment File An environment file (Config File) includes information such as a company code and is created when a program is installed in the document security server 100 and stored in a specific location on the server 100. The file name of the environment file should be the company code of the relevant company. It has a cfg extension. On the other hand, when the user finishes registering the user unique key in the document security server 100, the environment file is distributed and stored in the client computer 200.

  In the conventional document security system, only one piece of information about the document security server that can communicate with the client computer is maintained, so if the user needs to visit many business sites, documents cannot be downloaded at other business sites. It was.

  In the present invention, the environment file including the company code information is downloaded and used by the user when registering the key, so that even when the user goes to another business location, the environment file of the corresponding document security server is saved. Furthermore, it can be downloaded and used so as to be compatible with reference to the previous environment file.

  On the other hand, the environment file includes information related to the time synchronization module, information related to the event module, support file extension information included in the license file, etc. in addition to the company code information. It can be used for time update, transmission of user action information to the event module, and document browsing restriction on the client computer.

8). The document security server 100 of the metabase document security system is composed of various functional modules 110, 120, 130, and 140, and there are specially defined values that should be referred to for performing the functions of these modules. . Such a value is called an environment variable, and the environment variable may be changed during the operation of the document security server 100.

  In a conventional document security system, such an environment variable is stored in the Windows (R) registry (Windows (R) Registry) when the server program is initially started. If the environment setting value is not applied unless it is terminated and restarted, the server process has to be stopped.

In the present invention, in order to solve such a problem, when one or many processes are operated in one information storage system, a metabase (Metabase: 150) in which environment setting information to be referred to is made into a database. Is configured in the document security server 100.
The configuration and operation of the metabase 150 are performed as follows. First, a shared memory is created, and a database is generated in the shared memory with a specific structure. The environment variable value written to the metabase 150 generated by using the management tool 160 is modified, and the server process performed in each functional module refers to the environment variable value located in the metabase 150.

  In the present invention, by introducing and referring to the metabase 150 that maintains the environment setting information in the memory in this way, even if the environment setting is changed, the environment setting information can be obtained in real time without stopping the server process. Has the effect of being updated.

  The present invention has been particularly shown and described with reference to the above examples, which are merely used for illustration and are intended to be used by those skilled in the art to which the present invention pertains. Various modifications are possible within the technical idea and scope of the present invention as defined in the scope of the above.

It is a block diagram which shows the whole structure of the document security system by this invention. 4 is a flowchart illustrating a process performed on the client side of the document security system according to the present invention. 4 is a flowchart illustrating a process performed in association with a key module of a document security system according to the present invention. 6 is a flowchart illustrating a process performed in association with the packager module of the document security system according to the present invention. It is a figure which shows the document file format by this invention. 6 is a flowchart illustrating a process performed in association with an event module of the document security system according to the present invention. 4 is a flowchart illustrating a process performed in association with a time synchronization module of the document security system according to the present invention.

Explanation of symbols

  100 document security server, 110 time synchronization module, 120 event module, 130 key module, 140 packager module, 150 metabase, 160 management tool, 170 event DB, 180 user DB, 190 license key, 192 document file, 194 license file, 200 client computer, 210 document security agent, 220 web browser, 230 document security web control unit, 240 application, 250 document security module, 260 environment file, 270 DRM file, 600 signature, 610 variable length header, 620 file body.

Claims (28)

In the document security system,
A user computer having a document security agent for generating a user-specific key;
The registered user is connected to the user computer and the document database in which the document file is stored, the user unique key transmitted from the user computer is registered, and the registered user is responded to the document file download request from the user computer. A document security server that encrypts the requested document file using a unique key and downloads it to the user computer;
The document security system, wherein the user specific key is generated using information extracted from hardware information of the user computer.   2. The document security system according to claim 1, wherein the module for extracting the user unique key is built in the document security agent.   The document security system according to claim 1, wherein the user unique key is transmitted from the user computer to the document security server in an encrypted form.   4. The document security system according to claim 3, wherein the encryption of the user specific key is based on a blowfish encryption algorithm.   2. The document according to claim 1, wherein, prior to registration of the user-specific key in the document security server, it is checked whether or not the number of times a user can be registered is exceeded through a license key attached to the document security server. Security system.   6. The document security system according to claim 5, wherein the license key is inserted into a USB key connected to a USB port of the document security server.   After the user unique key is registered, an environment file (Config File) including company code information of a company related to the document security server is transmitted from the document security server to the user computer and stored therein. The document security system according to claim 1. In the document security system,
A user computer having a document security agent for generating a user-specific key;
The registered user is connected to the user computer and the document database in which the document file is stored, the user unique key transmitted from the user computer is registered, and the registered user is responded to the document file download request from the user computer. A document security server that encrypts the requested document file using a unique key and downloads it to the user computer;
The document security system, wherein the encrypted document file includes a variable length header including authority setting information for controlling authority of the user to the document.   9. The document security system according to claim 8, wherein the authority for the document includes one or more of a viewing authority, an editing authority, a saving authority, an output authority, and an expiration date-related authority.   9. The document security system according to claim 8, wherein the variable length header includes a dummy field having an arbitrary size. 9. The document security system according to claim 8, wherein the encrypted document file includes a signature indicating that the document file is an encrypted file.   12. The document security system according to claim 11, wherein the signature is not encrypted.   9. The document security system according to claim 8, wherein the document file is encrypted by being divided into blocks of 4 kilobytes (Kbytes).   9. The document security system according to claim 8, wherein the document file stored in the document database is encrypted and stored.   9. The document security system according to claim 8, wherein the document file is encrypted using the user-specific key, and at the same time, a watermark including copyright holder information is embedded in the document file.   9. The document security system according to claim 8, wherein the document file is encrypted using the user unique key, and at the same time, a fingerprint including information for a valid user is embedded in the document file.   The document security server may check whether the requested document file is a document file having an extension supported by the system through a license file prior to encryption of the document file. The document security system according to claim 8. In the document security system,
A user computer having a document security agent for generating a user-specific key;
The registered user is connected to the user computer and the document database in which the document file is stored, the user unique key transmitted from the user computer is registered, and the registered user is responded to the document file download request from the user computer. A document security server that encrypts the requested document file using a unique key and downloads it to the user computer;
The document security agent of the user computer transmits user action information for the downloaded document to an event module included in the document security server, and the user action information for the document transmitted to the event module is: A document security system stored in an event database connected to the document security server.   The document security system according to claim 18, wherein the user's action on the document includes one or more of a document browsing action, a saving action, an editing action, and an output action.   19. The user action information is stored in a temporary database of the user computer when a network connection to transmit the user action information to the document security server fails. Document security system.   19. The document security system according to claim 18, wherein user action information on the document is stored in the event database in binary form. In the document security system,
A user computer having a document security agent for generating a user-specific key;
The user computer and a document database in which document files are stored are linked,
Registering a user-specific key transmitted from the user computer, and in response to a download request for the document file from the user computer, encrypting the requested document file using the registered user-specific key; A document security server downloaded to the user computer,
The encrypted document file includes expiration date information for use of the document file, and the user computer connects to a time synchronization module included in the document security server when browsing the document file. After receiving the current time information of the document security server, the expiration date information is compared with the received current time information of the document security server to determine whether or not the document file can be used. Security system.   The user computer further determines whether or not the document file can be used by comparing the current time information of the environment file stored in the user computer and the expiration date information when browsing the document file. 23. A document security system according to claim 22, characterized in that:   The document security system according to claim 23, wherein the document security agent periodically connects to the document security server to update current time information of the environment file.   The document security system according to any one of claims 1 to 24, wherein the document security server and the user computer communicate with each other by an HTTP protocol method.   25. The extension of a document file encrypted in the document security server and downloaded to the user computer is the same as the extension of the original document file. Document security system. The document security server includes a metabase that maintains environment setting information referred to in performing the function of the document security server on a memory;
The document security system according to any one of claims 1 to 24, wherein the environment setting information is modified by an operation of writing to the metabase by a management tool connected to the metabase.   25. The document according to claim 1, wherein the user computer can simultaneously browse a plurality of encrypted documents and non-encrypted documents in one program. Security system.

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