KR100414188B1 - Method and apparatus for protecting digital documents - Google Patents

Abstract

For digital copyright protection and information security of digital documents transmitted on-line and off-line, digital documents are transformed and processed on a page-by-page basis for graphics, encryption, compression, and arrangement. The digital document thus processed can maintain the same shape as a graphic file. Therefore, although the shape can be confirmed using a normal image viewer, it cannot grasp the actual content. Restoration of the form can restore the file in the form of an image, restore, decompress, decode, and restore the graphic form back to the original digital document using the information of the file.

Description

METHOD AND APPARATUS FOR PROTECTING DIGITAL DOCUMENTS}

The present invention relates to a method for securing a digital document and an apparatus using the same. More specifically, for the protection of copyright and information security of digital documents transmitted online or offline, the security functions are enhanced to prevent the leakage of information by processing digital documents according to their specific characteristics rather than in the form of a single file. The present invention relates to a method for securing a digital document and an apparatus using the same.

Recently, information such as documents and data are digitized by computers, and as the Internet, e-mails, and storage media are developed, there is an opportunity to obtain desired data more quickly and easily. In addition, the development of interactive services that transmit such digital content in real time, and networking technology that connects them are being made in a quantum leap.

However, due to the nature of digital information, not only can you easily make the same copy or modification as the original, but also it can be easily distributed anywhere. May lead to weakening. In addition, the recent establishment of local area networks (LANs) and knowledge management systems (KMS) in the enterprise has been actively promoted. As a result, the possibility of information disclosure by companies and institutions is increasing.

Therefore, the demand for the protection technology of digital information is increasing rapidly, and the technology in the field of technology and service to prevent illegal distribution and use is being developed.

Conventional technologies include system log-in management and system management techniques to block illegal access of the system, digital rights management (DRM) technology that protects, secures, and manages digital documents, and user restriction methods for mail. It provides its own related technologies and solutions.

First of all, firewall technology for system security, network security, and facility security is mainly to prevent illegal intrusion from the outside, and its purpose is to prevent intrusion from the outside rather than managing users of companies or institutions. Therefore, it has a disadvantage in that it cannot play a role against illegal intrusions or activities in a company or institution.

In addition, DRM technology, which recently appeared as a technology for protecting and managing information copyright, prevents illegal distribution and duplication of multimedia information, manages users so that only legitimate users can use the information, and manages multimedia information through billing services such as payment. The technology of managing copyright.

However, while DRM technology is currently accepted as a realistic solution to protect and manage the copyright of digital information in the market, the structure and system of the already developed DRM technology is very complicated and bloated, and the user actually applies the service to apply it. It is not easy to do. In particular, the management of authentication key used by general users to actually purchase and replay the information is often operated entirely by the DRM server provider, and the actual information is also sent to the server registrant to register and encrypt it. Since it is received and operated again, when it is used by a general company or an institution other than a company that makes a profit through the provision of digital information, the dual task of sending and receiving the information back to the server registrant in terms of system construction and actual information management is required. It is inconvenient and the transmission path becomes complicated, which increases the possibility of information leaking in the middle.

In the case of such DRM, there is a concern that source contents can be easily distributed when encryption surrounding information is released. In addition, in the information protection using the existing DRM, the route of the information provider and the information user constitutes a one-way route, and thus, the communication of the distribution system through mutual exchange of opinions in the information distribution system is difficult.

In case of applying such DRM technology for document security such as enterprise or government, it is difficult to apply other than commercial information because it is inconvenient to send all the target documents for security to server registrant, encrypt them, and then receive them and distribute them again. It also has its drawbacks.

In the case of document security through the management of e-mail, the list can be controlled by limiting the size of the e-mail attachment, controlling the traffic of TCP / IP, or monitoring by searching for specific words about the content of the e-mail. It is a technology to create and report, to call attention through an alarm, or to monitor the user. However, document security through the management of e-mails has a problem of violating individual freedom in that it monitors personal information of companies and organizations.

In recent years, in addition to e-mail, file transfer is possible through the World wide web (WWW) or FTP (File Transfer Protocol), and also includes floppy diskettes, zip discs and jazz discs. ), There is a problem that can not block the path of information leakage through the development of large-capacity storage media such as compact disc (compact disc).

Moreover, in recent years, data security, data and programs can be transmitted wirelessly through a mobile phone or a PDA. Thus, document security through the control of e-mail has revealed a limitation.

Accordingly, an object of the present invention is to secure a digital document for providing a secure type of document that can prevent the leakage of information or forgery / falsification of information that may occur when exchanging information in order to solve the problems described above. It is to provide a method and an apparatus using the same.

Another object of the present invention is a method for security of a digital document that prevents the leakage of information that may occur in a document output on-line or off-line, and even if the main information is illegally leaked so that its contents cannot be encrypted and verified in a graphic form. It is to provide a device using the same.

Another object of the present invention is to reduce the load on the network through the encryption and compression process while maintaining the content of the digital document as it is, and to secure the security of the digital document that minimizes the errors that may occur when data transmission or offline output is damaged. To provide a method and an apparatus using the same.

1 is a block diagram showing a schematic configuration of an apparatus for securing a digital document according to the present invention.

FIG. 2 is a block diagram functionally dividing the configuration of the encryption unit in FIG. 1.

3 is a block diagram showing the configuration of the compression unit in FIG.

4 is a block diagram showing the configuration of the error correction unit in FIG.

FIG. 5 is a block diagram functionally dividing the configuration of the arrangement in FIG. 1. FIG.

6A to 6H show examples of pattern arrangements made in the arrangement section, and show a case where the digital document consists of five patterns.

7 is a block diagram showing a schematic configuration of another embodiment of a security apparatus for a digital document according to the present invention.

8 is a block diagram illustrating a schematic configuration of an apparatus for decrypting a secure document generated in accordance with the present invention.

※ Explanation of codes for main parts of drawing

100 .. Digital document (target document) 105 ... Graphic processing unit

110 ... Encryption section 120 ... Compression section

130 ... error correction 140 ... array

150 ... secure documents 160 ... alignment

170 ... Error Correction 180 ... Extension

190 ... Decryptor 195 ... Graphic Decryptor

200 ... decrypted document

An apparatus for the security of a digital document according to the present invention for achieving the above object is

Means for encrypting the digital document by a predetermined encryption scheme;

Means for compressing the encrypted digital document by a predetermined compression scheme;

Means for correcting errors in the compressed digital document by a predetermined error correction scheme; And

And means for forming the error-corrected digital document into a pattern of a predetermined size and arranging the error-corrected digital document in a predetermined order.

In addition, the method for security of the digital document according to the present invention

Sequentially arranging patterns constituting the digital document in the form of an image generated by the security device of the digital document in the original order and restoring the digital document from the pattern;

Correcting an error occurring during transmission or copying of the restored digital document;

Decompressing the digital document by applying an inverse algorithm during compression to decompress the error corrected digital document; And

And decrypting the encrypted decompressed digital document.

In the present invention having the above characteristics, basically, the target document is generated and stored in a personal computer or temporarily stored by an application tool. That is, from the moment when a digital object document is produced and has value as information of contents, it is intended to present a method and an apparatus using the same that can enhance security of a digital document according to the present invention.

Hereinafter, a method for securing a digital document and an apparatus using the same according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram schematically showing the configuration of an apparatus for security of a digital document according to the present invention.

As shown in FIG. 1, the apparatus for security of a digital document according to the present invention includes an encryption unit 110 for encrypting a target document 100, a compression for reducing the size of an encrypted document to increase transmission efficiency, and the like. The unit 120 includes an error correction unit 130 for correcting an error that may occur during data transmission or reproduction and increasing a detection rate, and an arrangement unit 140 for arranging respective documents in a predetermined form.

Looking at the operation performed in each component of the security device of the digital document having the above configuration in more detail as follows.

First, the target document 100 is a word document and a database file, a spreadsheet, graphic data, a program generated by a word processing program such as Microsoft's MS-WORD or Hangul and Hangul's Hangul Hangul, which is being created or targeted by a user. Refers to a series of files created in the form of a digital document through a computer such as the source code of the document, and hereinafter referred to as a digital document.

The encryption unit 110 performs an encryption operation to prevent illegal distribution of the digital document 100. Encryption can be divided into a case of performing encryption using an encryption key for a digital document and a case of maintaining dual security by separately managing a key for decrypting the encrypted information together with the encryption. In the former case, a single encryption key is used to encrypt a digital document, while the latter uses two encryption keys to perform double encryption. The latter case will be described with reference to FIG. 2.

FIG. 2 is a block diagram schematically showing an example of an encryption unit in the security apparatus of a digital document according to the present invention in FIG. As shown in FIG. 2, the encryption unit 110 generates a session key encryption unit 112 for generating a session key for encrypting the digital document for authentication of the use of the information. A session key encryption unit 114 that performs encryption for the encryption key, a super key encryption generation unit 116 that generates a super key for encrypting a key that decrypts the encrypted information, and a number for encrypting the decryption key by the generated super key. Perky encryption unit 118 is included.

The basic function of the encryption unit 110 is that only a legitimate user with an encryption key can decrypt and use an encrypted digital document, and protects information by disabling the key even if it is illegally distributed. First, the session key encryption generation unit 112 generates a session key and provides the session key to the session key encryption unit 114. The sensing key encryption unit 114 encrypts the digital document 100 using the session key. After encryption is performed on the digital document 100 itself, a super key capable of decrypting the session key used for encryption is generated using the super key encryption generator 116. When the super key is generated, the super key encrypting unit 118 encrypts a digital document encrypted using the super key and a session key capable of decrypting the document. The super key encryption unit 118 binds and encrypts the session key and the digital document encrypted by the session key.

As such, the encryption of the digital document and the decryption key for decrypting the encrypted digital document can be encrypted and managed again using the super key to further increase the security and prevent the key from being leaked by hacking or the like. . The encryption keys (session key and superkey) used have a byte length of a predetermined size or more, and in the present invention, an encryption key having a length of 16 bytes or more is used and the length thereof is not particularly limited. Various encryption algorithms can be used. As an example of the encryption algorithm, a twofish encryption algorithm, a blowfish encryption algorithm, or the like may be used.

The digital document encrypted by the encryption unit 110 is subjected to a compression process for reducing the capacity of the digital document encrypted by the compression unit 120. The compression unit 120 performs a compression process using a compression algorithm that is basically set, and additionally includes a compression algorithm generation unit 125 to provide various types of compression algorithms. The compression unit 120 serves to reduce the size of the digital document and protect the encryption key by removing a duplicate part existing in the data of the encrypted digital document through a predetermined process.

Therefore, in the case of not the application tool according to the present invention, various compression methods exist, and if it cannot be confirmed, it is difficult to check the contents of the target document. Compression algorithms can be applied to various compression algorithms like encryption. For example, Shannon-Fano code compression algorithm, Hoffman code compression algorithm, Jones code compression algorithm, FGK algorithm. (Faller-Gallager-Knuth algorithm), V-algorithm (Vitter algorithm) and the like can be used as an example.

That is, when the encryption method is determined, the compression algorithm generating unit 125 generates a compression algorithm according to the corresponding method, and accordingly, the compression unit 120 compresses the encrypted document. After the compression of the digital document is made, the capacity of the digital document is checked. Checking the capacity of the digital document can be done to compare the size of the capacity before and after compression and to check whether the compression is normal. If there is a problem with the size, select the new compression method and perform the compression process. You can also do it again.

After the digital document is compressed by the compression unit 120 to reduce the capacity, the digital document is input to the error correction unit 130. The error correction unit 130 corrects an error that may occur during data transmission or playback and increases a detection rate. As in the compression unit 120, the error correction unit 130 may perform error correction by a specific method, and additionally includes an error correction code generation unit 135 in various forms according to a user's selection. Error correction can be performed.

In addition, the error correction unit 130 is a printer that can be generated offline or when you want to convert the secure document 150 output offline on-line through the recognition process, such as scanning according to the use example of the present invention or It is used to minimize the inability to recognize documents due to document damage. The error correction code used in the above process may include a burst error correction algorithm, a reed-solomon error correction algorithm, a cyclic redundancy check (CRC) method, and the like.

When the error correction method is determined as described in the compression unit 120, the error correction code generation unit 135 generates an error correction code according to the corresponding method, and accordingly the error correction unit 130 compresses the document. Insert the error correction code for. After error correction is made to the digital document, check the error correction code. If the digital document's error correction code is checked in the same way as the inserted error correction code, the error correction code is wrong.Therefore, the error correction code has a problem. Create and perform error correction.

The arranging unit 140 may include a pattern forming unit 142 for generating an error-corrected digital document in a predetermined pattern according to its value, and a pattern arranging unit for dividing the generated pattern into predetermined sizes and arranging them in a predetermined order. 144, and includes a pattern combining unit 146 for combining the patterns arranged in a predetermined order as one file to format the encrypted and compressed target document into a certain form.

The encrypted and compressed target document input to the arranging unit 140 is converted into a pattern having a predetermined size by the pattern generating unit 142. As an example of such a pattern, the present invention is based on a pattern having a square combination of two-dimensional form of 48 * 48 as one cell, but the size or shape thereof is 12 * 12, 24 * 24 or rhombus as needed. , Rectangular, etc. can be adjusted. The pattern forming unit 142 arranges the data generated by the error correction unit 130 in a series of orders. For example, when the data is represented in binary, the black dot is 1 and the white space is 0. It can be represented by the expression, and it can be arranged in a series of orders according to the shape of the cell in two-dimensional form.

As described above, when the patterns are formed by sizes, the pattern arrangement unit 144 does not change the order as shown in FIG. 6A and the arrangement of the patterns in one-dimensional form as shown in FIGS. 6B to 6H. Various adjustments can be made in two-dimensional form. The arrangement of patterns is more secure because the information may be exposed to a third party when the digital document is transformed by generating a pattern according to the characteristics of the data for a simply compressed and error-corrected digital document. For this purpose, the digital document is patterned and these patterns are arranged in various forms to make recognition of the digital document almost impossible.

When the patterns for the digital document are arranged in a predetermined form, the pattern combiner 146 combines them into one file. In other words, in the process of creating and arranging patterns, these patterns are divided, but they are combined so that they can be recognized as if they are one pattern. Combining the plurality of patterns arranged in this way has the advantage of making it more robust to attack from the outside by combining as a pattern in the form of an image.

As such, when the processing of the digital document in the arrangement unit 140 is completed, the secure document 150 is obtained. The secure document 150 can be confirmed by combining an encrypted cell form and again arranging it in the form of an image through a conventional image viewer, but the contents thereof are encrypted. Images of the secure document 150 may be copied in a computer, posted as an image on an email, FTP, or the web, or output offline through an output means. However, the secure document 150 can be freely copied online or offline, but only in the form of the image, and the contents of the image are processed by encryption, compression, and pattern arrangement as mentioned above. It is impossible to grasp.

Another embodiment of the security apparatus for a digital document according to the present invention as described above will be described with reference to FIG. The security device shown in FIG. 7 differs from the security device in FIG. 1 in that it includes a graphic processing unit 105 before the encryption process for the digital document made by the encryption unit 110.

The graphic processor 110 performs graphic processing in consideration of the characteristics of the digital document (target document) 100. For example, suppose a digital document is a word document. Word document is separated by each page, and the page contains invisible special codes and visible texts and pictures such as spacing adjustment, character size or form, page length, and page change according to the characteristics of the document. Included. The data about the special code and the content of the document can be understood as to what basic frame the digital document has by identifying the content of the header portion of the digital document. The analysis also reveals information about the data, which is the actual content of the digital document. Of course, this information is different for various digital documents. It is possible to grasp the type and contents of the digital document by checking the type of the file stored in the header of the digital document and referring to the separate information according to the type of the file. In general, the type of the file of the target document can be simply recognized by using the file identifier.

As described above, when the type of digital document is determined, graphic processing of the document is performed for each page. The graphic processing converts data corresponding to text in a document and parts corresponding to a special code into image data using a conversion table. This conversion uses a method of forming a two-dimensional bar code or an optical watermark to convert the data into a predetermined form to construct data of an image. Such graphic processing on a digital document is performed for the whole page.

After the graphic processing for the digital document, encryption, compression, error correction, and arrangement processing as in the previous embodiment are performed, and as a result, a secure document 150 can be obtained. As described above, according to the second embodiment including the graphic processor 105, the decryption of the secure document 150 may be more difficult, and thus security may be further enhanced.

When the security operation on the digital document is processed by the security apparatus of the digital document according to the present invention as described above, since the digital document cannot be decrypted by the existing method, the contents contained in the secure document 150 are not included. In order to decipher, it must be processed through the reverse process made in the present invention. This reverse process will be described with reference to the security apparatus of the digital document according to the present invention shown in FIG.

As shown in Fig. 8, the security apparatus of the digital document according to the present invention includes a sorting unit 160 for arranging the secure documents 150 patterned and arranged in a predetermined order in the original order, and transmitting them from the sorted pattern. Or error correction unit 170 for correcting errors in copying or copying, decompressing unit 150 for decompressing the digital document in which the error is corrected, and an encrypted digital document in a decipherable form. And a decryption unit 190 for decoding, and the decrypted document 200 is converted into the original digital document (target document) 100 through the process from the alignment unit 160 to the decryption unit 190. Becomes

The above process will be described in more detail by component.

First, the secure document 150 is patterned and since the pattern has changed in its arrangement in a predetermined order, the alignment unit 160 rearranges the pattern to decrypt the secure document 150. In the above process, since the user does not know the cell or the pattern of the cell provided by the arrangement unit 140 and the arrangement thereof, the user rearranges them in a form that the user can decrypt.

In order to convert the secure document 150 output through the offline output into a document that can be recognized by the user, an image of the offline image can be used online through an input device such as a scanner in front of the alignment unit 160. The process is required separately.

At this time, the header portion of the secure document 150 includes information related to the arrangement of the pattern, and this information is also configured to occupy a certain portion in the image portion of the secure document 150. Sort by The same can be applied to the case where the secure document 150 is output on a paper or the like. The secure document 150 formed of one image may be sequentially arranged in the order of the contents of the digital document by dividing the image according to the size and arrangement of the cell and rearranging the arrangement of the pattern. After the patterns are sequentially arranged in this manner, the contents of each cell constituting the pattern may be restored to the digital document after error correction by performing a reverse process of the original formation.

The error correction unit 170 undergoes a series of processes for correcting an error occurring during transmission or copying and extracting a target document for the digital document restored from the pattern. In particular, the error correction unit 170 outputs the offline output through the printer is low resolution, or the toner of the printer almost consumes a part of the image is not output, or the printed printout is physical incomplete (crumpled, writing instruments In some cases, damage caused by water, or bleeding of the print due to sweat or water, may be necessary to restore the original document closer to the original document.

After the error correction is completed, the decompression unit 180 decompresses the data for decompressing the digital document in which the error is corrected. The expansion unit 180 is a process for visualizing the result obtained through the error correction unit 170 in a compressed form. The expansion unit 180 may reproduce the contents compressed by the compression unit 120 described above by applying an inverse algorithm to the target document of the same type.

The digital document extended by the decompression unit 180 is decoded for decryption by the decoding unit 190. The operation of the decryption unit 190 may be considered by dividing into two cases as mentioned above with respect to the encryption unit 110. Basically, a digital document can be divided into a case where it is simply encrypted and additionally a case where a double document is encrypted. When the digital document is simply encrypted, the decrypted document 200 may be obtained by decrypting the digital document using a decryption key.

When the digital document is encrypted twice, the session key is decrypted through the super key, and the encrypted document is decrypted through the session key and converted into the target document 100. At this time, the decryption unit 190 receives the super key separately and decrypts the encrypted session key to extract the session key. Through this process, a session key is generated, and through this, the decryption unit 190 decrypts the target document using the session key to obtain a decrypted document 200.

In the second embodiment shown in FIG. 7 of the security apparatus for the digital document according to the present invention, since the target document 100 is further processed by the graphic processing unit 105 for graphic processing, the decryption unit 190 Even if decrypted, the original target document 100 cannot be obtained. Therefore, the graphic decryption unit 195 includes a document in the form of a graphic image divided into pages, and is converted into a document of the original form. Since the target document 100 is already in the graphics processing rule, the inverse transformation converts the data in the image form back into portions corresponding to text and portions corresponding to special codes. The digital document processed by this conversion is converted into the target document 100 having original characteristics.

As described above, the secure document generated by the present invention is configured to form a single image by patterning the document in a specific size and arranging the patterns in various forms even after the digital document is encrypted and compressed. This can prevent exposure of digital documents against attacks such as hacking from the outside, and since the decryption process for these digital documents can only be decrypted by the security device of the digital document according to the present invention, the security of the documents is thoroughly achieved. It can be effective.

In addition, even if the digital document itself is exposed or leaked to the outside, the contents of various documents are formed through encryption and compression while preserving the contents of the documents as they are, thereby enhancing security in the contents. As a result of the compression and error correction process, the network load can be reduced, and the safe and efficient use of documents is minimized by minimizing errors that may occur during data transmission or off-line printout.

While the invention has been particularly shown and described with reference to the above embodiments, it has been used for the purpose of illustration and those of ordinary skill in the art, having the spirit and scope of the invention as defined in the appended claims. Various modifications can be made without departing.

Claims (18)

In the device for the security of digital documents, Means for encrypting the digital document by a predetermined encryption scheme; Means for compressing the encrypted digital document by a predetermined compression scheme; Means for correcting errors in the compressed digital document by a predetermined error correction scheme; And And means for forming the error-corrected digital document into a pattern of a predetermined size and arranging the error-corrected digital document in a predetermined order. In the device for the security of digital documents, Means for converting the digital document into a graphic document according to a predetermined rule; Means for encrypting the graphically processed digital document by a predetermined encryption scheme; Means for compressing the encrypted digital document by a predetermined compression scheme; Means for correcting errors in the compressed digital document by a predetermined error correction scheme; And And means for converting the error-corrected digital document into a pattern of a predetermined size and arranging them in a predetermined order. The apparatus of claim 2, wherein the converting means divides the digital document into pages and converts the contents of the digital document into a graphic form according to a predetermined conversion table. The method of claim 1, wherein the arrangement means Pattern forming means for forming the error-corrected digital document into a pattern of a predetermined size; Pattern arrangement means for arranging the formed patterns in a predetermined order; And And a pattern joining means for joining patterns arranged in a predetermined order. The apparatus of claim 4, wherein the pattern combining means combines the patterns to form a single image. The apparatus of claim 5, wherein the form of the digital document generated by the pattern combining means can be checked using an image viewer, but the contents thereof are encrypted. The method of claim 4, wherein the encryption unit Session key encryption generating means for generating a session key for encrypting the digital document for authentication to the use of the information; Session key encryption means for performing encryption on the digital document using the generated session key; Superkey cryptographic generation means for generating a superkey for encrypting a key for decrypting the encrypted information; And A super key encryption means for encrypting the decryption key by the generated super key, And the super key encrypting means binds and encrypts the session key and the digital document encrypted by the session key. In the security device of a digital document, The pattern constituting the digital document in the form of an image generated by the security device of the digital document according to any one of claims 3, 5, 6 and 7, is sequentially arranged in the original order and the Means for recovering the digital document from a pattern; Means for correcting an error occurring during transmission or copying of the restored digital document; Means for decompressing the digital document by applying an inverse algorithm upon compression to decompress the error corrected digital document; And And means for decrypting the encrypted decompressed digital document. The digital document as claimed in claim 8, wherein the decrypting means decrypts the session key encrypted using the super key, extracts the session key, and decrypts the digital document as the decryption key for the digital document. Document security. In the method for the security of digital documents, Encrypting the digital document by a predetermined encryption scheme; Compressing the encrypted digital document by a predetermined compression scheme; Correcting an error of the compressed digital document by a predetermined error correction method; And And converting the error-corrected digital document into a pattern of a predetermined size so as to convert the image into an image form and arranging the error-corrected digital document in a predetermined order. In the method for the security of digital documents, Converting the digital document into a graphic document according to a predetermined rule; Encrypting the graphic digital document by a predetermined encryption method; Compressing the encrypted digital document by a predetermined compression scheme; Correcting an error of the compressed digital document by a predetermined error correction method; And And converting the error-corrected digital document into a pattern of a predetermined size so as to convert the image into an image form and arranging the error-corrected digital document in a predetermined order. The method of claim 11, wherein the converting step separates the digital document for each page and converts the contents of the digital document into a graphic form according to a predetermined conversion table. The method of claim 10, wherein the arranging step A pattern forming step of forming the error-corrected digital document in a pattern of a predetermined size; A pattern arrangement step of arranging the formed patterns in a predetermined order; And And a pattern combining step for combining patterns arranged in a predetermined order. 15. The method of claim 13, wherein the pattern combining step combines the patterns to form a single image. 15. The method of claim 14, wherein the digital document generated in the pattern combining step can be checked using an image viewer, but its contents are encrypted. The method of claim 13, wherein the encrypting step A session key cryptography step of generating a session key for encrypting the digital document for authentication to use of the information; A session key encryption step of performing encryption on the digital document using the generated session key; A super key cryptographic step of generating a super key for encrypting a key for decrypting the encrypted information; And A superkey encryption step of encrypting the decryption key by the generated superkey, And said super key encrypting step binds and encrypts said session key and a digital document encrypted by said session key. In the security method of the digital document, 17. The pattern constituting the digital document in the form of an image generated by the security apparatus of the digital document according to any one of claims 12, 14, 15 and 16 is sequentially arranged in the original order and the Recovering the digital document from a pattern; Correcting an error occurring during transmission or copying of the restored digital document; Decompressing the digital document by applying an inverse algorithm during compression to decompress the error corrected digital document; And And decrypting the encrypted extended digital document. 18. The digital document as claimed in claim 17, wherein the decrypting step decrypts the session key encrypted by using a super key to extract the session key and decrypts the digital document as the decryption key for the digital document. Document security method.