KR20070033926A - Method for generating standard file using information hiding technology, apparatus for checking metadata integrity of standard file format and method thereof - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method for generating a standard file using information hiding technology, an apparatus for checking the integrity of metadata thereof, and a method thereof.

2. The technical problem to be solved by the invention

The present invention provides functions such as integrity of metadata embedded in a file, authentication and non-repudiation of protection subjects, and access control, thereby acquiring a permanent relationship to metadata inside and outside the file and providing consistency of services. In order to enable the implementation of various terminal-based business models, an apparatus for checking the integrity of standard file format metadata using information hiding technology, and a method and a computer-readable recording program for realizing the method. Its purpose is to provide a record carrier.

3. Summary of Solution to Invention

The present invention provides an apparatus for checking integrity of standard file format metadata, comprising: metadata obtaining means for obtaining metadata from a protected file; Integrity proof value obtaining means for obtaining integrity proof value from a file or database (DB); Secret information extracting means for extracting secret information of the file data; And metadata integrity checking means for checking whether the metadata is correct through the obtained metadata, the integrity evidence value, and the extracted secret information.

4. Important uses of the invention

The present invention is used for a system for checking integrity of standard file format metadata.

Information concealment, standard file format, metadata, integrity, HMAC, digital signature

Description

Standard file generation method using information hiding technology and its standard file format metadata integrity checking apparatus and method thereof {Standard file generation method using a steganography technology, and apparatus and method to validate the integrity of a metadata in its}

1 is a diagram illustrating an example of a process of generating a standard file (protected file) by inserting secret information into an original file according to the present invention or calculating secret information from file data (contents) according to a predetermined formula;

2 is a diagram illustrating an embodiment of a standard file (protected file) in which integrity evidence is inserted into an original file according to the present invention;

3 is a diagram illustrating an embodiment of an apparatus for checking integrity of standard file format metadata according to the present invention.

* Explanation of symbols for the main parts of the drawings

31: file header 32: file data

33: integrity evidence 34: metadata acquisition unit

35: integrity integrity acquisition unit 36: secret information extraction unit

37: metadata integrity checker 38: content play system

The present invention relates to a method for generating a standard file using an information steganography technique, an apparatus for checking metadata integrity thereof, and a method thereof, and a computer-readable recording medium recording a program for implementing the methods. The standard inserts the integrity evidence of metadata in the file by applying various standard file formats, and based on this, integrity, authentication, and non-repudiation are applied to the metadata inserted in the file. The present invention relates to a method for generating a standard file using information hiding technology, an apparatus for checking metadata integrity thereof, and a method thereof, and a computer-readable recording medium having recorded thereon a program for realizing the method.

International / domestic standards organizations select what they think is necessary for vitalization of industry in each field and standardize through standard committee composed of expert groups. This standardized content is made into a standard document and then officially published. Therefore, anyone who understands the standard can easily obtain the information of the file created by applying the standard document.

Such standardization supports the interworking of systems and activates the industry, but also shows weaknesses in terms of security. As the IT industry develops, information becomes more and more complex. For this reason, there is a growing demand for the convenience of retrieval and storage, and for this purpose, there is a growing interest in standardization of metadata and DB of metadata. A system requiring security may develop and apply a separate security management system for managing such metadata.

Here, the metadata is data for the data, an descriptor for explaining the data, information for managing the data, and the like, and includes various types of information depending on the purpose of utilizing the data. This metadata can be managed systemically through the database, or inserted into the file's header. After all, a service consists of a combination of metadata in a file and metadata in a DB. The metadata stored in the DB is protected by the service provider, but the metadata in the file understands the file structure. Anyone can forge / false data. As a result, a situation arises in which the permanent relationship between the file data and its metadata cannot be assured, and therefore, a need exists to protect important metadata inserted into the file. In order to solve this problem, an information concealment technique for secretly inserting metadata information into file data has been studied. However, such a concealment technique is difficult to apply to practical applications due to the limited amount of information that can be inserted and a long time to extract.

Therefore, to overcome these difficulties, a method for ensuring the integrity of metadata inserted in an open standard file format using information hiding and cryptographic techniques is required.

The present invention has been proposed to meet the above requirements, and provides functions such as integrity of metadata embedded in a protected file, authentication and non-repudiation of a protection subject, and access control, thereby providing a function such as inside / outside the file. Apparatus and method for checking integrity of standard file format metadata using information concealment technology for acquiring permanent relationship to metadata, obtaining service consistency, and enabling various terminal-based business models Another object of the present invention is to provide a computer-readable recording medium having recorded thereon a program for realizing the above method.

In addition, the present invention is a standard for generating the 'protected file' by inserting secret information in the original file or calculating secret information from the file data (contents) according to a prescribed formula and generating integrity evidence of metadata. Another object is to provide a file generating method and a computer readable recording medium having recorded thereon a program for realizing the method.

Other objects and advantages of the present invention can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

An apparatus of the present invention for achieving the above object comprises: an apparatus for checking integrity of standard file format metadata, the apparatus comprising: metadata obtaining means for obtaining metadata from a protected file; Integrity proof value obtaining means for obtaining integrity proof value from a file or database (DB); Secret information extracting means for extracting secret information of the file data; And metadata integrity checking means for checking whether the metadata is correct through the obtained metadata, the integrity evidence value, and the extracted secret information.

On the other hand, the method of the present invention, in the standard file format metadata integrity checking method, when generating and consuming a protected file, the metadata is obtained from the protected file, the integrity evidence through the file or database (DB) After obtaining a value, extracting secret information of the file data; And checking whether the metadata is correct through the obtained metadata, the integrity evidence value, and the extracted secret information.

In addition, the present invention further comprises the step of generating the protected file by inserting the secret information into the original file or calculating the secret information from the file data (contents) according to a predetermined formula and generating the integrity evidence of the metadata. Characterized in that the made up.

In another method of the present invention, in the standard file generating method, inserting unique secret information pre-allocated into data (content) of a file or calculating secret information from file data (content) according to a predetermined formula. ; Inserting metadata into a header or an optional field of the file; And calculating the integrity proof value of the metadata based on the metadata and the unique code value (secret information), and inserting the calculated integrity proof value into the file or separately managing the server in a database (DB). Characterized in that it comprises a step.

On the other hand, the present invention, when requesting to generate and consume a protected file to the integrity check device of the standard file format metadata with a processor, the metadata is obtained from the protected file, and through the file or database (DB) Extracting confidential information of file data after obtaining an integrity proof value; And a computer-readable recording medium having recorded thereon a program for realizing a function of checking whether the metadata is correct through the obtained metadata, the integrity evidence value, and the extracted secret information.

The present invention further provides a function of generating the protected file by inserting the secret information into the original file or calculating the secret information from the file data (contents) according to a predetermined formula and generating the integrity proof value of the metadata. A computer readable recording medium having recorded thereon a program for realization is provided.

In addition, the present invention, in order to check the integrity of the metadata, to the standard file generating device having a processor, inserting the unique secret information previously assigned to the data (contents) of the file or file data (contents) according to a predetermined formula. Calculating secret information from; Inserting metadata into a header or an optional field of the file; And calculating the integrity proof value of the metadata based on the metadata and the unique code value (secret information), and inserting the calculated integrity proof value into the file or separately managing the server in a database (DB). A computer readable recording medium having recorded thereon a program for realizing the function of the present invention is provided.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, whereby those skilled in the art may easily implement the technical idea of the present invention. There will be. In addition, in describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating an embodiment of a process of generating a standard file (protected file) by inserting secret information into an original file or calculating secret information from file data (contents) according to a predetermined formula according to the present invention. 2 is a diagram illustrating an embodiment of a standard file (protected file) in which integrity evidence is inserted into an original file according to the present invention.

A file created using the standard file format can be arbitrarily analyzed by an object that understands the standard to read information and insert desired information. This may mean improved compatibility, but on the other hand it also poses a security vulnerability.

In order to solve such security weaknesses, information concealment techniques such as water marking and finger printing have been studied. This technology inserts a secret code into the file content itself (content) so that the file content and secret code have a continuous relationship. Recently, a technique that is robust to various attack methods has been continuously studied.

This information concealment technology uses features of the content, such as analyzing the frequency components of the image or audio and inserting secret information. Therefore, it is not possible to insert secret information through an information concealment technique in an encrypted content form that has lost all the features of the content. In this case, an information hiding technique is applied in which secret information is calculated from encrypted file data (contents) according to a predetermined formula.

In addition, if the confidential information of the file data is exposed to the malicious user, the present invention may be neutralized. Therefore, the secret information to be inserted or the secret information calculated from the file data should be well managed so as not to be exposed to the malicious person. Therefore, care should be taken to prevent leaks to the public by managing the algorithms and mechanisms for creating protected files or extracting confidential information from protected files and programs and related source codes for their implementation.

Here, the predetermined formula may be a simple form such as selecting a specific region of a file data defined by a program or a combination of several regions, or may be a result of performing an operation such as a cryptographic hash or a polynomial operation on the selected region. .

That is, in the case of an encrypted file, all audio or video features of the original content are lost due to encryption, so watermarking or fingerprinting cannot be applied to the encrypted content. To this end, a method for generating integrity evidence for encrypted content is provided in the file data (in this case, encrypted file data) using formulas (hashes of certain areas, polynomial operations and simple substitution, To calculate secret information through file data modification such as permutation).

In the present invention, the integrity and access control of metadata inserted into a header or an optional field of a file using this information hiding technique and cryptography digital signature or keyed hash message authentication code (HMAC) value, To guarantee authentication and integrity.

The security system inserts its own code (secret information) through information hiding technology or calculates secret information from the file data (content) according to a prescribed formula. The metadata to be included is included in a header or an optional field of the file. Then, the digital signature or HMAC is calculated by inputting the metadata and unique code values, added to the optional field of the file, or managed as separate information.

In the future, this information concealment technique can be used to extract code (secret information) and use the code and embedded metadata to verify digital signatures or to calculate and compare HMAC values to easily compare metadata values embedded in files. You can verify it.

The present invention can be used when the file content (contents) and metadata integrity of the file content and the technology to provide access control, authentication and non-repudiation of the file content and require high security of the file content.

As an example, forgery prevention and authentication of passport photos may be mentioned as a DRM system for digital images.

For example, when the passport issuing system is implemented in digital form using the present invention, the applicant enters his or her identity information on the application form and attaches a passport photo. At this time, the passport issuance application shall include proof of integrity, such as an electronic signature, to ensure that the identity information on the application form matches the passport photo of the attached person. At this time, if the passport photo does not contain its own secret information, a malicious person may steal the passport photo and abuse it as if it is his own photo. However, if the secret information is inserted into the passport photo using the information concealment technique or the calculated value is used as an input value for calculating the integrity evidence, even if a malicious person tries to steal the passport photo, Because we don't know the information, we can't generate the correct integrity evidence. In other words, the physically separated passport issuance application and passport photo file obtain a permanent relationship as if it is a single file that cannot be divided into two through the integrity evidence value of the passport issuance application. The generated integrity evidence will be the HMAC code value or the electronic signature value, which is the input of the passport issuance application (or the information contained in the passport issuance application) and the secret information of the passport photo.

Thus, although two files may be physically divided and given a permanent relationship to two files, two files may be combined into one file or divided into three or more files. Note that the number of physical files does not have much meaning.

That is, as described above, the file containing the metadata and the file data (content), i.e., the content does not necessarily have to be a single file, but consists of two or more files (e.g., in the passport example, the application form and If a picture is attached and there are multiple pictures or pictures and videos are attached to the application).

The above example is a case where the present invention is applied to unencrypted content (passport picture), and the following describes the case where the present invention is applied to encrypted content (passport picture is encrypted).

If the passport photo is encrypted, the file contains key management information (content ID and access information of the key management server (URL, port number, etc.)) for decrypting the encrypted passport photo in addition to the passport issuance application information described above. Is also stored together. When attempting to view the encrypted picture later, the user's terminal program extracts the key management information of the file, transfers the value to the server, and obtains the correct decryption key. However, if a malicious person changes some of the key management information and requests a content decryption key from the server, a system failure may occur due to a deny of service effect. Therefore, in order to cope with such malicious attacks, by applying the present invention to give a permanent relationship between the encrypted passport file and the key management information and guarantee the integrity, if the information is maliciously changed, the client program verifies the server You need to make sure you don't try the request. By applying this principle, it is possible to reliably serve a redistribution business model in which encrypted content is first distributed among users in a peer-to-peer format, and later receives a key and license for decrypting the content to legitimate users. In this business model, as in the case of encrypted passport photos, the key management information for obtaining the decryption key of the content is in the content file downloaded in the P2P form, which exposes the user to the risk of being changed by malicious users. If this information is changed, it can cause the above problems and can have a big impact on the reliability of the service.

In addition, the present invention can compensate for the weaknesses of the standard DRM because not only the DRM system for digital images, but also the audio / video and text-type contents can have the same effect on the contents following various standard file formats. There is an advantage.

The present invention provides a process for generating a protected file by inserting secret information into an original file or calculating secret information from file data (contents) according to a predetermined formula and generating integrity evidence 33 of metadata (FIG. 1); In the real terminal system, when the protected file is to be consumed, the process of verifying the integrity of the metadata is divided into FIG. 3.

As described above, in the process of creating a protected file (standard file), first, the unique secret information assigned to the data (content) of the file is inserted or the secret information is calculated from the file data (content) according to a predetermined formula. The metadata is inserted into a header or an optional field of the file, and then the integrity evidence value (HMAC (keyed hash message) is based on the metadata and the unique code value (secret information). authentication code) or digital signature value) is calculated and inserted into an optional field of a file or separately managed in a database of a server.

Through such a standard file (protected file) generation process, a 'protected file (standard file)' used in the integrity checking apparatus of FIG. 3 is generated.

As such, a file (standard file) protected by inserting a code into an original file has a form as shown in FIG. 2. In this case, the original file may be compressed using various multimedia compression techniques. The metadata (file header) 21 of the protected file is the same as the original metadata, and the information related to the digital signature when the digital signature technique is used for the integrity proof value 33 (the certificate subject's certificate DN (Distinguish Name)). Etc.). The integrity evidence can then be inserted 23 into the file or managed 24 separately as shown in FIG. 2.

Here, the information concealment technique may be a complex technique such as a watermarking technique or a fingerprinting technique, or may be a simple form such as selecting a specific region of a file data defined by a program or a combination of several regions, and encrypting the selected region. It can also be the result of an operation such as a hash or polynomial operation.

3 is a block diagram of an embodiment of an apparatus (terminal system) for checking integrity of a standard file format metadata according to the present invention, in which a protected file in which an integrity proof value 33 of metadata is inserted is used in a terminal system. It shows whether or not play through.

As shown in Fig. 3, the integrity checking apparatus (terminal system) of the standard file format metadata according to the present invention is used to check the integrity of the metadata before file reproduction (before executing the content play system 38). A metadata acquiring unit 34 for acquiring metadata in the protected file and an integrity evidence value 33 from the file or database 39 to check the integrity of the metadata before the file is played. An integrity evidence value obtaining unit 35 for extracting the information, a secret information extracting unit 36 for extracting secret information of the file data to check the integrity of the metadata before playing the file, and a meta before the file playing. Metadata integrity check to check whether the metadata is correct through the obtained metadata 31 and integrity evidence 33 and extracted secret information to check the integrity of the data. And a unit (37).

Here, the file header 31 is various service information and management information (connection URL of the service, content ID, key management information, content metadata, etc.) for the service using the file. The integrity proof value 33 should also include information related to the digital signature (eg, the Distinguish Name (DN) of the signing subject) when the digital signature technique is used.

File data 32 refers to file data in which secret information is inserted or calculated according to an algorithm determined for image, audio / video, and text information as contents of a file including secret information.

The integrity proof value 33 refers to an HMAC or digital signature value obtained through metadata and secret information of the file header 31.

The database 39 represents a DB server for managing the metadata integrity evidence 33 ', which is managed separately, and should always be online for integrity checking in the terminal system.

The operation of the apparatus for checking integrity of the standard file format metadata according to the present invention having the above configuration will be described in detail as follows.

In order to guarantee the integrity of the file metadata of the user in the terminal system, the user first inserts the metadata in the standard form in the original file (31). The secret data is inserted or calculated in the file data (32), and the inserted metadata and the secret information are input to generate a keyed hash message authentication code (HMAC) and have the proof value. The evidence value may be inserted into a file and used in the verification step (33) or may be kept in the DB 39 and separately managed (33 '). Such evidence values 33 and 33 'may be implemented through digital signature values rather than HMAC. When using the digital signature technique, the signature message will be a collection of metadata and secret information. At this time, the information on the signature subject should also be inserted in the metadata.

Depending on the nature of the technology, it is better to use public key method than HMAC for higher security. When using HMAC, there is no problem in ensuring integrity, but if a user intentionally inserts the secret information of another user, the authentication and non-repudiation are lost. However, if the digital signature method is used, this problem does not occur because it acquires the permanent relationship through the hidden code and the integrity, authentication, and nonrepudiation through the digital signature. Therefore, it can be said that security strength is high compared with HMAC. However, digital signature technique is more difficult to implement than HMAC and there are some items to be managed. Therefore, it should be appropriately selected and applied according to the security strength required by the application. The evidence generated in this way may be inserted into a file or transmitted to a server and stored in the DB 39.

Afterwards, the terminal system obtains evidence (33, 33 'HMAC or digital signature value) from the file or DB 39 to verify the integrity of the metadata 31 in the file and extracts secret information according to a predetermined algorithm. The verification (36) compares the HMAC values or verifies the digital signature values to verify that they are well-formed (37).

By applying this property, only the person presenting the correct evidence, that is, the packaging subject of the original file, can access control to modify the metadata of the packaged file. In addition, the terminal system may take a long time because it checks the integrity of the file metadata and consumes other information from the server using the verified metadata information to require another operation to consume the protected file. . Therefore, in order to appropriately balance the trade-off of time and security level, it is necessary to select and design an appropriate information concealment technique according to the type of file format (image, audio / video, or text).

As described above, the method of the present invention may be implemented as a program and stored in a recording medium (CD-ROM, RAM, ROM, floppy disk, hard disk, magneto-optical disk, etc.) in a computer-readable form. Since this process can be easily implemented by those skilled in the art will not be described in more detail.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

As described above, the present invention can perform authentication, non-repudiation, and access control of the metadata inserted into the open file format and the creator, thereby obtaining reliability of the metadata inserted into the file. Therefore, it is possible to obtain a permanent security relationship with respect to the metadata existing inside and outside the file and maintain the consistency of the service, thereby obtaining high security of the service.

Because of this effect, it is expected that the credibility of the metadata in the open standard file format can be obtained, and it is expected to be able to compensate for the weaknesses in the standard with important service metadata such as the DRM file format.

In addition, since the present invention can trust the metadata of the file, the terminal initiative using the metadata in the file in addition to the server initiative service using the metadata stored in the DB of the server A service model is possible, and there is an effect of more reliably supporting various transaction models between the terminal and the terminal.

Claims (19)

In the integrity checking device of the standard file format metadata, Metadata acquiring means for acquiring metadata in the protected file; Integrity proof value obtaining means for obtaining integrity proof value from a file or database (DB); Secret information extracting means for extracting secret information of the file data; And Metadata integrity checking means for checking whether the metadata is correct through the obtained metadata, the integrity evidence value, and the extracted secret information Integrity check device of the standard file format metadata comprising a. The method of claim 1, The protected file, Standard file format characterized in that the secret file is inserted into the original file or the secret information is calculated from the file data (contents) according to a predetermined formula to generate the integrity proof value of the metadata to create a protected file. Device for checking integrity of metadata. The method of claim 2, The predetermined formula is It can be a simple form, such as selecting a specific area of a file data defined by a program or a combination of several areas, and using the cryptographic hash, polynomial operation, simple substitution, and permutation for the selected area. A device for checking integrity of standard file format metadata, which may be a result of performing an operation such as calculating secret information through transformation. The method of claim 3, wherein The integrity proof value is, Calculated using cryptographic techniques such as keyed hash message authentication code (HMAC) or digital signature value obtained from the metadata of the file header and the secret information of the file data (content), added to any field of the file or Standard file format metadata integrity check device, characterized in that managed as a separate information through a database (DB). The method of claim 4, wherein The HMAC is, It inserts the previously assigned secret information into the original file or calculates secret information from the file data (contents) according to a predetermined formula, and uses the secret information as information for generating evidence of the integrity of the file metadata. Standard file format metadata integrity checking device. The method of claim 4, wherein The digital signature value is, Insert the pre-allocated secret information into the original file or calculate the secret information from the file data (contents) according to a prescribed formula, and use the secret information to generate the integrity and evidence of the file metadata. Integrity checking device of the standard file format metadata, characterized in that used as information for generating evidence for. The method according to any one of claims 1 to 6, The database, And a DB server for managing the separately managed metadata integrity proof value, and maintaining an online state for integrity checking in the terminal system. In the integrity check method of the standard file format metadata, When generating and consuming a protected file, acquiring metadata from the protected file, acquiring integrity evidence through a file or a database, and then extracting secret information of the file data; And Checking whether the metadata is correct through the obtained metadata, the integrity evidence value, and the extracted secret information Integrity checking method of the standard file format metadata comprising a. The method of claim 8, Inserting the secret information into the original file or calculating the secret information from the file data (contents) according to a predetermined formula and generating the integrity evidence of the metadata to generate the protected file Integrity checking method of the standard file format metadata further comprising. The method of claim 9, The integrity proof value is, Calculation is performed using cryptographic techniques such as keyed hash message authentication code (HMAC) or digital signature value obtained through metadata and secret information of the file header, and added to any field of the file or DB file integrity standard management method, characterized in that managed through. The method of claim 10, The HMAC is, A method for checking integrity of standard file format metadata, wherein secret information, which is inserted through an information hiding technique or calculated from file data according to a predetermined formula, is used as information for generating an evidence of the integrity of the file metadata. The method of claim 10, The digital signature value is, A method for checking integrity of standard file format metadata, which enables authentication, non-repudiation, and data access control of file metadata integrity and evidence generation subjects. In the standard file creation method, Inserting unique secret information previously assigned to the data (contents) of the file or calculating secret information from the file data (contents) according to a predetermined formula; Inserting metadata into a header or an optional field of the file; And The integrity proof value of the metadata is calculated based on the metadata and the unique code value (secret information), and the calculated integrity proof value is inserted into the file or separately managed in a database (DB) of the server. step Standard file creation method comprising a. The method of claim 13, The integrity proof value is, And a keyed hash message authentication code (HMAC) obtained through metadata and secret information of the file header. The method of claim 13, The integrity proof value is, Standard file generation method, characterized in that the digital signature value. The method of claim 15, In the case of using an electronic signature, a signature message is a collection of the metadata and the secret information, and the metadata is inserted with the information on the signature subject together with the metadata of the original file. Integrity check device for standard file format metadata with a processor, A function of acquiring metadata from the protected file, acquiring an integrity proof value through a file or a database, and extracting secret information of the file data when a consumption request for generating and consuming a protected file is requested; And Checking whether the metadata is correct through the acquired metadata, the integrity evidence value, and the extracted secret information A computer-readable recording medium having recorded thereon a program for realizing this. The method of claim 17, A function of generating the protected file by inserting the secret information into the original file or calculating the secret information from the file data (contents) according to a predetermined formula and generating the integrity proof value of the metadata. A computer-readable recording medium that records a program for further realization. In order to check the integrity of the metadata, to a standard file generating device having a processor, Inserting unique secret information pre-allocated into the data (contents) of the file or calculating secret information from the file data (contents) according to a predetermined formula; Inserting metadata into a header or an optional field of the file; And The integrity proof value of the metadata is calculated based on the metadata and the unique code value (secret information), and the calculated integrity proof value is inserted into the file or separately managed in a database (DB) of the server. function A computer-readable recording medium having recorded thereon a program for realizing this.

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