KR102311996B1 - Device and method for anti-forensic unlocking for media files - Google Patents

Abstract

The present invention relates to a device and method for releasing an anti-forensic for a media file, wherein the device comprises: an encrypted file receiving part that receives an encrypted file generated as a result of encrypting a non-encrypted file; a secret key verification code obtaining part that obtains a secret key verification code associated with the encrypted file; a user secret key restoration part that restores a unique user secret key used in the encryption process by using the secret key verification code; and a non-encrypted file generating part that generates the non-encrypted file by decrypting the encrypted file based on the encrypted file and the user secret key. Therefore, the present invention can decrypt the encrypted data by analyzing an application that provides data encryption.

Description

DEVICE AND METHOD FOR ANTI-FORENSIC UNLOCKING FOR MEDIA FILES

The present invention relates to an anti-forensic decryption technology for a media file, and more particularly, to an anti-forensic decryption apparatus and method for a media file capable of decrypting encrypted data by analyzing an application that provides data encryption.

As the convenience of mobile devices increases, users and mobile devices are forming a close relationship. In addition, since personal information such as call history and messages are stored in mobile devices, users' awareness of personal information protection is increasing. Accordingly, a personal information protection application for preventing invasion of privacy has been released. Privacy protection applications provide various techniques such as data hiding and encryption so that only authorized users can access data.

On the other hand, although privacy protection applications are designed to protect personal information, there are many cases where they are used as a means of destroying evidence of criminal activity because it makes it difficult to access data. However, for digital forensics who need to collect data to prove criminal activity, data protection techniques can act as an anti-forensic activity. Therefore, as a countermeasure against this, research to acquire original data through privacy protection application analysis is essential.

Korean Patent Laid-Open Patent No. 10-2007-0001055 (2007.01.03)

An embodiment of the present invention is to provide an anti-forensic decryption apparatus and method for a media file capable of decrypting encrypted data by analyzing an application providing data encryption.

An embodiment of the present invention provides an anti-forensic release device and method for media files that can effectively respond to the destruction of evidence of criminal activity by analyzing the data hiding and encryption process acting as an anti-forensic from the digital forensic investigation point of view. .

An embodiment of the present invention provides an anti-forensic decryption apparatus and method for a media file that provides decryption of an encrypted file using a signature that is formed differently according to an encryption target and can recover a user input password based on user verification data would like to provide

Among the embodiments, the anti-forensic decryption device for the media file includes an encrypted file receiving unit that receives an encrypted file generated as a result of encrypting a non-encrypted file, and obtains a secret key verification code for obtaining a secret key verification code associated with the encrypted file unit, a user secret key restoration unit that restores a unique user secret key used in the encryption process using the secret key verification code, and decrypts the encrypted file based on the encrypted file and the user secret key to decrypt the non-encrypted file It includes a non-encrypted file generator for generating a file.

The encrypted file and the non-encrypted file may be independently stored in an uppermost folder of an external file storage area.

The secret key verification code obtaining unit generates the secret key verification code as a result of repeatedly applying the hash function to the user secret key, and in the repeated application process, the first hash function is a hash function using the user secret key as an input. A value is generated as an output, but the rest of the hash function may use a value generated through a concatenation operation between the hash function value of the previous step and the user secret key as an input.

The user secret key restoration unit uses the candidate user secret key as the user secret key when the result value repeatedly applied to the hash function from among a plurality of candidate user secret keys sequentially generated by the generation rule matches the secret key verification code can decide

The non-encrypted file generator decomposes the encrypted file to extract a signature, a first variable, a second variable, and a ciphertext, respectively, and the signature is determined differently according to the target of the encryption, and the second The size of the variable may be formed to be larger than the size of the first variable.

The signature may have a size of at least 6 bytes and include a counter that increases according to the number of times of encryption when the target of the encryption is a file name.

The non-encryption file generator may generate a secret code by applying a hash function to the user secret key, and generate the encryption key using the secret code and the second variable as input parameters of a first encryption algorithm.

The unencrypted file generation unit can generate the unencrypted file by decrypting the encryption process of a second encryption algorithm that generates the cipher text as an output using the unencrypted file, the encryption key, and the first variable as input parameters. have.

In embodiments, the anti-forensic decryption method for a media file includes receiving an encrypted file generated as a result of encrypting an unencrypted file, obtaining a secret key verification code associated with the encrypted file, and the secret key verification code restoring the unique user secret key used in the encryption process using

The disclosed technology may have the following effects. However, this does not mean that a specific embodiment should include all of the following effects or only the following effects, so the scope of the disclosed technology should not be construed as being limited thereby.

The anti-forensic release apparatus and method for a media file according to an embodiment of the present invention can effectively respond to the destruction of evidence of criminal activity by analyzing the data hiding and encryption process acting as an anti-forensic from the digital forensic investigation point of view.

The anti-forensic decryption apparatus and method for a media file according to an embodiment of the present invention provides decryption of an encrypted file using a signature that is formed differently depending on an encryption target, and can recover a user input password based on user verification data. have.

1 is a view for explaining an anti-forensic release system according to the present invention.
FIG. 2 is a diagram for explaining a physical configuration of the anti-forensic release device of FIG. 1 .
FIG. 3 is a view for explaining a functional configuration of the anti-forensic release device of FIG. 1 .
FIG. 4 is a flowchart illustrating an anti-forensic release process for a media file performed by the anti-forensic release device of FIG. 1 .
5 is a diagram for explaining the file structure of an encrypted file according to the present invention.
6 to 9 are diagrams for explaining an encryption process for a media file according to the present invention.

Since the description of the present invention is merely an embodiment for structural or functional description, the scope of the present invention should not be construed as being limited by the embodiment described in the text. That is, since the embodiment may have various changes and may have various forms, it should be understood that the scope of the present invention includes equivalents capable of realizing the technical idea. In addition, since the object or effect presented in the present invention does not mean that a specific embodiment should include all of them or only such effects, it should not be understood that the scope of the present invention is limited thereby.

On the other hand, the meaning of the terms described in the present application should be understood as follows.

Terms such as “first” and “second” are for distinguishing one component from another, and the scope of rights should not be limited by these terms. For example, a first component may be termed a second component, and similarly, a second component may also be termed a first component.

When a component is referred to as being “connected” to another component, it should be understood that the component may be directly connected to the other component, but other components may exist in between. On the other hand, when it is mentioned that a certain element is "directly connected" to another element, it should be understood that the other element does not exist in the middle. Meanwhile, other expressions describing the relationship between elements, that is, “between” and “between” or “neighboring to” and “directly adjacent to”, etc., should be interpreted similarly.

The singular expression is to be understood to include the plural expression unless the context clearly dictates otherwise, and terms such as "comprises" or "have" refer to the embodied feature, number, step, action, component, part or these It is intended to indicate that a combination exists, and it should be understood that it does not preclude the possibility of the existence or addition of one or more other features or numbers, steps, operations, components, parts, or combinations thereof.

Identifiers (eg, a, b, c, etc.) in each step are used for convenience of description, and the identification code does not describe the order of each step, and each step clearly indicates a specific order in context. Unless otherwise specified, it may occur in a different order from the specified order. That is, each step may occur in the same order as specified, may be performed substantially simultaneously, or may be performed in the reverse order.

The present invention can be embodied as computer-readable codes on a computer-readable recording medium, and the computer-readable recording medium includes all types of recording devices in which data readable by a computer system is stored. . Examples of the computer-readable recording medium include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage device, and the like. In addition, the computer-readable recording medium may be distributed in a network-connected computer system, and the computer-readable code may be stored and executed in a distributed manner.

All terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, unless otherwise defined. Terms defined in general used in the dictionary should be interpreted as being consistent with the meaning in the context of the related art, and cannot be interpreted as having an ideal or excessively formal meaning unless explicitly defined in the present application.

1 is a view for explaining an anti-forensic release system according to the present invention.

Referring to FIG. 1 , the anti-forensic release system 100 may include a user terminal 110 , an anti-forensic release device 130 , and a database 150 .

The user terminal 110 may correspond to a computing device capable of receiving a password from a user, encrypting a non-encrypted file, and generating an encrypted file as a result. To this end, the user terminal 110 may install and execute a dedicated application that provides data encryption. For example, the dedicated application may include an application that provides an encryption function to encrypt a media file such as a photo or video file.

In addition, the user terminal 110 may be implemented as a smartphone, a notebook computer, or a computer, and is not necessarily limited thereto, and may be implemented in various devices such as a tablet PC. The user terminal 110 may be connected to the anti-forensic release device 130 through a network, and a plurality of user terminals 110 may be simultaneously connected to the anti-forensic release device 130 .

The anti-forensic release device 130 may be implemented as a server corresponding to a computer or program capable of decrypting an encrypted file to restore a non-encrypted file and recovering a password used in an encryption process. Also, the anti-forensic release device 130 may be connected to the user terminal 110 through a wired network or a wireless network such as Bluetooth or WiFi, and may communicate with the user terminal 110 through a wired or wireless network. The anti-forensic unlocking device 130 may store various pieces of information necessary to perform a decryption operation on an encrypted file in conjunction with the database 150 .

Meanwhile, the anti-forensic release device 130 may be implemented by including the database 150 therein, unlike FIG. 1 . The anti-forensic release device 130 may be implemented including a processor, a memory, a user input/output unit, and a network input/output unit as a basic system configuration, which will be described in more detail with reference to FIG. 2 .

The database 150 may store various pieces of information necessary for the anti-forensic unlocking device 130 to analyze the application and decrypt the encrypted data. For example, the database 150 may store information about an encrypted file obtained from the user terminal 110 and may store information about a non-encrypted file generated as a result of decrypting the encrypted file, but is not necessarily limited thereto. Instead, information collected or processed in various forms can be stored in the process of generating a non-encrypted file based on the encrypted file by applying the anti-forensic deactivation method.

FIG. 2 is a diagram for explaining a physical configuration of the anti-forensic release device of FIG. 1 .

Referring to FIG. 2 , the anti-forensic release device 130 may be implemented including a processor 210 , a memory 230 , a user input/output unit 250 , and a network input/output unit 270 .

The processor 210 may execute a procedure for processing each step in the process of the anti-forensic release device 130 operating, and manage the memory 230 that is read or written throughout the process, and the memory ( 230) may schedule a synchronization time between the volatile memory and the non-volatile memory. The processor 210 may control the overall operation of the user detection device 130 , and is electrically connected to the memory 230 , the user input/output unit 250 , and the network input/output unit 270 to control data flow between them. can The processor 210 may be implemented as a central processing unit (CPU) of the anti-forensic release device 130 .

The memory 230 is implemented as a non-volatile memory, such as a solid state drive (SSD) or a hard disk drive (HDD), and may include an auxiliary storage device used to store overall data required for the anti-forensic release device 130, and , and may include a main memory implemented as a volatile memory such as random access memory (RAM).

The user input/output unit 250 may include an environment for receiving a user input and an environment for outputting specific information to the user. For example, the user input/output unit 250 may include an input device including an adapter such as a touch pad, a touch screen, an on-screen keyboard, or a pointing device, and an output device including an adapter such as a monitor or a touch screen. In an embodiment, the user input/output unit 250 may correspond to a computing device accessed through a remote connection, and in such a case, the anti-forensic release device 130 may be implemented as a server.

The network input/output unit 270 includes an environment for connecting with an external device or system through a network, for example, a local area network (LAN), a metropolitan area network (MAN), a wide area network (WAN), and a VAN (Wide Area Network) (VAN). It may include an adapter for communication such as Value Added Network).

FIG. 3 is a view for explaining a functional configuration of the anti-forensic release device of FIG. 1 .

Referring to FIG. 3 , the anti-forensic unlocking device 130 includes an encrypted file receiving unit 310 , a secret key verification code obtaining unit 330 , a user private key restoring unit 350 , a non-encrypting file generating unit 370 and a control unit. (390).

The encrypted file receiving unit 310 may receive the encrypted file generated as a result of encrypting the non-encrypted file. The encrypted file may correspond to a file encrypted by an application executed by the user terminal 110 , and the non-encrypted file may correspond to a media file such as a picture or a video as an original encrypted file. Meanwhile, in the present invention, encryption and decryption of media files are mainly described, but the present invention is not necessarily limited thereto, and the present invention can be applied to various types of files. The encrypted file may be generated on the user terminal 110 , and the encrypted file receiving unit 310 may receive the encrypted file by accessing a specific location where the encrypted file is stored on the user terminal 110 .

In an embodiment, the encrypted file and the non-encrypted file may be stored independently of each other in the top-level folder of the external file storage area. The encrypted file may be generated by a dedicated application operating on the user terminal 110 , and may be stored in a specific location on the user terminal 110 according to the operation of the dedicated application.

For example, the SafeCamera application can store encrypted and non-encrypted files by creating SafeCamera and SafeCameraDecrypted folders respectively in the top-level folder of the external file storage. Here, when the SafeCamera application is used for the first time, access to the application can be controlled by registering a user input password, and the target of the encryption/decryption function corresponds to photos taken through the application and previously stored photos and video files. can do. In addition, the SafeCamera application immediately encrypts and stores the captured photos, and when the previously stored media files are encrypted, the encryption can be performed by checking whether the original data has been deleted.

The secret key verification code obtaining unit 330 may obtain a secret key verification code associated with the encrypted file. A dedicated application that provides encryption may provide a means of protecting the encrypted file so that decryption of the encrypted file is impossible when the user input password is unknown. Applications do not store passwords in plaintext, but may store data for password verification to ensure that only authorized users can access them.

That is, the secret key verification code obtaining unit 330 may obtain the secret key verification code as password verification data associated with the encrypted file. The location where the secret key verification code is stored and the file to be stored may be different depending on the application. For example, in the case of the SafeCamera application, data for password verification may be stored in the hidden processing file '.hash' in the 'SafeCamera' folder and 'default_prefs.xml' in the package subfolder 'shared_prefs'.

In one embodiment, the secret key verification code obtaining unit 330 may generate the secret key verification code as a result of repeatedly applying the hash function to the user's private key. At this time, in the process of repeatedly applying the hash function, the first hash function uses the user secret key as an input and generates a hash function value as an output, but the rest of the hash functions perform a concatenation operation between the hash function value of the previous step and the user secret key. The generated value can be used as input. In this case, it can be expressed as follows.

1) Hash Value A = SHA512(Password)

2) Verify Data = SHA512(Hash Value A || Password)

That is, the secret key verification code obtaining unit 330 hashes the user secret key (that is, corresponding to the user input password) through the SHA512 hash function, and connects the user secret key to the result value once again and hashes it with the SHA512 hash function. As a result, a secret key verification code can be generated.

The user secret key restoration unit 350 may restore the unique user secret key used in the encryption process by using the secret key verification code. That is, the user secret key may correspond to the user input password used in the encryption process. More specifically, the user secret key restoration unit 350 restores the user secret key based on the secret key verification code by reversely using the operation process of obtaining the secret key verification code by repeatedly applying the hash function to the user secret key. can do. As a result, the user secret key restoration unit 350 can easily verify the user secret key by using the SHA512 hash function twice.

In one embodiment, the user secret key restoration unit 350 is the candidate user secret key when the result value repeatedly applied to the hash function from among the plurality of candidate user secret keys sequentially generated by the generation rule matches the secret key verification code can be determined as the user secret key. For example, the SafeCamera application uses a minimum of 6 characters for the user input password, and it is recommended to use a combination of 0~9, a~z, and A~Z plus 6 special characters as 12-character input characters. The user secret key restoration unit 350 may sequentially generate a plurality of candidate user secret keys by applying the corresponding generation rule, and compare the result of repeatedly applying the SHA512 hash function to each candidate user secret key with the secret key verification code. Through the verification process, the user's secret key can be finally determined.

Meanwhile, the user secret key restoration unit 350 may perform a recovery experiment for restoring the user secret key, and the experimental environment is Processor: intel(R) Core(TM) i7-4790 CPU, Threads: single, Memory (ram). ): 32.0 GB, System: can be built like windows 10 x64. Specific experimental results for this are as follows. That is, it took 0.16 s for Password digits 1, 0.28 s for Password digits 2, 2.60 s for Password digits 3, 2.41 m for Password digits 4, and 2.89 h for Password digits 5. , it was estimated that it would take 8.18 days for Password digits 6 and 556.8 days for Password digits 7.

For reference, according to the benchmark of Hashcat, a hash function-based password recovery tool, it is possible to use the SHA512 hash function more than 2.2 billion times per second based on one RTX 2080 ti GPU. It means that password verification is possible about 1.1 billion times per second for simple calculations. Therefore, based on one RTX 2080 ti GPU, a six-digit password can be recovered in about 90 seconds or less, and it may take about 68 times or less for each digit thereafter.

The non-encrypted file generation unit 370 may generate a non-encrypted file by decrypting the encrypted file based on the encrypted file and the user's secret key. An application that provides encryption for a media file may generate an encrypted file as a result of performing an encryption operation by receiving a user secret key based on an unencrypted file. That is, the non-encrypted file generating unit 370 may restore the encrypted file by reversely applying the encryption operation to the non-encrypted file, and in this process, the user secret key restored by the user secret key restoration unit 350 is can be used

In an embodiment, the non-encrypted file generator 370 decomposes the encrypted file to extract a signature, a first variable, a second variable, and a ciphertext, respectively. Here, the signature, the first variable, and the second variable may correspond to parameters used in the encryption process, and may serve to provide unpredictability to protect the encryption process from external attacks. In this case, the signature may be determined differently depending on the target of encryption, and the size of the second variable may be larger than the size of the first variable. The structure of the encrypted file will be described in more detail with reference to FIG. 5 .

In one embodiment, the signature is formed in a size of at least 6 bytes and may include a counter that is increased according to the number of times of encryption when the target of encryption is a file name. For example, the signature may correspond to 'SCAES.' if the encryption target is data of a media file, and may correspond to 'zzSC-cnt_' if the encryption target is the file name of a media file. In order to guarantee the effect to a certain level, the signature is generated with a size of at least 6 bytes and can be used in the encryption process. Meanwhile, cnt of the file name signature is a counter to prevent overwriting due to duplication when encrypting different data with the same signature, and may be incremented by 1 when encrypting a media file through a dedicated application.

In one embodiment, the non-encryption file generation unit 370 generates a secret code by applying a hash function to the user secret key, and generates an encryption key using the secret code and the second variable as input parameters of the first encryption algorithm. can That is, the first encryption algorithm may correspond to an algorithm for generating an encryption key. For example, a SafeCamera application can generate a cryptographic key using a SHA512 hash function and PBE as its cryptographic algorithm. In addition, the SafeCamera application can use the hash value as a passphrase of the PBE after hashing the user's secret key with a hash function. The encryption key generation process may be as follows.

1) Passphrase = SHA512(Password)

2) Key = PBEwithSHA256and256bitAES-CBC-BC(Passphrase, Salt, 2048, 256)

Here, Passphrase may correspond to a secret code, Password may correspond to a user secret key, Key may correspond to an encryption key, and Salt may correspond to a second variable. The PBE may correspond to Password Based Encryption, and may correspond to an algorithm capable of encryption by generating variables necessary for encryption such as Salt and Iv based on the secret code. SafeCamera applications can only use PBEwithSHA256and256bitAES-CBC-BC for encryption key generation. In addition, the salt used for PBE may correspond to 32-byte random data generated through SHA-1PRNG.

In one embodiment, the non-encrypted file generation unit 370 decrypts the encryption process of the second encryption algorithm that generates a cipher text as an output using the non-encrypted file, the encryption key, and the first variable as input parameters to generate the non-encrypted file. can create That is, the second encryption algorithm may correspond to an algorithm for generating a ciphertext. For example, the SafeCamera application can perform cryptographic operations using AES-256-CBC/PKCS#7, where an unencrypted file, an encryption key and a first variable can be used as input parameters, Ciphertext = AES It can be expressed as -256-CBC/PKCS#7 (Plaintext, Key, Iv). Here, Ciphertext may correspond to ciphertext, Plaintext may correspond to plaintext, and Iv may correspond to the first variable.

Meanwhile, the encryption process performed by the non-encrypted file generating unit 370 may be summarized as follows.

1) Passphrase = SHA512(Password)

2) Key = PBEwithSHA256and256bitAES-CBC-BC(Passphrase, Salt, 2048, 256)

3) Ciphertext = AES-256-CBC/PKCS#7(Plaintext, Key, Iv)

The control unit 390 controls the overall operation of the anti-forensic unlocking device 130 , the encrypted file receiving unit 310 , the secret key verification code obtaining unit 330 , the user private key restoring unit 350 , and the non-encrypting file generating unit It can manage the control flow or data flow between 370 .

4 is a flowchart illustrating an anti-forensic release process for a media file performed by the anti-forensic release device of FIG. 1 .

Referring to FIG. 4 , the anti-forensic unlocking device 130 may receive the encrypted file generated as a result of encrypting the non-encrypted file through the encrypted file receiving unit 310 (step S410 ). The anti-forensic release device 130 may acquire the secret key verification code associated with the encrypted file through the secret key verification code obtaining unit 330 (step S430).

In addition, the anti-forensic release device 130 may restore the unique user secret key used in the encryption process using the secret key verification code through the user secret key restoration unit 350 (step S450). The anti-forensic decryption apparatus 130 may generate a non-encrypted file by decrypting the encrypted file based on the encrypted file and the user's secret key through the non-encrypting file generating unit 370 (step S470).

5 is a diagram for explaining the file structure of an encrypted file according to the present invention.

Referring to FIG. 5 , the anti-forensic decryption apparatus 130 may generate a non-encrypted file by decrypting the encrypted file based on the user's secret key through the non-encrypting file generator 350 . In this case, the non-encrypted file generator 350 may decompose the encrypted file to extract a signature, a first variable, a second variable, and a ciphertext, respectively.

In FIG. 5 , the encrypted file generated as a result of being encrypted by the cryptographic application may be formed as a result of concatenating the signature, the first variable, the second variable, and the ciphertext in order. The first variable may correspond to Iv, and the second variable may correspond to Salt. Salt is used in the encryption key generation process and is 32-byte random data generated through SHA-1PRNG and can be concatenated in front of the ciphertext after encryption. Iv is used in the ciphertext generation process and can be concatenated before Salt as 16-byte random data generated through SHA-1PRNG. That is, the size of the second variable may be larger than the size of the first variable.

Meanwhile, the signature may provide an effect of preventing recovery of the cipher text despite exposure of the encrypted file by forming the encrypted file together with the cipher text. In particular, the signature may be formed in a size of at least 6 bytes, and may be formed differently depending on the target of encryption and added to the ciphertext. For example, if the target of encryption is data in a media file, the signature is 'SCAES.' and may correspond to 'zzSC-cnt_' in the case of a file name. The cnt of the file name signature is a counter to prevent overwriting due to duplication when encrypting different data with the same file name.

6 to 9 are diagrams for explaining an encryption process for a media file according to the present invention.

Referring to FIG. 6 , the anti-forensic unlocking apparatus 130 may decrypt an encrypted file by using the encryption process in reverse. In FIG. 6 , an encryption process for an encrypted file may be divided into three steps. The first step is a step (S610) of generating an encryption key used in the encryption process, and the second step is to generate a ciphertext using the non-encrypted file 600 and the encryption key corresponding to the input. Step S630, and the third step may correspond to step S650 of generating an encrypted file by adding a signature to the ciphertext.

Referring to FIG. 7 , the first step of the encryption process may correspond to the step of generating an encryption key used in the encryption process ( S610 ). In the step of generating an encryption key, a user password is inputted from a user, a hash function is applied to the user secret key to generate a secret code, and an encryption process is performed through an algorithm operation using the secret code and a second variable as input parameters. An operation of generating the encryption key used in the output as an output may be performed. The encryption key generated in the first step may be transferred to the second step (S630).

Referring to FIG. 8 , the second step of the encryption process may correspond to a step S630 of generating a ciphertext using an unencrypted file 600 corresponding to an input and an encryption key. In the step of generating the cipher text, the operation of generating the cipher text may be performed through an algorithm operation using the non-encrypted file 600, the encryption key generated in the first step, and the first variable as input parameters. The ciphertext generated in the second step may be transmitted to the third step (S650).

Referring to FIG. 9 , the third step of the encryption process may correspond to the step S650 of generating an encrypted file 900 by adding a signature to the encrypted text. In the step of generating the encrypted file 900, different signatures are determined depending on whether the input is file data or a file name, and the encrypted file 900 is a result of sequentially concatenating the determined signature with the first variable, the second variable, and the cipher text. ) can be created. Meanwhile, when all encryption is completed, the extension of the encrypted file 900 may be finally changed.

As a result, the anti-forensic unlocking device 130 may perform an operation of decrypting encrypted data by reversely applying an encryption process that may act as an anti-forensic action, and may recover a user input password in the process.

Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art can variously modify and change the present invention within the scope without departing from the spirit and scope of the present invention as set forth in the claims below. You will understand that it can be done.

100: Anti-Forensic Release System
110: user terminal 130: anti-forensic release device
150: database
210: processor 230: memory
250: user input/output unit 270: network input/output unit
310: encryption file receiving unit 330: secret key verification code acquisition unit
350: user secret key restoration unit 370: non-encrypted file generation unit
390: control unit
600: unencrypted file
900: encrypted file

Claims (9)

an encrypted file receiving unit for receiving an encrypted file generated as a result of encrypting the non-encrypted file;
a secret key verification code obtaining unit for obtaining a secret key verification code associated with the encrypted file;
a user secret key restoration unit for restoring a unique user secret key used in the encryption process by using the secret key verification code; and
Comprising a non-encrypted file generator for generating the non-encrypted file by decrypting the encrypted file based on the encrypted file and the user secret key,
The non-encrypted file generator decomposes the encrypted file to extract a signature, a first variable, a second variable, and a ciphertext, respectively,
The anti-forensic release apparatus for a media file, wherein the signature is determined differently according to the target of the encryption, and the size of the second variable is larger than the size of the first variable.
According to claim 1,
The anti-forensic release device for media files, characterized in that the encrypted file and the non-encrypted file are each independently stored in an uppermost folder of an external file storage area.
The method of claim 1, wherein the secret key verification code obtaining unit
To generate the secret key verification code as a result of repeatedly applying a hash function to the user secret key,
In the repeated application process, the first hash function uses the user secret key as an input to generate a hash function value as an output, but the remaining hash functions are values generated through concatenation operation between the hash function value of the previous step and the user secret key. An anti-forensic release device for media files, characterized in that it uses as an input.
The method of claim 3, wherein the user secret key restoration unit
When a result value repeatedly applied to the hash function from among a plurality of candidate user secret keys sequentially generated according to a generation rule matches the secret key verification code, the candidate user secret key is determined as the user secret key Anti-Forensic Disable Device for Media Files.
delete The method of claim 1, wherein the signature is
The anti-forensic release device for media files, comprising a counter that is formed in a size of at least 6 bytes and increases according to the number of times of the encryption when the target of the encryption is a file name.
The method of claim 1, wherein the non-encrypted file generation unit
Anti-forensic release for media files, characterized in that applying a hash function to the user secret key to generate a secret code, and generating an encryption key using the secret code and the second variable as input parameters of a first encryption algorithm Device.
The method of claim 7, wherein the non-encrypted file generating unit
In a media file, characterized in that the non-encrypted file is generated by decrypting the encryption process of a second encryption algorithm that generates the encrypted text as an output using the unencrypted file, the encryption key, and the first variable as input parameters. For anti-forensic release devices.
receiving an encrypted file generated as a result of encrypting the unencrypted file;
obtaining a secret key verification code associated with the encrypted file;
restoring a unique user secret key used in the encryption process using the secret key verification code; and
Decrypting the encrypted file based on the encrypted file and the user secret key to generate the unencrypted file,
The generating of the non-encrypted file includes decomposing the encrypted file to extract a signature, a first variable, a second variable, and a ciphertext, respectively,
The method of claim 1, wherein the signature is determined differently depending on the encryption target, and the size of the second variable is larger than the size of the first variable.

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