KR102216869B1 - Apparatus and method for decrypting end-to-end encrypted files - Google Patents

Abstract

The present invention relates to a decryption apparatus and method for a file to which end-to-end encryption is applied, wherein the decryption apparatus is a first encrypted file decryption unit for decrypting a first encrypted file storing a private key and a public key for a user account, the Based on the decryption result for the first encrypted file, a second encrypted file decryption unit for decrypting a second encrypted file that stores a symmetric key for encrypting the message of the user account and the decryption result for the second encrypted file And a third encrypted file decryption unit for decrypting a third encrypted file storing the message of the user account.

Description

Decryption device and method for files with end-to-end encryption applied {APPARATUS AND METHOD FOR DECRYPTING END-TO-END ENCRYPTED FILES}

The present invention relates to a decryption technology for a file to which end-to-end encryption is applied, and more particularly, a decryption apparatus for a file to which end-to-end encryption is applied, capable of obtaining important information used in an encryption process for messages between users, and It's about how.

The mobile instant messenger application encrypts all data to protect users' personal information and provides end-to-end encryption when sending messages. The private key used for message encryption can only be generated by legitimate users through the public key system, and the generated private keys are once again encrypted by their own password and stored in the device where the application is run, or use the public key system every time. Is induced by

From a digital forensic point of view, if the information of the encrypted data is unknown or it is impossible to obtain evidence, it is highly likely to be exploited by malicious criminals. Therefore, a decryption program for an encrypted messenger can be helpful for forensic investigation.

Korean Patent Registration No. 10-0666708 (2007.01.03)

An embodiment of the present invention is to provide an apparatus and method for decrypting a file to which end-to-end encryption is applied, capable of acquiring important information used in an encryption process for messages between users.

An embodiment of the present invention is to provide an apparatus and method for decrypting a file to which end-to-end encryption is applied, enabling collection of evidence and reconstruction of events without damaging original data, and collecting evidence even when a suspect does not provide a password.

An embodiment of the present invention is to provide an apparatus and method for decrypting a file to which end-to-end encryption is applied, capable of sequentially recovering user's sensitive data and finally recovering a user password based on this.

Among the embodiments, the apparatus for decrypting a file to which end-to-end encryption is applied includes a first encrypted file decryption unit for decrypting a first encrypted file storing a private key and a public key for a user account, and the first Based on the decryption result for the encrypted file, a second encrypted file decryption unit for decrypting a second encrypted file storing a symmetric key for encrypting the message of the user account and the decryption result for the second encrypted file. And a third encrypted file decryption unit for decrypting a third encrypted file storing a message of a user account.

The first and second encrypted files include data encrypted using a secret key each generated based on a password of the user account and at least one intermediate value, and the encrypted data is the at least one It can be stored concatenated in order with the median value.

The first encrypted file is generated by concatenating an identity value determined according to the location where the first encrypted file is stored and the password of the user account, and then repeatedly applying a hash function with the at least one intermediate value. It may contain data encrypted using a secret key.

The second encryption file contains data encrypted using a secret key generated by repeatedly applying a hash function to the password of the user account with the at least one intermediate value, and the number of times of the repeated application is the first encryption It can be different from the number of iterations on the file.

When the second encrypted file does not exist, the second encrypted file decryption unit is an intermediate calculated based on the private key of the user account obtained through decryption of the first encrypted file and the public key of the other party associated with the user account. The symmetric key can be obtained by applying a hash function to a value.

The second encrypted file decryption unit obtains a hashmap object through decryption of the second encrypted file, parsing the hashmap object to determine a starting point of a key, and a key and value A step of acquiring a symmetric key for each user account may be performed by searching for a separator that separates (value).

The third encrypted file decryption unit may determine a type of a message stored in the third encrypted file, and may obtain original data by decrypting an encrypted message according to the type of the message.

When the third encrypted file decryption unit downloads the encrypted message through a data link and then decrypts the message when the message type is media, and the message type is gif The original data may be downloaded through a data link obtained as a result of decrypting the encrypted message.

The decryption apparatus for a file to which the end-to-end encryption is applied may further include a password recovery unit for recovering a password of the user account using the first encrypted file or the second encrypted file.

The password recovery unit estimating a candidate password, generating a candidate key based on the estimated candidate password, applying the candidate key to an alternative encryption algorithm, and applying the candidate key to a specific block of the first encrypted file or the second encrypted file Decrypting and determining the candidate password as the password of the user account when the data obtained as a result of decrypting the specific block matches fixed data related to the first encrypted file or the second encrypted file. Can be done.

Among embodiments, the decryption method for a file to which end-to-end encryption is applied includes decrypting a first encrypted file storing a private key and a public key for a user account, based on the decryption result of the first encrypted file. Decrypting a second encrypted file storing a symmetric key for encrypting a message of a user account, and decrypting a third encrypted file storing a message of the user account based on the decryption result of the second encrypted file Includes.

The disclosed technology can have the following effects. However, since it does not mean that a specific embodiment should include all of the following effects or only the following effects, it should not be understood that the scope of the rights of the disclosed technology is limited thereby.

The apparatus and method for decrypting a file to which end-to-end encryption according to an embodiment of the present invention is capable of collecting evidence and reconfiguring events without damaging the original data, and recovering the password even if the suspect does not provide the password to collect evidence. It can be possible.

The apparatus and method for decrypting a file to which end-to-end encryption is applied according to an embodiment of the present invention may sequentially recover user's sensitive data and finally recover a user password based on this.

1 is a diagram illustrating a configuration of a decryption system for a file to which end-to-end encryption is applied according to the present invention.
FIG. 2 is a block diagram illustrating a physical configuration of the decoding apparatus in FIG. 1.
3 is a block diagram illustrating a functional configuration of the decoding apparatus in FIG. 1.
4 is a flowchart illustrating a decryption process for a file to which end-to-end encryption is applied, performed by the decryption apparatus of FIG. 1.
5 is an exemplary diagram illustrating an embodiment of a password recovery algorithm and fixed data of an encrypted file.
6 is a flowchart illustrating a decryption process for a file to which end-to-end encryption is applied according to an embodiment of 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 embodiments described in the text. That is, since the embodiments can be variously changed and have various forms, the scope of the present invention should be understood to include 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 those effects, the scope of the present invention should not be understood as being limited thereto.

Meanwhile, the meaning of terms described in the present application should be understood as follows.

Terms such as "first" and "second" are used to distinguish one component from other components, and the scope of rights is not limited by these terms. For example, a first component may be referred to as a second component, and similarly, a second component may be referred to as a first component.

When a component is referred to as being "connected" to another component, it should be understood that although it may be directly connected to the other component, another component may exist in the middle. On the other hand, when it is mentioned that a certain component is "directly connected" to another component, it should be understood that no other component exists in the middle. On the other hand, other expressions describing the relationship between the constituent elements, that is, "between" and "just between" or "neighboring to" and "directly neighboring to" should be interpreted as well.

Singular expressions are to be understood as including plural expressions unless the context clearly indicates otherwise, and terms such as “comprise” or “have” refer to implemented features, numbers, steps, actions, components, parts, or It is to be understood that it is intended to designate that a combination exists and does not preclude the presence or addition of one or more other features or numbers, steps, actions, components, parts, or combinations thereof.

In each step, the identification code (for example, a, b, c, etc.) is used for convenience of explanation, and the identification code does not describe the order of each step, and each step has a specific sequence clearly in context. Unless otherwise stated, it may occur differently from the stated order. That is, each of the steps 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 storing data that can be read by a computer system. . Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disk, and optical data storage devices. Further, the computer-readable recording medium is distributed over a computer system connected by a network, so that the computer-readable code can 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 field to which the present invention belongs, unless otherwise defined. Terms defined in commonly used dictionaries should be construed as having meanings in the context of related technologies, and cannot be construed as having an ideal or excessive formal meaning unless explicitly defined in the present application.

1 is a diagram illustrating a configuration of a decryption system for a file to which end-to-end encryption is applied according to the present invention.

Referring to FIG. 1, a decryption system 100 for a file to which end-to-end encryption is applied may include a user terminal 110, a decryption device 130, and a database 150.

The user terminal 110 may correspond to a computing device capable of exchanging messages with a counterpart through a messenger, and may be implemented as a smartphone, a laptop computer, or a computer, and is not necessarily limited thereto, and may also be used with various devices such as a tablet PC. Can be implemented. The user terminal 110 may be connected to the decoding device 130 through a network, and a plurality of user terminals 110 may be connected to the decoding device 130 at the same time.

The decryption apparatus 130 may be implemented as a computer or a server corresponding to a program capable of decrypting important information encrypted during a message communication process between the user terminals 110. The decoding device 130 may be wirelessly connected to the user terminal 110 through Bluetooth, WiFi, a communication network, and the like, and may exchange data with the user terminal 110 through a network.

In an embodiment, the decryption device 130 may store information necessary for decrypting an encrypted file in conjunction with the database 150. Meanwhile, unlike FIG. 1, the decoding apparatus 130 may be implemented including the database 150 therein. In addition, the decoding apparatus 130 may be implemented including a processor, a memory, a user input/output unit, and a network input/output unit, which will be described in more detail with reference to FIG. 2.

The database 150 may correspond to a storage device that stores various information necessary in a process of encrypting messages exchanged between users and restoring important data based on this. The database 150 may store message information, personal information, and symmetric key information used for encryption from the user terminal 110, and is not limited thereto, and the decryption device 130 decrypts it from the encrypted file. Thus, information collected or processed in various forms can be stored in the process of recovering the original message.

FIG. 2 is a block diagram illustrating a physical configuration of the decoding apparatus in FIG. 1.

Referring to FIG. 2, the decoding apparatus 130 may include a processor 210, a memory 230, a user input/output unit 250, and a network input/output unit 270.

The processor 210 can execute each procedure for processing each operation in the process of decrypting messages between users or recovering passwords, and can manage the memory 230 that is read or written throughout the process. , It is possible to schedule a synchronization time between the volatile memory in the memory 230 and the nonvolatile memory. The processor 210 can control the overall operation of the decoding 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. have. The processor 210 may be implemented as a CPU (Central Processing Unit) of the decoding device 130.

The memory 230 may include an auxiliary memory device that is implemented as a nonvolatile memory such as a solid state drive (SSD) or a hard disk drive (HDD), and is used to store all data required for the decryption device 130, and RAM A main memory device implemented with volatile memory such as (Random Access Memory) may be included.

The user input/output unit 250 may include an environment for receiving a user input and an environment for outputting specific information to a 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 one embodiment, the user input/output unit 250 may correspond to a computing device connected through a remote connection, and in such a case, the decryption device 130 may be performed as a server.

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

3 is a block diagram illustrating a functional configuration of the decoding apparatus in FIG. 1.

3, the decryption device 130 includes a first encrypted file decryption unit 310, a second encrypted file decryption unit 330, a third encrypted file decryption unit 350, a password recovery unit 370, and a control unit. (390) may be included.

The first encrypted file decryption unit 310 may decrypt a first encrypted file storing a private key and a public key for a user account. That is, the first encrypted file decryption unit 310 may decrypt the first encrypted file to obtain a unique private key and public key for each user account. The first encrypted file decryption unit 310 may obtain original data by separating data from the first encrypted file and generating a decryption key.

In addition, the first encrypted file may have a file name of a specific format according to an application that exchanges messages between users. For example, the first encryption file may include a login ID associated with a user account as a file name. In addition, the private key and the public key can be used to generate a symmetric key, that is, a secret key used for message encryption.

The second encrypted file decryption unit 330 may decrypt a second encrypted file storing a symmetric key for encrypting a message of a user account based on the decryption result of the first encrypted file. That is, the second encrypted file decryption unit 330 may obtain a unique symmetric key for each user account by decrypting the second encrypted file. The symmetric key may correspond to a secret key used for message encryption. The second encrypted file decryption unit 330 may obtain original data by separating data from the second encrypted file and reconstructing the decryption key.

In one embodiment, the first and second encrypted files include data encrypted using a secret key each generated based on a password of a user account and at least one intermediate value, and the encrypted data is at least one It can be concatenated and stored in order with the median value of.

For example, the original data of Username.ssi (ie, the first encrypted file) may be encrypted based on the user's login password and then compressed and stored by GNU-Zip. In this case, the encryption algorithm used is AES-256-GCM and can be expressed as Equation 1 below.

[Equation 1]

Encrypted_Username.ssi = GNU-Zip(AES-256-GCM _secrets-key (Username.ssi))

The secrets-key used for encryption may be generated by concatenating a specific value to the user's login password and then rotating PBKDF2-HMAC-SHA256 1000 times, and may be expressed by Equation 2 below.

[Equation 2]

Secrets-key = PBKDF2((password||identity), salt, iter=1000, HMAC-SHA256)

Here, the iv value used in Equation 1 and the salt value used in Equation 2 are intermediate values used for encryption and may correspond to 16 bytes randomly generated, and the front part of the encrypted data after encryption is completed. It may be connected to and stored, and may be expressed as Equation 3 below.

[Equation 3]

Username.ssi = iv||salt||encrypted_Username.ssi

In addition, the original data of Secrets.sss (that is, the second encrypted file) may be encrypted and stored through an encryption process expressed as in Equations 4 to 6 below.

[Equation 4]

Encrypted_secrets.sss = AES-256-GCMsecrets-key(Secrets.sss)

[Equation 5]

Secrets-key = PBKDF2(password, salt, iter=5000, HMAC-SHA256)

[Equation 6]

Secrets.sss = iv||salt||encrypted_Secrets.sss

Accordingly, the second encrypted file may have no GNU-zip, no identity of Equation 2, and a different number of repetitions of PBKDF2 compared to the first encrypted file.

In one embodiment, the first encrypted file is concatenated with an identity value determined according to a location where the first encrypted file is stored and a password of a user account, and then repeatedly applied a hash function with at least one median value. Encrypted data may be included using the generated secret key. That is, in Equation 2, the identity value may have a different value depending on the location where data is stored. For example, if the username.ssi file is stored inside the device storage, it may correspond to identity = _cache_identity, and if it is extracted using the backup function inside the application, it may correspond to identity = _export_identity.

In one embodiment, the second encryption file includes data encrypted using a secret key generated by repeatedly applying a hash function to a password of a user account with at least one intermediate value, and the number of repeated applications is the first encryption It can be different from the number of iterations on the file. That is, the second encrypted file may generate a secret key through Equation 5, and use this to generate encrypted data through Equation 4. In particular, the number of repetitions to which the hash function is applied to generate the secret key in Equation 5 may be different from the number of repetitions applied in Equation 2.

In one embodiment, the second encrypted file decryption unit 330 is based on the private key of the user account obtained through decryption of the first encrypted file and the public key of the other party associated with the user account when the second encrypted file does not exist. The symmetric key can be obtained by applying a hash function to the median value calculated by. For example, the secret key for message encryption stored in Secrets.sss (the second encryption file) is the value of the hashed value with SHA256 after generating the public key of the other party with whom the conversation is made through the ECDH algorithm. It may correspond to, and may be expressed as Equations 7 and 8 below.

[Equation 7]

Sharing-secrets = MyPrivateKey * OtherPublicKey

[Equation 8]

Message-Enc/Decrypt-Key = SHA256 (sharing-secrets)

In one embodiment, the second encrypted file decryption unit 330 obtains a hashmap object through decryption of the second encrypted file, parses the hashmap object to determine the starting point of the key A step of obtaining a symmetric key for each user account by searching for a separator separating a key and a value may be performed.

For example, the data obtained by the second encrypted file decryption unit 330 may be generated in the form of a JAVA Hashmap Object, and the key value is a complex data such as a user id, a counterpart id, and an application version of each user. It can be configured, and the corresponding Value value can correspond to a secret key used for message encryption. The second encryption file decryption unit 330 can parse all the starting points of the keys of the JAVA Hashmap Object, find a value that separates the key and the value (for example, 0x00000020) to obtain a key used for message encryption for each user can do.

The third encrypted file decryption unit 350 may decrypt the third encrypted file storing the message of the user account based on the decryption result of the second encrypted file. That is, the third encrypted file decryption unit 350 uses the symmetric key obtained by the second encrypted file decryption unit 330 to perform decryption that operates in the reverse order of the encryption process, so that the original message sent and received by the user account You can get information about it.

For example, Message.sss (that is, the third encrypted file) is a file compressed by GNU-zip, and when decompressed, all data except for the message, Data, may exist in plain text. However, the IV value required for decoding may be Base64 Encoded and stored. The encrypted message (Data) is Base64-encoded data of (encrypted message || authenticator), and a method of obtaining the original data may be expressed as Equation 9 below.

[Equation 9]

Original-Message=AES-256-GCM _key (Base64Decode(Data), Base64Decode(IV), mode=decryption)

In an embodiment, the third encrypted file decryption unit 350 may determine the type of a message stored in the third encrypted file and obtain original data by decrypting the encrypted message according to the message type. For example, the third encrypted file decryption unit 350 may determine the message type through the MimeType variable stored in the third encrypted file.

In one embodiment, the third encrypted file decryption unit 350 downloads the encrypted message through a data link and then performs decryption when the message type is media, and the message type is GIF. In the case of (gif), the original data can be downloaded through the data link obtained as a result of decrypting the encrypted message.

More specifically, in the case of photo and voice recording, since the URL is stored in the data, the third encrypted file decryption unit 350 may perform decryption through Equation 9 after downloading the data from the corresponding URL. In this case, when the data is decrypted, the URL appears, and the original file can be obtained by downloading the data from the URL.

The password recovery unit 370 may recover the password of the user account by using the first encrypted file or the second encrypted file. For example, an encrypted Username.s or Secrets.sss is required to recover a login password, and when Username.ssi is used, recovery may be about 5 times faster than Secrets.sss.

In one embodiment, the password recovery unit 370 includes estimating a candidate password, generating a candidate key based on the estimated candidate password, applying the candidate key to an alternative encryption algorithm to encrypt a first encrypted file or a second encryption. Decrypting a specific block of the file and determining a candidate password as the password of the user account when the data obtained as a result of decrypting the specific block matches fixed data related to the first encrypted file or the second encrypted file can do. This will be described in more detail in FIG. 5.

The control unit 390 controls the overall operation of the decryption device 130, and the first encrypted file decryption unit 310, the second encrypted file decryption unit 330, the third encrypted file decryption unit 350, and the password recovery unit Control flow or data flow between 370 may be managed.

4 is a flowchart illustrating a decryption process for a file to which end-to-end encryption is applied, performed by the decryption apparatus of FIG. 1.

Referring to FIG. 4, the decryption device 130 may decrypt a first encrypted file storing a private key and a public key for a user account through the first encrypted file decryption unit 310 (step S410). The decryption device 130 may decrypt a second encrypted file storing a symmetric key for encrypting a message of a user account based on the decryption result of the first encrypted file through the second encrypted file decryption unit 330 (Step S430).

In addition, the decryption apparatus 130 may decrypt a third encrypted file storing a message of the user account based on the decryption result for the second encrypted file through the third encrypted file decryption unit 350 (step S450). . The decryption device 130 may recover the password of the user account by using the first encrypted file or the second encrypted file through the password recovery unit 370 (step S470).

5 is an exemplary diagram illustrating an embodiment of a password recovery algorithm and fixed data of an encrypted file.

Referring to FIG. 5, fixed data as illustrated in (a) of FIG. 5 may exist in the decrypted first encrypted file (Username.ssi) and the second encrypted file (Secrets.sss). AES-256-GCM, which is used to encrypt two data, is a mode created to provide both encryption and integrity guarantee at the same time, and the algorithm actually used for encryption may be the same as the AES-256-CTR mode.

Therefore, after guessing the user login password, one block (16 bytes) of the encrypted Username.ssi or Secrets.sss is decrypted using the key generated by Equation 2 or Equation 5 and the AES-256-CTR mode. If one result matches the fixed data in Figure (a), it can be seen that the correct password has been found.

However, the IV used in AES-256-CTR mode is different from the IV used in AES-256-GCM, and may correspond to the IV (Counter) value transformed through the GHASH algorithm of the IV used in AES-256-GCM. have. Figure 5 (b) may correspond to a detailed login password recovery algorithm.

6 is a flowchart illustrating a decryption process for a file to which end-to-end encryption is applied according to an embodiment of the present invention.

Referring to FIG. 6, the decoding apparatus 130 may start message decoding by selecting a message.sss file to be decoded. The decryption apparatus 130 may check whether the [Username].ssi and secret.sss files required for the data decryption operation exist and terminate the operation if none of the [Username].ssi and secret.sss files exist. If the password is not known, the decryption device 130 may recover the password in algorithm 10. Since the recovery method using [Username].ssi is more efficient, the decoding apparatus 130 may preferentially apply this method.

In addition, the decryption apparatus 130 may decrypt secret.sss based on the recovered password to recover the symmetric key used for message encryption. If there is no secret.sss, the decryption apparatus 130 may derive and recover a symmetric key through algorithms 7 and 8 based on the decrypted [Username].ssi.

Finally, the decryption apparatus 130 may obtain the original message by decrypting the data through the AES-256-GCM algorithm using the recovered symmetric key and the IV information remaining in the message. The decoding apparatus 130 may perform an additional process when it is necessary to download data from a link according to the type of media. If there is an additional missing Message ID, the decoding apparatus 130 may recover data by limiting to media data based on the cache data. In this case, the decoding apparatus 130 may recover the used IV by using the algorithm 11.

Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art will variously modify and change the present invention within the scope not departing from the spirit and scope of the present invention described in the following claims. You will understand that you can do it.

100: decryption system for files with end-to-end encryption applied
110: user terminal 130: decoding device
150: database
210: processor 230: memory
250: user input/output unit 270: network input/output unit
310: first encrypted file decryption unit 330: second encrypted file decryption unit
350: third encrypted file decryption unit 370: password recovery unit
390: control unit

Claims (11)

A first encrypted file decryption unit for decrypting a first encrypted file storing a private key and a public key for a user account;
A second encrypted file decryption unit for decrypting a second encrypted file storing a symmetric key for encrypting a message of the user account based on the decryption result of the first encrypted file; And
A third encrypted file decryption unit for decrypting a third encrypted file storing a message of the user account based on a result of decrypting the second encrypted file,
The second encrypted file decryption unit obtains a hashmap object through decryption of the second encrypted file, parsing the hashmap object to determine a starting point of a key, and A decryption apparatus for a file to which end to end encryption is applied, characterized in that performing the step of obtaining a symmetric key for each user account by searching for a separator separating a value.
The method of claim 1,
The first and second encrypted files include data encrypted using a secret key each generated based on a password of the user account and at least one intermediate value,
The decryption apparatus for a file to which end-to-end encryption is applied, wherein the encrypted data is concatenated and stored in order with the at least one intermediate value.
The method of claim 2, wherein the first encrypted file
Encrypt using a secret key generated by repetitively applying a hash function with the at least one intermediate value after concatenating an identity value determined according to the location where the first encrypted file is stored and the password of the user account A decryption device for a file to which end-to-end encryption has been applied, including the encrypted data.
The method of claim 3,
The second encrypted file includes data encrypted using a secret key generated by repeatedly applying a hash function to the password of the user account with the at least one intermediate value,
The number of times of repeated application is different from the number of times of repeated application of the first encrypted file.
The method of claim 1, wherein the second encrypted file decryption unit
If the second encrypted file does not exist, a hash function is applied to the median value calculated based on the private key of the user account obtained through decryption of the first encrypted file and the public key of the other party associated with the user account. A decryption apparatus for a file to which end-to-end encryption is applied, wherein the symmetric key is obtained.
delete The method of claim 1, wherein the third encrypted file decryption unit
A decryption apparatus for a file to which end-to-end encryption is applied, characterized in that for determining a type of message stored in the third encrypted file and decrypting the encrypted message according to the type of the message to obtain original data.
The method of claim 7, wherein the third encrypted file decryption unit
When the message type is media, decryption is performed after downloading the encrypted message through a data link,
When the type of the message is gif, the decryption apparatus for a file to which end-to-end encryption is applied, wherein the original data is downloaded through a data link obtained as a result of decrypting the encrypted message.
The method of claim 1,
The decryption apparatus for a file to which end-to-end encryption is applied, further comprising a password recovery unit for recovering a password of the user account using the first encrypted file or the second encrypted file.
The method of claim 9, wherein the password recovery unit
Estimating a candidate password;
Generating a candidate key based on the estimated candidate password;
Decoding a specific block of the first encrypted file or the second encrypted file by applying the candidate key to an alternative encryption algorithm; And
When the data obtained as a result of the decryption of the specific block coincides with the fixed data of the first encrypted file or the second encrypted file, determining the candidate password as the password of the user account. Decryption device for files with end-to-end encryption applied.
In the decryption method performed in a decryption apparatus for a file to which end to end encryption is applied,
Decrypting a first encrypted file storing a private key and a public key for a user account;
Decrypting a second encrypted file storing a symmetric key for encrypting a message of the user account based on the decryption result of the first encrypted file; And
Including the step of decrypting a third encrypted file storing the message of the user account based on the decryption result of the second encrypted file,
The decrypting the second encrypted file includes obtaining a hashmap object through decryption of the second encrypted file, parsing the hashmap object to determine a starting point of a key, and , A method for decrypting a file to which end-to-end encryption is applied, comprising the step of obtaining a symmetric key for each user account by searching for a separator separating a key and a value.

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