KR102328057B1 - Document security service server that supports encryption of document files based on terminal information and operating method thereof - Google Patents

Abstract

Disclosed are a document security service server that supports encryption of a document file based on terminal information and an operating method thereof. In the present invention, when an encryption request for a document file generated in the user terminal is received from a user terminal, an encryption key for encryption of the document file is extracted based on the device unique identification number of the user terminal and provided to the user terminal By presenting a document security service server and an operating method thereof, the user terminal supports to complete the encryption of the document file based on the device unique identification number of the user terminal, and through this, the document in the user terminal When the file is decrypted, by enabling decryption of the document file based on the device unique identification number of the user terminal, it is possible to support encryption and decryption of the document file in the user terminal without input of a separate password have.

Description

A document security service server that supports encryption of a document file based on terminal information and an operating method thereof

The present invention relates to a document security service server that supports encryption of a document file based on terminal information and an operating method thereof.

In recent years, as electronic terminals such as computers, smart phones, or tablet PCs have become widespread, various types of electronic document-related programs have been released that allow users to read, write, and edit documents using the electronic terminals.

These electronic document-related programs include a word processor supporting basic document creation and editing, a spreadsheet supporting data input, arithmetic operations, and data management, and presentation programs supporting a presenter's presentation.

Conventionally, when a user encrypts a document requiring security, by setting a predetermined password on the document, a person who does not know the password has been restricted from reading or modifying the document.

However, when the document is encrypted by using the password in this way, the inconvenience of having to input the password every time the user reads the document may occur.

In addition, if the user forgets the password set in the document, there may be a problem that the document cannot be read.

In general, documents requiring security are often designated so that they can be read only in a specific electronic terminal that is permitted to read the document, not in several electronic terminals.

In this way, when document reading is permitted only in a specific electronic terminal, the MAC address of the specific electronic terminal or, if the specific electronic terminal is a mobile terminal, based on a unique identification number such as an international mobile device identification code or phone number of the corresponding electronic terminal It is possible to configure a system that enables encryption and decryption of documents.

In this way, when a system enabling encryption and decryption of a document based on a unique identification number of a specific electronic terminal is introduced, when a user reads a document in the specific electronic terminal, even if a separate password is not input Since the decryption of the document can be performed based on the identification number, the user will be able to more easily read the secured document without having to remember the password for decrypting the document or input the password.

In the present invention, when an encryption request for a document file generated in the user terminal is received from a user terminal, an encryption key for encryption of the document file is extracted based on the device unique identification number of the user terminal and provided to the user terminal By presenting a document security service server and an operating method thereof, the user terminal supports to complete the encryption of the document file based on the device unique identification number of the user terminal, and through this, the document in the user terminal To support encryption and decryption of the document file in the user terminal without input of a separate password by enabling decryption of the document file based on the device unique identification number of the user terminal when the file is decrypted do.

A document security service server supporting encryption of a document file based on terminal information according to an embodiment of the present invention includes n different (n is a natural number greater than or equal to 2) composed of a public key and a private key corresponding to the public key. When an encryption request signal for a document file generated in the first user terminal is received from a key pair storage unit in which key pairs are stored, and a first user terminal among a plurality of user terminals, the first user terminal is sent to the first user terminal. An encryption information requesting unit for requesting transmission of a device-specific identification number to a user terminal, when a first device-specific identification number is received from the first user terminal, from the key pair storage unit based on the first device-specific identification number A public key extraction unit for extracting a first public key constituting a first key pair, which is one of the n key pairs, and when the first public key is extracted, transmits the first public key to the first user terminal At the same time, an encryption information transmission unit for transmitting an encryption command instructing to encrypt the document file with the first public key to the first user terminal and when encryption of the document file is completed in the first user terminal, the and an encryption message receiving unit for receiving an encryption completion message indicating that encryption of the document file is completed from the first user terminal.

In addition, the operating method of the document security service server supporting the encryption of a document file based on terminal information according to an embodiment of the present invention is different n (n is a public key and a private key corresponding to the public key) 2 or more) maintaining a key pair storage unit in which key pairs are stored, when an encryption request signal for a document file generated in the first user terminal is received from a first user terminal among a plurality of user terminals, the requesting transmission of a device-specific identification number for the first user terminal to a first user terminal; when a first device-specific identification number is received from the first user terminal, based on the first device-specific identification number extracting a first public key constituting a first key pair that is any one of the n key pairs from a key pair storage unit; when the first public key is extracted, the first public key is transferred to the first user terminal at the same time as transmitting to the first user terminal, transmitting an encryption command instructing to encrypt the document file with the first public key, and when encryption of the document file is completed in the first user terminal, the second and receiving an encryption completion message indicating that encryption of the document file is completed from a user terminal.

In the present invention, when an encryption request for a document file generated in the user terminal is received from a user terminal, an encryption key for encryption of the document file is extracted based on the device unique identification number of the user terminal and provided to the user terminal By presenting a document security service server and an operating method thereof, the user terminal supports to complete the encryption of the document file based on the device unique identification number of the user terminal, and through this, the document in the user terminal When the file is decrypted, by enabling decryption of the document file based on the device unique identification number of the user terminal, it is possible to support encryption and decryption of the document file in the user terminal without input of a separate password have.

1 is a diagram showing the structure of a document security service server according to an embodiment of the present invention.
2 is a flowchart illustrating a method of operating a document security service server according to an embodiment of the present invention.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings. These descriptions are not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. While describing each drawing, like reference numerals are used for similar components, and unless otherwise defined, all terms used in this specification, including technical or scientific terms, refer to those of ordinary skill in the art to which the present invention belongs. It has the same meaning as is commonly understood by those who have it.

In this document, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated. In addition, in various embodiments of the present invention, each of the components, functional blocks or means may be composed of one or more sub-components, and the electrical, electronic, and mechanical functions performed by each component are electronic. A circuit, an integrated circuit, an ASIC (Application Specific Integrated Circuit), etc. may be implemented with various well-known devices or mechanical elements, and may be implemented separately or two or more may be integrated into one.

On the other hand, the blocks in the accompanying block diagram or steps in the flowchart are computer program instructions that are loaded in a processor or memory of equipment capable of data processing, such as a general-purpose computer, a special-purpose computer, a portable notebook computer, and a network computer, and perform specified functions. can be interpreted as meaning Since these computer program instructions may be stored in a memory provided in a computer device or in a memory readable by a computer, the functions described in the blocks of the block diagrams or the steps of the flowcharts are produced as articles of manufacture containing instruction means for performing the same. could be In addition, each block or each step may represent a module, segment, or portion of code comprising one or more executable instructions for executing the specified logical function(s). It should also be noted that, in some alternative embodiments, it is also possible for the functions recited in blocks or steps to be executed out of the prescribed order. For example, two blocks or steps shown one after another may be performed substantially simultaneously or in the reverse order, and in some cases, some blocks or steps may be omitted.

1 is a diagram illustrating a structure of a document security service server that supports encryption of a document file based on terminal information according to an embodiment of the present invention.

The document security service server 110 according to the present invention includes a key pair storage unit 111 , an encryption information request unit 112 , a public key extraction unit 113 , an encryption information transmission unit 114 , and an encryption message reception unit 115 . includes

In the key pair storage unit 111, n different (n is a natural number greater than or equal to 2) key pairs composed of a public key and a private key corresponding to the public key are stored.

At this time, according to an embodiment of the present invention, in the key pair storage unit 111, for each of the n key pairs, preset different integer values of 0 or more and n-1 or less corresponding to each of the n key pairs This may be additionally stored in correspondence.

For example, if it is assumed that 'n=5', the key pair storage unit 111 contains five key pairs and 'different integer values between 0 and 4' corresponding to each key pair as shown in Table 1 below. Information may be stored.

5 key pairs integer value public key 1 - private key 1 0 public key 2 - private key 2 One public key 3 - private key 3 2 public key 4 - private key 4 3 public key 5 - private key 5 4

The encryption information request unit 112 receives an encryption request signal for the document file generated in the first user terminal 101 from the first user terminal 101 among the plurality of user terminals 101 , 102 , 103 , 104 . If it is, it requests transmission of the device-specific identification number for the first user terminal 101 to the first user terminal 101 .

Here, the device-specific identification number is a MAC address (Media Access Control Address), if the plurality of user terminals 101, 102, 103, 104 is a mobile terminal, an International Mobile Equipment Identity or each user terminal means a phone number assigned to

When the first device-specific identification number is received from the first user terminal 101, the public key extraction unit 113 receives the first device-specific identification number from among the n key pairs from the key pair storage unit 111 based on the first device-specific identification number. Extracts the first public key constituting any one of the first key pair.

At this time, according to an embodiment of the present invention, when the public key extraction unit 113 receives the first device-specific identification number from the first user terminal 101, the first device-specific identification number is an integer of a decimal number. Converting to a first integer value, and performing a modulo operation of dividing the first integer value as a dividend by n as a divisor, thereby calculating a first operation value, and storing the first value from the key pair storage 111 After selecting the first key pair corresponding to the operation value, the first public key may be extracted from the first key pair.

Here, the modulo operation refers to an operation of dividing a dividend by a divisor to calculate a remainder thereof.

For example, it is assumed that 'n=5' and the first device unique identification number is a MAC address such as '1A:00:3F:F1:4C:C5'. Usually, since the MAC address is a hexadecimal number, the public key extraction unit 113 performs the first device unique identification number '1A:00:3F:F1:4C:C5' to the hexadecimal number '1A003FF14CC5'. ' can be converted to '28588375100613', which is the first integer value of a decimal number.

Thereafter, the public key extraction unit 113 may calculate a first calculated value of '3' by performing a modulo operation of dividing 5 as a divisor of the first integer value '28588375100613'.

Then, the public key extraction unit 113 selects the first key pair 'public key 4 - private key 4' corresponding to the first operation value '3' from the key pair storage unit 111 as shown in Table 1 above. Thereafter, 'public key 4' may be extracted from the first key pair 'public key 4 - private key 4' as the first public key.

In this way, when the first public key is extracted by the public key extracting unit 113 , the encryption information transmitting unit 114 transmits the first public key to the first user terminal 101 and at the same time as the document file transmits an encryption command instructing to encrypt with the first public key to the first user terminal 101 .

At this time, when the first public key and the encryption command are received from the document security service server 110 , the first user terminal 101 encrypts the document file based on the first public key and then An encryption completion message indicating that encryption is completed may be transmitted to the document security service server 110 .

In this case, the encryption message receiving unit 115 receives the encryption completion message transmitted from the first user terminal 101 as the encryption of the document file is completed in the first user terminal 101 .

That is, the document security service server 110 stores different key pairs composed of a public key and a private key corresponding to the public key in the key pair storage unit 111, and the plurality of user terminals 101, 102, When an encryption request signal for the document file generated in the first user terminal 101 is received from the first user terminal 101 among 103 and 104 , the first user terminal 101 sends the first user terminal 101 to the first user terminal 101 . When a device-specific identification number is requested to be transmitted, and a first device-specific identification number is received from the first user terminal 101, the first key from the key pair storage unit 111 based on the first device-specific identification number The first user extracts the first public key constituting the pair, transmits the first public key to the first user terminal 101, and at the same time sends an encryption command instructing to encrypt the document file with the first public key By transmitting to the terminal 101 , it is possible to support the document file to be encrypted in the first user terminal 101 based on the device-specific identification number of the first user terminal 101 .

According to an embodiment of the present invention, the document security service server 110 further includes a decryption information request unit 116 , a private key extractor 117 , a decryption information transmitter 118 , and a decryption message receiver 119 . can do.

After receiving the encryption completion message from the first user terminal 101 , the decryption information requesting unit 116 receives the encrypted document file from the first user terminal 101 as the encrypted document file is executed. When the decryption request signal for the encrypted document file is received, the transmission of the device-specific identification number to the first user terminal 101 is requested to the first user terminal 101 .

When the first device-specific identification number is received from the first user terminal 101, the private key extraction unit 117 converts the first device-specific identification number into the first integer value that is an integer of a decimal number, and the second By performing a modulo operation in which an integer value is a dividend and n is a divisor, the first operation value is calculated, and the first key pair corresponding to the first operation value is selected from the key pair storage unit 111 . Then, a first private key is extracted from the first key pair.

When the first private key is extracted, the decryption information transmission unit 118 transmits the first private key to the first user terminal 101 and at the same time instructs to decrypt the encrypted document file with the first private key. transmits a decryption command to the first user terminal 101 .

When the decryption of the document file encrypted by the first user terminal 101 is completed, the decryption message receiving unit 119 indicates that the decryption of the encrypted document file from the first user terminal 101 is completed. receive a message

Hereinafter, operations of the decryption information request unit 116 , the private key extractor 117 , the decryption information transmitter 118 , and the decryption message receiver 119 will be described in detail with an example.

First, as in the example described above, it is assumed that 'n=5' and the first device unique identification number is '1A:00:3F:F1:4C:C5'.

At this time, after the encryption completion message is received from the first user terminal 101 to the document security service server 110 , as the encrypted document file is executed in the first user terminal 101 , the first user terminal 101 ), when a decryption request signal for the encrypted document file is received from the document security service server 110 , the decryption information request unit 116 sends the first user terminal 101 to the first user terminal 101 You can request transmission of a unique identification number.

At this time, when '1A:00:3F:F1:4C:C5', which is the first device unique identification number, is received from the first user terminal 101 to the document security service server 110, the private key extraction unit 117 can convert '1A003FF14CC5', which is a hexadecimal number, from '1A:00:3F:F1:4C:C5', which is the first device unique identification number, to '28588375100613', which is a first integer value of a decimal number.

Thereafter, the private key extraction unit 117 may calculate the first calculated value '3' by performing a modulo operation of dividing 5 as a divisor of the first integer value '28588375100613'.

Then, the private key extraction unit 117 extracts the first key pair 'public key 4 - private key 4' corresponding to the first operation value '3' from the key pair storage unit 111 as shown in Table 1 above. After selection, the first private key 'private key 4' may be extracted from the first key pair 'public key 4 - private key 4'.

In this way, when the 'private key 4' which is the first private key is extracted by the private key extraction unit 117, the decryption information transmission unit 118 converts the 'private key 4' which is the first private key to the first user terminal. At the same time as transmitting to 101 , a decryption command instructing to decrypt the encrypted document file using the 'private key 4', which is the first private key, may be transmitted to the first user terminal 101 .

In this way, when the 'private key 4' which is the first private key and the decryption command are transmitted to the first user terminal 101 by the decryption information transmission unit 118, the first user terminal 101 transmits the first After receiving the 'private key 4' which is the private key and the decryption command, the document file is decrypted based on the 'private key 4' which is the first private key, and then the decryption completion indicating that the decryption of the document file is completed The message may be transmitted to the document security service server 110 .

In this case, the decryption message receiver 119 may receive the decryption completion message transmitted from the first user terminal 101 as the decryption of the document file is completed in the first user terminal 101 .

As a result, the document security service server 110 according to the present invention completes the encryption of the document file in the first user terminal 101 with the first public key extracted based on the device-specific identification number of the first user terminal 101 . Thereafter, when a request to decrypt the document file is received from the first user terminal 101 as the document file is executed from the first user terminal 101 , based on the device unique identification number of the first user terminal 101 , By extracting the first private key corresponding to the first public key and providing it to the first user terminal 101, the document file is automatically decrypted in the first user terminal 101 without entering a separate password. can support you to become

According to an embodiment of the present invention, after the document security service server 110 completes encryption of a document file in a specific user terminal, the user of the specific user terminal wants to transfer the decryption right for the document file to another user terminal. In this case, the method may further include a configuration for allowing the decryption right for the document file to be transferred from the specific user terminal to another user terminal.

In this regard, the document security service server 110 according to the present invention includes an information requesting unit 120, a decrypting unit 121, a terminal information requesting unit 122, an additional key extracting unit 123, and a document file transmitting unit ( 124) may be further included.

When the information requesting unit 120 receives a transmission request signal requesting to transmit the encrypted document file to the second user terminal 102 from the first user terminal 101, the encrypted document file to the first user terminal 101 is received. It requests transmission of the document file and the device-specific identification number to the first user terminal 101 .

When the encrypted document file and the first device-specific identification number are received from the first user terminal 101, the decryption unit 121 converts the first device-specific identification number into the first integer value that is an integer of a decimal number. and, by performing a modulo operation in which the first integer value is a dividend and n as a divisor, the first operation value is calculated, and the first operation value corresponding to the first operation value is obtained from the key pair storage unit 111 . After selecting a key pair, the first private key is extracted from the first key pair, and the encrypted document file is decrypted with the first private key.

The terminal information requesting unit 122 attempts a communication connection with the second user terminal 102 , and when the communication connection with the second user terminal 102 is established, the second user terminal 102 is sent to the second user terminal. Request the transmission of the device unique identification number to (102).

When the second device-specific identification number is received from the second user terminal 102 , the additional key extraction unit 123 converts the second device-specific identification number into a second integer value that is an integer of a decimal number, and the second integer A second operation value is calculated by performing a modulo operation in which a value is a dividend and n is a divisor, and after selecting a second key pair corresponding to the second operation value from the key pair storage unit 111 , the second A second public key is extracted from the key pair.

When the second public key is extracted, the document file transfer unit 124 re-encrypts the decrypted document file with the second public key and then transmits the re-encrypted document file to the second user terminal 102 .

Hereinafter, operations of the information request unit 120 , the decryption unit 121 , the terminal information request unit 122 , the additional key extraction unit 123 , and the document file transfer unit 124 will be described in detail with an example. .

First, as in the example described above, 'n=5', the first device-specific identification number is '1A:00:3F:F1:4C:C5', and the second device-specific identification number is '2C: Assume 4B:00:A1:3C:E7'.

At this time, when a transmission request signal requesting to transmit the encrypted document file to the document security service server 110 from the first user terminal 101 is received to the second user terminal 102, the information requesting unit 120 is The transmission of the encrypted document file and the device-specific identification number to the first user terminal 101 may be requested to the first user terminal 101 .

At this time, when the document file encrypted in the document security service server 110 and '1A:00:3F:F1:4C:C5', which is the first device-specific identification number, are received from the first user terminal 101, the decryption The unit 121 converts '1A003FF14CC5', which is a hexadecimal number, from '1A:00:3F:F1:4C:C5', which is the first device unique identification number, to '28588375100613', which is the first integer value of a decimal number. can

Thereafter, the decoder 121 may calculate the first calculated value '3' by performing a modulo operation of dividing 5 as a divisor on the first integer value '28588375100613'.

Then, the decryption unit 121 selects the first key pair 'public key 4 - private key 4' corresponding to the first operation value '3' from the key pair storage unit 111 as shown in Table 1 above. The first private key, 'private key 4', is extracted from the first key pair 'public key 4 - private key 4', and the encrypted document file can be decrypted with the first private key 'private key 4'. have.

Thereafter, the terminal information requesting unit 122 attempts a communication connection with the second user terminal 102 , and when the communication connection with the second user terminal 102 is established, the second user terminal 102 is 2 It is possible to request transmission of a device-specific identification number to the user terminal 102 .

At this time, when the second device unique identification number '2C:4B:00:A1:3C:E7' is received from the second user terminal 102 to the document security service server 110, the additional key extraction unit 123 is In the second device unique identification number '2C:4B:00:A1:3C:E7', '2C4B00A13CE7', which is a hexadecimal number, may be converted into '48700644736231', which is a second integer value of a decimal number.

Then, the additional key extractor 123 may calculate the second operation value '1' by performing a modulo operation of dividing 5 as a divisor of the second integer value '48700644736231'.

After that, the additional key extraction unit 123 selects the second key pair 'public key 2 - private key 2' corresponding to the second operation value '1' from the key pair storage unit 111 as shown in Table 1 above. Afterwards, the second public key 'public key 2' may be extracted from the second key pair 'public key 2 - private key 2'.

In this way, when the 'public key 2' which is the second public key is extracted by the additional key extraction unit 123, the document file transfer unit 124 transmits the decrypted document file to the 'public key 2' which is the second public key. After re-encrypting with ', the re-encrypted document file may be transmitted to the second user terminal 102 .

In this way, after the re-encrypted document file is transmitted to the second user terminal 102, as the re-encrypted document file is executed in the second user terminal 102, the document security service from the second user terminal 102 When a decryption request signal for the re-encrypted document file is received by the server 110 , the decryption information requesting unit 116 sends the second user terminal 102 to the device-specific identification number for the second user terminal 102 . You can request a transfer.

At this time, when the second device unique identification number '2C:4B:00:A1:3C:E7' is received from the second user terminal 102 to the document security service server 110, the private key extraction unit 117 may convert '2C4B00A13CE7', which is a hexadecimal number, from '2C:4B:00:A1:3C:E7', which is the second device unique identification number, to '48700644736231', which is the second integer value of a decimal number.

Thereafter, the private key extraction unit 117 may calculate the second calculated value '1' by performing a modulo operation of dividing 5 as a divisor of the second integer value '48700644736231'.

Then, the private key extraction unit 117 extracts the second key pair 'public key 2 - private key 2' corresponding to the second operation value '1' from the key pair storage unit 111 as shown in Table 1 above. After selection, the second private key 'private key 2' may be extracted from the second key pair 'public key 2 - private key 2'.

In this way, when the 'private key 2' which is the second private key is extracted by the private key extraction unit 117, the decryption information transmission unit 118 converts the 'private key 2' which is the second private key to the second user terminal. Simultaneously with the transmission to 102 , a decryption command instructing to decrypt the re-encrypted document file with the second private key 'private key 2' may be transmitted to the second user terminal 102 .

In this way, when the 'private key 2' which is the second private key and the decryption command are transmitted to the second user terminal 102 by the decryption information transmitting unit 118, the second user terminal 102 is the second user terminal 102 After receiving the 'private key 2' which is the private key and the decryption command, and decrypting the document file based on the 'private key 2' which is the second private key, decryption complete indicating that the decryption of the document file is completed The message may be transmitted to the document security service server 110 .

In this case, the decryption message receiving unit 119 may receive the decryption completion message transmitted from the second user terminal 102 as the decryption of the document file is completed in the second user terminal 102 .

After all, the document security service server 110 according to the present invention completes encryption of the document file in the first user terminal 101 with the first public key extracted based on the device unique identification number of the first user terminal 101 . , when the user of the first user terminal 101 wants to transfer the decryption authority for the document file to the second user terminal 102 , the decryption authority for the document file is transferred from the first user terminal 101 to the second user terminal 101 . It may support to be delivered to the user terminal 102 .

According to an embodiment of the present invention, after the document file is encrypted based on the device unique identification number of the specific user terminal, the document security service server 110 determines that the user of the specific user terminal is a user other than the specific user terminal. When the terminal wants to read the encrypted document file, the other user terminal may further include a configuration for enabling the reading of the document file.

In this regard, the document security service server 110 according to an embodiment of the present invention includes a first password request unit 125 , a document file request unit 126 , a hash value generator 127 , a recording unit 128 , It may further include an event generating unit 129 , a second password requesting unit 130 , an identification number extracting unit 131 , an auxiliary decryption processing unit 132 , and an auxiliary decryption completion message receiving unit 133 .

After the encryption completion message is received from the first user terminal 101, the first password request unit 125 enables password-based auxiliary decryption of the encrypted document file from the first user terminal 101. When a password setting request signal is received, the first user terminal 101 requests transmission of a password to be used for auxiliary decryption of the encrypted document file.

When the first password is received from the first user terminal 101 , the document file request unit 126 requests transmission of the encrypted document file to the first user terminal 101 .

When the encrypted document file is received from the first user terminal 101 , the hash value generator 127 applies the encrypted document file to a preset hash function as an input to generate a first hash value.

The recording unit 128 associates the first hash value with the first device unique identification number and the first password and records it in the password table.

After the first hash value, the first device unique identification number, and the first password are recorded in the password table, the event generating unit 129 is configured not to the first user terminal 101 but to the third user terminal 103 . ), when a decryption failure message indicating that decryption of the encrypted document file has failed is received from the third user terminal 103 as the encrypted document file is executed, auxiliary decryption of the encrypted document file is performed event to be triggered.

When the event occurs, the second password request unit 130 requests the third user terminal 103 to transmit the encrypted document file and a password for auxiliary decryption of the encrypted document file.

When the encrypted document file and the second password are received from the third user terminal 103, the identification number extraction unit 131 applies the encrypted document file as an input to the hash function to generate the first hash value. and extracts the first password recorded in correspondence with the first hash value from the password table, and checks whether the first password is the same as the second password, so that the first password is the same as the second password If confirmed, the first device unique identification number recorded corresponding to the first hash value is extracted from the password table.

When the first device-specific identification number is extracted from the password table, the auxiliary decryption processing unit 132 converts the first device-specific identification number into the first integer value that is an integer of a decimal number, and then converts the first integer value to the dividend By performing a modulo operation in which n is a divisor, the first operation value is calculated, and after selecting the first key pair corresponding to the first operation value from the key pair storage unit 111 , the first key The first private key is extracted from the pair, and when the first private key is extracted, the first private key is transmitted to the third user terminal 103 and, at the same time, the encrypted document file is transferred to the first private key. A decryption command instructing to decrypt is transmitted to the third user terminal 103 .

The auxiliary decryption completion message receiving unit 133 indicates that when the decryption of the document file encrypted by the third user terminal 103 is completed, the decryption of the encrypted document file from the third user terminal 103 is completed. Receive a decryption completion message.

Hereinafter, the first password requesting unit 125, the document file requesting unit 126, the hash value generating unit 127, the recording unit 128, the event generating unit 129, the second password requesting unit 130, the identification number Operations of the extraction unit 131 , the auxiliary decryption processing unit 132 , and the auxiliary decryption completion message receiving unit 133 will be described in detail with an example.

First, as in the example described above, it is assumed that 'n=5' and the first device unique identification number is '1A:00:3F:F1:4C:C5'.

At this time, after the encryption completion message is received from the first user terminal 101 to the document security service server 110 , the document file encrypted from the first user terminal 101 to the document security service server 110 is When a password setting request signal for enabling password-based auxiliary decryption is received, the first password request unit 125 requests transmission of a password to be used for auxiliary decryption of the encrypted document file to the first user terminal 101 . can

At this time, when 'Connection01234' is received as the first password from the first user terminal 101 to the document security service server 110 , the document file request unit 126 sends the document file encrypted by the first user terminal 101 . may request to be sent.

At this time, when the encrypted document file is received from the first user terminal 101 to the document security service server 110, the hash value generator 127 applies the encrypted document file as an input to the hash function, A first hash value such as '42d103c620a31345ag57qat327891717' may be generated.

After that, the recording unit 128 corresponds to the first hash value '42d103c620a31345ag57qat327891717', the first device unique identification number '1A:00:3F:F1:4C:C5', and the first password 'Connection01234' It can be recorded in the password table as shown in Table 2 below.

hash value Device unique identification number password 42d103c620a31345ag57qat327891717 1A:00:3F:F1:4C:C5 Connection01234

In this way, by the recording unit 128, the first hash value '42d103c620a31345ag57qat327891717', the first device unique identification number '1A:00:3F:F1:4C:C5', and the first password 'Connection01234' are stored in the table After completion of recording in the password table such as 2, as the encrypted document file is executed in the third user terminal 103 rather than the first user terminal 101, the When a decryption failure message indicating that decryption of the encrypted document file has failed is received at 110 ), the event generator 129 may generate an event for performing auxiliary decryption of the encrypted document file.

At this time, when the event is generated by the event generating unit 129 , the second password requesting unit 130 provides a password for auxiliary decryption of the encrypted document file and the encrypted document file by the third user terminal 103 . may request to be sent.

At this time, as the second password of 'Connection01234' is input to the third user terminal 103 by the user, the document file encrypted from the third user terminal 103 to the document security service server 110 and 'Connection01234' ', the identification number extraction unit 131 applies the encrypted document file as an input to the hash function to generate the first hash value '42d103c620a31345ag57qat327891717'.

After that, the identification number extraction unit 131 extracts the first password 'Connection01234' recorded in correspondence with the first hash value '42d103c620a31345ag57qat327891717' from the password table as shown in Table 2, and the first password is By confirming that 'Connection01234' is the same as 'Connection01234', which is the second password, from the password table shown in Table 2 above, '1A, which is the first device unique identification number, is recorded in correspondence to '42d103c620a31345ag57qat327891717', which is the first hash value. :00:3F:F1:4C:C5' can be extracted.

In this way, when '1A:00:3F:F1:4C:C5', which is the first device-specific identification number, is extracted from the password table as shown in Table 2 by the identification number extraction unit 131, the auxiliary decryption processing unit 132 can convert '1A003FF14CC5', which is a hexadecimal number, from '1A:00:3F:F1:4C:C5', which is the first device unique identification number, to '28588375100613', which is a first integer value of a decimal number.

Thereafter, the auxiliary decoding processing unit 132 may calculate the first operation value '3' by performing a modulo operation of dividing 5 as a divisor of the first integer value '28588375100613'.

Then, the auxiliary decryption processing unit 132 selects the first key pair 'public key 4 - private key 4' corresponding to the first operation value '3' from the key pair storage unit 111 as shown in Table 1 above. Thereafter, the 'private key 4' as the first private key may be extracted from the 'public key 4 - the private key 4' which is the first key pair.

After that, the auxiliary decryption processing unit 132 transmits the 'private key 4', which is the first private key, to the third user terminal 103, and simultaneously transmits the encrypted document file to the 'private key' as the first private key. A decoding command instructing to decode 4' may be transmitted to the third user terminal 103 .

At this time, the third user terminal 103 receives the first private key 'private key 4' and the decryption command from the document security service server 110, and based on the first private key 'private key 4' After decrypting the document file, a decryption completion message indicating that the decryption of the document file is completed may be transmitted to the document security service server 110 .

In this case, the auxiliary decryption completion message receiving unit 133 may receive the decryption completion message transmitted from the third user terminal 103 upon completion of the decryption of the document file in the third user terminal 103 .

That is, the document security service server 110 according to the present invention generates a predetermined password for auxiliary decryption for the document file after encryption of the document file is completed based on the device-specific identification number of the first user terminal 101 . By supporting setting, the document file is executed in the third user terminal 103 instead of the first user terminal 101, and the device unique identification number of the third user terminal 103 is used for encryption of the document file When the decryption of the document file fails due to a difference from the device-specific identification number, it is possible to support the user to browse the document file in the third user terminal 103 based on the password.

2 is a flowchart illustrating a method of operating a document security service server that supports encryption of a document file based on terminal information according to an embodiment of the present invention.

In step S210, a key pair storage unit in which n different (n is a natural number greater than or equal to 2) key pairs composed of a public key and a private key corresponding to the public key is stored is maintained.

In step S220, when an encryption request signal for the document file generated in the first user terminal is received from a first user terminal among a plurality of user terminals, the device specific to the first user terminal is transmitted to the first user terminal. Request transmission of identification number.

In step S230, when a first device-specific identification number is received from the first user terminal, a first key pair that is any one of the n key pairs from the key pair storage unit based on the first device-specific identification number Extracts the first public key constituting the .

In step S240, when the first public key is extracted, the first public key is transmitted to the first user terminal and, at the same time, an encryption command instructing to encrypt the document file with the first public key is transmitted to the first transmitted to the user terminal.

In step S250, when the encryption of the document file is completed in the first user terminal, an encryption completion message indicating that the encryption of the document file is completed is received from the first user terminal.

At this time, according to an embodiment of the present invention, for each of the n key pairs, preset different integer values of 0 or more and n-1 or less corresponding to each of the n key pairs are added to the key pair storage unit may be stored in correspondence with .

At this time, in step S230, when the first device-specific identification number is received from the first user terminal, the first device-specific identification number is converted into a first integer value that is an integer of a decimal number, and the first integer value is A first operation value is calculated by performing a modulo operation in which n is a divisor of n as a dividend, and after selecting the first key pair corresponding to the first operation value from the key pair storage unit, in the first key pair The first public key may be extracted.

At this time, according to an embodiment of the present invention, in the method of operating the document security service server, after the encryption completion message is received from the first user terminal, the encrypted document file is executed in the first user terminal. When a decryption request signal for the encrypted document file is received from the first user terminal, requesting transmission of a device-specific identification number for the first user terminal to the first user terminal, from the first user terminal When the first device-specific identification number is received, the first device-specific identification number is converted into the first integer value that is an integer of a decimal number, and a modulo operation is performed in which the first integer value is divided by n as a dividend. calculating the first calculated value, selecting the first key pair corresponding to the first calculated value from the key pair storage unit, and then extracting a first private key from the first key pair; When one private key is extracted, the first private key is transmitted to the first user terminal, and a decryption command instructing to decrypt the encrypted document file with the first private key is transmitted to the first user terminal and when the decryption of the document file encrypted by the first user terminal is completed, receiving a decryption completion message indicating that the decryption of the encrypted document file is completed from the first user terminal can

At this time, according to an embodiment of the present invention, in the method of operating the document security service server, when a transmission request signal requesting to transmit the encrypted document file to the second user terminal is received from the first user terminal, the first 1 requesting transmission of the encrypted document file and the device-specific identification number to the first user terminal to a user terminal, when the encrypted document file and the first device-specific identification number are received from the first user terminal , converting the first device unique identification number into the first integer value that is an integer of a decimal number, and performing a modulo operation in which the first integer value is divided by n as a dividend to calculate the first calculated value, , After selecting the first key pair corresponding to the first operation value from the key pair storage unit, extracting the first private key from the first key pair to decrypt the encrypted document file with the first private key Step, attempting a communication connection with the second user terminal, and when the communication connection with the second user terminal is established, requesting transmission of a device-specific identification number for the second user terminal to the second user terminal step, when a second device-specific identification number is received from the second user terminal, the second device-specific identification number is converted into a second integer value that is an integer of a decimal number, and the second integer value is converted to a dividend by n as a divisor by performing a modulo operation to calculate a second operation value, select a second key pair corresponding to the second operation value from the key pair storage unit, and then extract a second public key from the second key pair and when the second public key is extracted, re-encrypting the decrypted document file with the second public key and then transmitting the re-encrypted document file to the second user terminal.

In addition, according to an embodiment of the present invention, the method of operating the document security service server is based on a password for the document file encrypted from the first user terminal after the encryption completion message is received from the first user terminal When a password setting request signal is received to enable auxiliary decryption of when received, requesting transmission of the encrypted document file to the first user terminal; when the encrypted document file is received from the first user terminal, applying the encrypted document file as an input to a preset hash function generating a first hash value, the first hash value and the first device unique identification number and the first password are matched and recorded in a password table, the first hash value and the first device unique identification After the number and the first password are recorded in the password table, the encrypted document file is executed from the third user terminal as the encrypted document file is executed in the third user terminal, not the first user terminal. When a decryption failure message indicating that decryption has failed is received, generating an event for performing auxiliary decryption of the encrypted document file; when the event occurs, the encrypted document file and requesting transmission of a password for auxiliary decryption of the encrypted document file; when the encrypted document file and the second password are received from the third user terminal, applying the encrypted document file as input to the hash function to generate the first hash value, extract the first password recorded corresponding to the first hash value from the password table, check whether the first password is the same as the second password, and The password is the second password and If it is confirmed that they are the same, extracting the first device-specific identification number recorded in correspondence with the first hash value from the password table. When the first device-specific identification number is extracted from the password table, the first After converting the device-specific identification number into the first integer value, which is an integer of a decimal number, a modulo operation is performed by dividing the first integer value by n as a dividend to calculate the first operation value, and the key pair After selecting the first key pair corresponding to the first operation value from a storage unit, the first private key is extracted from the first key pair, and when the first private key is extracted, the first private key is At the same time as transmitting to a third user terminal, transmitting a decryption command instructing to decrypt the encrypted document file with the first private key to the third user terminal and to the document file encrypted by the third user terminal The method may further include receiving a decryption completion message indicating that decryption of the encrypted document file is completed from the third user terminal when the decryption is completed.

Above, an operation method of the document security service server according to an embodiment of the present invention has been described with reference to FIG. 2 . Here, since the method of operating the document security service server according to an embodiment of the present invention may correspond to the configuration of the operation of the document security service server 110 described with reference to FIG. 1 , a more detailed description thereof will be omitted. do it with

The method of operating a document security service server according to an embodiment of the present invention may be implemented as a computer program stored in a storage medium for execution through combination with a computer.

In addition, the method of operating a document security service server according to an embodiment of the present invention may be implemented in the form of a program command that can be executed through various computer means and recorded in a computer readable medium. The computer-readable medium may include program instructions, data files, data structures, etc. alone or in combination. The program instructions recorded on the medium may be specially designed and configured for the present invention, or may be known and available to those skilled in the art of computer software. Examples of the computer-readable recording medium include magnetic media such as hard disks, floppy disks and magnetic tapes, optical media such as CD-ROMs and DVDs, and magnetic such as floppy disks. - includes magneto-optical media, and hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include not only machine language codes such as those generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter or the like.

As described above, the present invention has been described with specific matters such as specific components and limited embodiments and drawings, but these are provided to help a more general understanding of the present invention, and the present invention is not limited to the above embodiments. , various modifications and variations are possible from these descriptions by those of ordinary skill in the art to which the present invention pertains.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and not only the claims to be described later, but also all those with equivalent or equivalent modifications to the claims will be said to belong to the scope of the spirit of the present invention. .

110: document security service server
111: key pair storage unit 112: encryption information request unit
113: public key extraction unit 114: encryption information transmission unit
115: encryption message receiving unit 116: decryption information request unit
117: private key extraction unit 118: decryption information transmission unit
119: decoding message receiving unit 120: information requesting unit
121: decryption unit 122: terminal information request unit
123: additional key extraction unit 124: document file delivery unit
125: first password request unit 126: document file request unit
127: hash value generator 128: record
129: event generating unit 130: second password request unit
131: identification number extraction unit 132: auxiliary decoding processing unit
133: auxiliary decryption complete message receiving unit
101: first user terminal
102: second user terminal
103: third user terminal
101, 102, 103, 104: a plurality of user terminals

Claims (12)

a key pair storage unit in which n different (n is a natural number greater than or equal to 2) key pairs composed of a public key and a private key corresponding to the public key are stored;
When an encryption request signal for the document file generated in the first user terminal is received from a first user terminal among a plurality of user terminals, transmission of a device-specific identification number for the first user terminal to the first user terminal is performed. a requesting encryption information request unit;
When a first device-specific identification number is received from the first user terminal, the first device constituting a first key pair that is any one of the n key pairs from the key pair storage unit based on the first device-specific identification number a public key extraction unit for extracting the public key;
When the first public key is extracted, the first public key is transmitted to the first user terminal and, at the same time, an encryption command instructing to encrypt the document file with the first public key is transmitted to the first user terminal Encrypted information transmission unit; and
When encryption of the document file is completed in the first user terminal, an encryption message receiving unit for receiving an encryption completion message indicating that encryption of the document file is completed from the first user terminal
A document security service server that supports encryption of a document file based on terminal information including a. According to claim 1,
In the key pair storage unit,
For each of the n key pairs, preset different integer values of 0 or more and n-1 or less corresponding to each of the n key pairs are additionally stored in correspondence,
The public key extraction unit
When the first device-specific identification number is received from the first user terminal, the first device-specific identification number is converted into a first integer value that is an integer of a decimal number, and the first integer value is divided by n as a divisor By performing a modulo operation, a first operation value is calculated, and after selecting the first key pair corresponding to the first operation value from the key pair storage unit, the first public in the first key pair A document security service server that supports encryption of document files based on the terminal information from which the key is extracted. 3. The method of claim 2,
After receiving the encryption completion message from the first user terminal, as the encrypted document file is executed in the first user terminal, when a decryption request signal for the encrypted document file is received from the first user terminal, a decryption information request unit for requesting transmission of a device-specific identification number for the first user terminal to the first user terminal;
When the first device-specific identification number is received from the first user terminal, the first device-specific identification number is converted into the first integer value that is an integer of a decimal number, and the first integer value is converted to a dividend by n as a divisor The first operation value is calculated by performing a modulo operation to a private key extraction unit for extracting;
When the first private key is extracted, the first private key is transmitted to the first user terminal and, at the same time, a decryption command instructing to decrypt the encrypted document file with the first private key is sent to the first user terminal a decoding information transmission unit to transmit; and
When the decryption of the document file encrypted by the first user terminal is completed, the decryption message receiving unit receives a decryption completion message indicating that the decryption of the encrypted document file is completed from the first user terminal
A document security service server that supports encryption of a document file based on the terminal information further comprising a. 4. The method of claim 3,
When a transmission request signal requesting delivery of the encrypted document file to the second user terminal is received from the first user terminal, the device-specific identification of the encrypted document file and the first user terminal is received by the first user terminal an information request unit for requesting transmission of a number;
When the encrypted document file and the first device-specific identification number are received from the first user terminal, the first device-specific identification number is converted into the first integer value that is an integer of a decimal number, and the first integer value is The first operation value is calculated by performing a modulo operation of dividing n as a divisor as a divisor, and after selecting the first key pair corresponding to the first operation value from the key pair storage unit, the first key pair a decryption unit for extracting the first private key and decrypting the encrypted document file with the first private key;
When a communication connection with the second user terminal is attempted and a communication connection with the second user terminal is established, terminal information for requesting transmission of a device-specific identification number for the second user terminal to the second user terminal request department;
When a second device-specific identification number is received from the second user terminal, a module for converting the second device-specific identification number into a second integer value that is an integer of a decimal number, and dividing the second integer value as a dividend by n An additional key for calculating a second operation value by performing an operation with extraction unit; and
When the second public key is extracted, the document file delivery unit re-encrypts the decrypted document file with the second public key and transmits the re-encrypted document file to the second user terminal
A document security service server that supports encryption of a document file based on the terminal information further comprising a. 4. The method of claim 3,
After receiving the encryption completion message from the first user terminal, when a password setting request signal for enabling password-based auxiliary decryption of the encrypted document file is received from the first user terminal, the first user a first password request unit for requesting transmission of a password to be used for auxiliary decryption of the encrypted document file to a terminal;
a document file request unit for requesting transmission of the encrypted document file to the first user terminal when the first password is received from the first user terminal;
a hash value generator for generating a first hash value by applying the encrypted document file as an input to a preset hash function when the encrypted document file is received from the first user terminal;
a recording unit that records the first hash value, the first device unique identification number, and the first password in correspondence with the first password in a password table;
After the first hash value, the first device unique identification number, and the first password are recorded in the password table, as the encrypted document file is executed in a third user terminal other than the first user terminal, the an event generator generating an event for performing auxiliary decryption of the encrypted document file when a decryption failure message indicating that decryption of the encrypted document file has failed is received from a third user terminal;
a second password request unit for requesting transmission of a password for auxiliary decryption of the encrypted document file and the encrypted document file to the third user terminal when the event occurs;
When the encrypted document file and the second password are received from the third user terminal, the encrypted document file is applied as an input to the hash function to generate the first hash value, and the first hash value is obtained from the password table. Extracts the first password recorded corresponding to the value, checks whether the first password is the same as the second password, and when it is confirmed that the first password is the same as the second password, the second password from the password table an identification number extraction unit for extracting the first device-specific identification number recorded in correspondence to one hash value;
When the first device-specific identification number is extracted from the password table, a module for converting the first device-specific identification number into the first integer value that is an integer of a decimal number, and then dividing the first integer value as a dividend by n By performing an operation, the first operation value is calculated, the first key pair corresponding to the first operation value is selected from the key pair storage unit, and the first private key is extracted from the first key pair. and, when the first private key is extracted, the third user transmits the first private key to the third user terminal and at the same time transmits a decryption command instructing to decrypt the encrypted document file with the first private key. Auxiliary decoding processing unit for transmitting to the terminal; and
When the decryption of the encrypted document file in the third user terminal is completed, the auxiliary decryption completion message receiving unit receives a decryption completion message indicating that the decryption of the encrypted document file is completed from the third user terminal
A document security service server that supports encryption of a document file based on the terminal information further comprising a. maintaining a key pair storage unit in which n different (n is a natural number greater than or equal to 2) key pairs composed of a public key and a private key corresponding to the public key are stored;
When an encryption request signal for the document file generated in the first user terminal is received from a first user terminal among a plurality of user terminals, transmission of a device-specific identification number for the first user terminal to the first user terminal is performed. requesting;
When a first device-specific identification number is received from the first user terminal, the first device constituting a first key pair that is any one of the n key pairs from the key pair storage unit based on the first device-specific identification number extracting the public key;
When the first public key is extracted, the first public key is transmitted to the first user terminal and, at the same time, an encryption command instructing to encrypt the document file with the first public key is transmitted to the first user terminal step; and
When the encryption of the document file is completed in the first user terminal, receiving an encryption completion message indicating that the encryption of the document file is completed from the first user terminal
A method of operating a document security service server that supports encryption of a document file based on terminal information comprising a. 7. The method of claim 6,
In the key pair storage unit,
For each of the n key pairs, preset different integer values of 0 or more and n-1 or less corresponding to each of the n key pairs are additionally stored in correspondence,
The step of extracting the first public key is
When the first device-specific identification number is received from the first user terminal, the first device-specific identification number is converted into a first integer value that is an integer of a decimal number, and the first integer value is divided by n as a divisor By performing a modulo operation, a first operation value is calculated, and after selecting the first key pair corresponding to the first operation value from the key pair storage unit, the first public in the first key pair A method of operating a document security service server that supports encryption of a document file based on terminal information from which a key is extracted. 8. The method of claim 7,
After receiving the encryption completion message from the first user terminal, as the encrypted document file is executed in the first user terminal, when a decryption request signal for the encrypted document file is received from the first user terminal, requesting transmission of a device-specific identification number for the first user terminal to the first user terminal;
When the first device-specific identification number is received from the first user terminal, the first device-specific identification number is converted into the first integer value that is an integer of a decimal number, and the first integer value is converted to a dividend by n as a divisor The first operation value is calculated by performing a modulo operation to extracting;
When the first private key is extracted, the first private key is transmitted to the first user terminal and, at the same time, a decryption command instructing to decrypt the encrypted document file with the first private key is sent to the first user terminal transmitting; and
receiving a decryption completion message indicating that decryption of the encrypted document file is completed from the first user terminal when decryption of the encrypted document file is completed in the first user terminal;
An operating method of a document security service server that supports encryption of a document file based on the terminal information further comprising a. 9. The method of claim 8,
When a transmission request signal requesting delivery of the encrypted document file to the second user terminal is received from the first user terminal, the device-specific identification of the encrypted document file and the first user terminal is received by the first user terminal requesting transmission of the number;
When the encrypted document file and the first device-specific identification number are received from the first user terminal, the first device-specific identification number is converted into the first integer value that is an integer of a decimal number, and the first integer value is The first operation value is calculated by performing a modulo operation of dividing n as a divisor as a divisor, and after selecting the first key pair corresponding to the first operation value from the key pair storage unit, the first key pair extracting the first private key and decrypting the encrypted document file with the first private key;
attempting a communication connection with the second user terminal, and when the communication connection with the second user terminal is established, requesting the second user terminal to transmit a device-specific identification number for the second user terminal;
When a second device-specific identification number is received from the second user terminal, a module for converting the second device-specific identification number into a second integer value that is an integer of a decimal number, and dividing the second integer value as a dividend by n calculating a second calculated value by performing an operation with , selecting a second key pair corresponding to the second calculated value from the key pair storage unit, and then extracting a second public key from the second key pair; and
when the second public key is extracted, re-encrypting the decrypted document file with the second public key and transmitting the re-encrypted document file to the second user terminal
An operating method of a document security service server that supports encryption of a document file based on the terminal information further comprising a. 9. The method of claim 8,
After receiving the encryption completion message from the first user terminal, when a password setting request signal for enabling password-based auxiliary decryption of the encrypted document file is received from the first user terminal, the first user requesting transmission of a password to be used for auxiliary decryption of the encrypted document file to a terminal;
when a first password is received from the first user terminal, requesting transmission of the encrypted document file to the first user terminal;
generating a first hash value by applying the encrypted document file as an input to a preset hash function when the encrypted document file is received from the first user terminal;
recording the first hash value, the first device unique identification number, and the first password in correspondence with the first password in a password table;
After the first hash value, the first device unique identification number, and the first password are recorded in the password table, as the encrypted document file is executed in a third user terminal other than the first user terminal, the generating an event for performing auxiliary decryption of the encrypted document file when a decryption failure message indicating that decryption of the encrypted document file has failed is received from a third user terminal;
when the event occurs, requesting transmission of the encrypted document file and a password for auxiliary decryption of the encrypted document file to the third user terminal;
When the encrypted document file and the second password are received from the third user terminal, the encrypted document file is applied as an input to the hash function to generate the first hash value, and the first hash value is obtained from the password table. Extracts the first password recorded corresponding to the value, checks whether the first password is the same as the second password, and when it is confirmed that the first password is the same as the second password, the second password from the password table extracting the first device unique identification number recorded in correspondence to one hash value;
When the first device-specific identification number is extracted from the password table, a module for converting the first device-specific identification number into the first integer value that is an integer of a decimal number, and then dividing the first integer value as a dividend by n By performing an operation with , the first operation value is calculated, the first key pair corresponding to the first operation value is selected from the key pair storage unit, and the first private key is extracted from the first key pair. and, when the first private key is extracted, the third user transmits the first private key to the third user terminal and at the same time transmits a decryption command instructing to decrypt the encrypted document file with the first private key. transmitting to the terminal; and
When the decryption of the encrypted document file is completed in the third user terminal, receiving a decryption completion message indicating that the decryption of the encrypted document file is completed from the third user terminal
An operating method of a document security service server that supports encryption of a document file based on the terminal information further comprising a. A computer-readable recording medium recording a computer program for executing the method of any one of claims 6 to 10 through combination with a computer. A computer program stored in a storage medium for executing the method of any one of claims 6 to 10 through combination with a computer.

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