JP5468534B2 - Protection level calculation method and protection level calculation system - Google Patents

Description

  Embodiments described herein relate generally to a protection level calculation method and a protection level calculation system.

  In recent years, many leaks of confidential information that should be managed by companies have occurred, and companies that have leaked confidential information are liable for damage from the viewpoint of protecting personal information. In particular, information leakage caused by taking a terminal or storage medium storing personal information out of the office and losing it or being stolen continues to be blamed, and the company that caused the leakage is still liable. There are some cases.

  When a terminal or storage medium storing personal information is lost or stolen, the degree of personal information stored in the terminal or storage medium managed by the employee is low due to low employee awareness or ignorance. One reason is that security awareness when handling terminals and storage media is lowered because they do not know or are not aware of this. Under such circumstances, it is required to appropriately manage the assets of IT assets in a company, and a method for preventing leakage of confidential information has been proposed.

  As an example, this method checks the contents of information (electronic file) in order to know in advance how much danger there is when information is leaked, and the information (electronic file). There are methods for determining the overall protection level. In the method for determining the protection level, first, a personal information dictionary is prepared, whether or not a keyword in the dictionary is included in the information (electronic file), and whether or not an individual can be identified from the hit keyword group is determined. Be evaluated. Thereby, the level of confidentiality is quantified, and the total protection level of information (electronic file) is determined.

  In addition, a method is also known that enables logical circuit operations such as four arithmetic operations while keeping information secret in order to prevent information leakage during information processing. In this method, it is possible to perform a secret calculation for all operations that can be realized in a logic circuit.

  In addition, it is possible to determine whether the information held by the other party is the same as the information held by the other party by using a cryptographic protocol that can secretly calculate the common set between the two parties. Technology is also known. There is also known a system that applies such a technique to detect and determine a spear-type cyber attack in which virus samples in a plurality of companies are compared to attack a specific server. In this system, secure matching is performed by matching secret data and obtaining a common set.

JP 2007-323511 A JP 2009-199068 A

“Started joint demonstration experiment for development of spear-type cyber-attack judgment system-To realize a system for early detection of cyber-attacks limited to specific organizations”, [online], [December 6, 2010] Day search], Internet <http://www2.nict.go.jp/pub/whatsnew/press/h19/080303/080303_1.html>

  Here, the method for determining the protection level is a method of extracting a keyword that can be personal information by text matching between text information of an electronic file and a personal information dictionary. However, there are companies that have established a rule to encrypt an electronic file when storing the important electronic file.

  For this reason, when the file is encrypted, the method for determining the protection level described above does not hit the personal information, and the protection level cannot be determined. In addition, in order to determine the protection level using the above-described method for determining the protection level in a situation where an encrypted file is placed, the encrypted electronic file is decrypted every time matching is performed. Although a method is conceivable, there is a possibility that the security level is lowered by once decrypting the encrypted data when performing matching.

  That is, the above-described conventional technique has a problem that the protection level of the information cannot be determined in a state where the information is concealed.

  Accordingly, the present invention has been made to solve the above-described problems of the prior art, and a protection level calculation method and a protection level capable of determining the protection level of the information in a state where the information is concealed. An object is to provide a calculation system.

In order to solve the above-described problems and achieve the object, a protection level calculation method disclosed in the present application includes a terminal that holds data for calculating a protection level, a first device connected to the terminal, and a first device This is applied to a protection level calculation system having two devices. The protection level calculation method disclosed in the present application includes: a storage step of storing a plurality of character strings used for calculating a data protection level in a predetermined storage unit of an external device connected to the terminal; The data for calculating the protection level is divided into first data and second data, the first data is transmitted to the first device, and the second data is transmitted to the second device. A first calculation instruction step to be transmitted to the external device, and the external device divides one character string selected from a plurality of character strings stored in the predetermined storage unit into a first character string and a second character string And a second operation instruction step of transmitting the first character string to the first device and transmitting the second character string to the second device. Further, the protection level calculation method disclosed in the present application is such that the first device uses the second data and the second data from the first data and the logic circuit that performs text matching with the first character string. Is generated, conversion data that can output the result of text matching between the data and the selected character string is generated, and the generated conversion data is transmitted to the second device. A conversion data generation step; and the second device calculates the calculation result by inputting the second data and the second character string into the conversion data received from the first device, A calculation result calculating step of transmitting the calculated calculation result to the external device. Further, the protection level calculation method disclosed in the present application repeats the processing of the second calculation instruction step until the external device receives all calculation results for all character strings stored in the predetermined storage unit. A third operation instruction step for controlling the conversion data generation step and the operation result calculation step to be executed repeatedly; and the external device controls the entire operation instruction step by controlling the third operation instruction step. A protection level calculating step of calculating a protection level using all the received calculation results when the calculation result is received.

  The protection level calculation system disclosed in the present application includes a terminal that holds data for calculating the protection level, and a first device and a second device connected to the terminal. The protection level calculation system disclosed in the present application includes a predetermined storage unit that stores a plurality of character strings used by an external device connected to the terminal to calculate a protection level of data, and the terminal includes the protection Data for calculating the level is divided into first data and second data, the first data is transmitted to the first device, and the second data is transmitted to the second device. The first operation instruction unit and the external device divide one character string selected from a plurality of character strings stored in the predetermined storage unit into a first character string and a second character string, A second operation command unit that transmits a first character string to the first device and transmits the second character string to the second device. Further, the protection level calculation system disclosed in the present application is configured such that the first device includes the second data and the second data from the first data and a logic circuit that performs text matching with the first character string. Is generated, conversion data that can output the result of text matching between the data and the selected character string is generated, and the generated conversion data is transmitted to the second device. The conversion data generation unit and the second device calculate the calculation result by inputting the second data and the second character string to the conversion data received from the first device, A calculation result calculation unit that transmits the calculated calculation result to the external device. Further, the protection level calculation system disclosed in the present application repeats the processing by the second calculation instruction unit until the external device receives all calculation results for all the character strings stored in the predetermined storage unit. Then, a third calculation command unit that controls the processes of the conversion data generation unit and the calculation result calculation unit to be repeatedly executed, and the external device controls the entire calculation command unit to And a protection level calculation unit that calculates a protection level using all the received calculation results when a calculation result is received.

  According to the protection level calculation method and the protection level calculation system disclosed in the present application, it is possible to determine the protection level of the information while keeping the information secret.

FIG. 1 is a diagram for explaining a configuration example of a protection level calculation system according to the present embodiment. FIG. 2 is a diagram for explaining an example of the keyword storage unit. FIG. 3 is a diagram for explaining the first arithmetic instruction unit. FIG. 4 is a diagram for explaining the second operation instruction unit. FIG. 5 is a diagram for explaining an example of processing of the protection level calculation unit. FIG. 6 is a diagram for explaining an example of processing of the setting unit. FIG. 7 is a sequence diagram for explaining processing until the calculation result of the protection level calculation system according to the present embodiment is acquired. FIG. 8 is a flowchart for explaining the processing after obtaining the calculation result of the protection level calculation system according to the present embodiment. FIG. 9 is a diagram for explaining a modification of the protection level calculation system according to the present embodiment.

  Hereinafter, embodiments of the protection level calculation method and the protection level calculation system disclosed in the present application will be described in detail. Hereinafter, a protection level calculation system that executes the protection level calculation method disclosed in the present application will be described as an example. In addition, this invention is not limited by the following examples.

  A protection level calculation system according to the present embodiment will be described with reference to FIG. FIG. 1 is a diagram for explaining a configuration example of a protection level calculation system according to the present embodiment.

  As illustrated in FIG. 1, the protection level calculation system according to the present embodiment includes a client terminal 10, a first server 20, and a second server 30. Further, the protection level calculation system according to the present embodiment includes an external device 40 as shown in FIG. The client terminal 10, the first server 20, the second server 30, and the external device 40 are connected via a network. In the example shown in FIG. 1, the client terminal 10, the first server 20, the second server 30, and the external device 40 are connected by a LAN (Local Area Network) 100.

  For example, the user a of the client terminal 10 is an employee of the company A, and the client terminal 10 is a personal computer supplied to the user a from the company B, and holds data for calculating the protection level. Each of the first server 20 and the second server 30 is a server installed in the company A for preventing information leakage. In the example shown in FIG. 1, only one client terminal 10 is shown, but actually, the protection level calculation system according to the present embodiment includes a plurality of client terminals 10.

  A data storage unit 11 included in the client terminal 10 illustrated in FIG. 1 stores data held by the client terminal 10. Specifically, the data storage unit 11 stores electronic data created by the user a, electronic data provided to the user a, and the like. For example, the data storage unit 11 stores electronic data of internal materials such as presentation materials, quotations, minutes in company A, minutes of company A and other companies.

  The protection level calculation system according to the present embodiment calculates the protection level of data (information) held by the client terminal 10. Here, in the protection level calculation system according to the present embodiment, each unit shown in FIG. 1 is installed to determine the protection level of the information in a state where the information is concealed. That is, the client terminal 10 includes a first calculation instruction unit 13a as shown in FIG. The external device 40 includes a keyword storage unit 12, a second calculation command unit 13 b, a third calculation command unit 13 c, a protection level calculation unit 14, and a setting unit 15. Here, the first operation instruction unit 13a, the second operation instruction unit 13b, and the third operation instruction unit 13c function as the operation instruction unit 13 that performs an instruction for calculating the protection level by a secret calculation method described later. (See FIG. 1). Note that the external device 40 may be a personal computer, as with the client terminal 10, or a workstation.

  Moreover, the 1st server 20 has the 1st memory | storage part 20a and the conversion data production | generation part 20b, as shown in FIG. The second server 30 includes a second storage unit 30a and a calculation result calculation unit 30b. Hereinafter, each part is demonstrated along the process sequence which the protection level calculation system which concerns on a present Example performs.

  The keyword storage unit 12 included in the external device 40 stores a plurality of character strings (keywords) used for calculating the protection level of data stored in the data storage unit 11. FIG. 2 is a diagram for explaining an example of the keyword storage unit.

  For example, as shown in FIG. 2, the keyword storage unit 12 stores a plurality of “last names: Suzuki, Saito, Sato, Ito,...” As keywords as “Dictionary 1”. Further, as shown in FIG. 2, the keyword storage unit 12 stores a plurality of “names” as keywords as “dictionary 2”. Further, as shown in FIG. 2, the keyword storage unit 12 stores a plurality of “addresses: Chuo-ku, Tokyo,... In the example shown in FIG. 2, all the keywords are expressed in Kanji. For example, the keyword includes not only a character string expressed in Kanji but also a character string expressed in Hiragana, Katakana, and Roman characters. In addition to Japanese, keywords may include English, Chinese, and the like. Although not shown in FIG. 2, the keyword storage unit 12 includes a dictionary of e-mail addresses, a dictionary of words indicating confidentiality levels (for example, confidential information, confidential information, etc.), a phone number dictionary, and a postal code dictionary. Remember.

  Further, as shown in FIG. 2, the keyword storage unit 12 stores “coefficient: 1.0” in association with “dictionary 1” and “dictionary 2” and stores “coefficient: 2.0” in “dictionary 3”. "Is stored in association with each other. The “coefficient” stored in the keyword storage unit 12 is a value used for processing of the protection level calculation unit 14 described in detail later.

  The plurality of keywords stored in the keyword storage unit 12 are character strings used for text matching with data that is a protection level calculation target (hereinafter referred to as target data). The plurality of keywords are stored in the keyword storage unit 12 by an administrator of the protection level calculation system, for example.

  Returning to FIG. 1, the first operation command unit 13 a of the client terminal 10 divides the target data into first data and second data. Then, the first arithmetic instruction unit 13 a transmits the first data obtained by fragmenting the target data to the first server 20. Thus, the first data is stored in the first storage unit 20a. In addition, the first arithmetic instruction unit 13 a transmits second data obtained by fragmenting the target data to the second server 30. Thus, the second data is stored in the second storage unit 30a.

  Specifically, the first arithmetic instruction unit 13a randomly generates (s, t) satisfying the following expression (1) from the data “m” by using a division operator.

  FIG. 3 is a diagram for explaining the first arithmetic instruction unit. For example, the first arithmetic instruction unit 13a sets electronic data newly stored in the data storage unit 11 as “target data: D”. For example, the protection level calculation unit 14 to be described later notifies the first calculation command unit 13a of the data newly stored in the data storage unit 11 as “target data: D”. Then, the first arithmetic instruction unit 13a sets “target data: D” to “m” in the equation (1), and thus corresponds to “t” in the equation (1) as shown in FIG. First data: α ”and“ second data: β ”corresponding to“ s ”in equation (1) are randomly generated.

  Then, as shown in FIG. 3, the first arithmetic instruction unit 13 a stores “first data: α” in the first storage unit 20 a via the LAN 100. In addition, as illustrated in FIG. 3, the first calculation instruction unit 13 a stores “second data: β” in the second storage unit 30 a via the LAN 100.

  Returning to FIG. 1, the second operation instruction unit 13 b included in the external device 40 selects one character string selected from a plurality of character strings stored in the keyword storage unit 12 as the first character string and the second character. Divide into columns. Then, the second arithmetic instruction unit 13 b transmits the first character string to the first server 20. Thereby, the conversion data generation unit 20b receives the first character string. In addition, the second arithmetic instruction unit 13 b transmits the second character string to the second server 30. Thereby, the calculation result calculation unit 30b receives the second character string.

  First, the second calculation instruction unit 13 b selects one keyword “d” from a plurality of keywords stored in the keyword storage unit 12. For example, the second arithmetic instruction unit 13b selects “Suzuki” from the keyword group shown in FIG.

  FIG. 4 is a diagram for explaining the second operation instruction unit. Then, the second operation instruction unit 13b sets “keyword: d” to “m” in the expression (1), thereby, as shown in FIG. 4, the “second” corresponding to “t” in the expression (1). 1 character string: dα ”and“ second character string: dβ ”corresponding to“ s ”in Expression (1) are randomly generated.

  Then, as illustrated in FIG. 4, the second operation command unit 13 b transmits “first character string: dα” obtained by fragmenting “d” to the conversion data generation unit 20 b via the LAN 100. Further, as illustrated in FIG. 4, the second calculation instruction unit 13 b transmits “second character string: dβ” obtained by fragmenting “d” to the calculation result calculation unit 30 b via the LAN 100.

  Returning to FIG. 1, the conversion data generation unit 20b of the first server 20 generates conversion data using the first data (α) and the first character string (dα) and a logic circuit that performs text matching. To do. Here, the conversion data generated by the conversion data generation unit 20b is inputted with the second data (β) and the second character string (dβ), so that the target data (D) and one selected keyword ( This is data that can output the result of the text matching operation with d). Then, the conversion data generation unit 20 b transmits the generated conversion data to the calculation result calculation unit 30 b of the second server 30.

  Then, the calculation result calculation unit 30b calculates the calculation result by inputting the second data and the second character string to the conversion data received from the conversion data generation unit 20b.

  Here, the conversion data generation unit 20b and the calculation result calculation unit 30b generate conversion data using the secret calculation method disclosed in Japanese Patent Laid-Open No. 2009-199068, and calculate the calculation result. Hereinafter, an example of processing executed by the conversion data generation unit 20b will be briefly described using mathematical expressions. In the following formula, the target data (D) and the keyword (d) are described as “m”, and the logic circuit for performing text matching is described as “f”. In the following formula, the first data (α) and the first character string (dα) are described as “t”, and the second data (β) and the second character string (dβ) are expressed as “s”. ".

  First, the conversion data generation unit 20b generates two fixed-length random numbers shown in the following formula (2) for each wire “i” of “f”, and corresponds to “0” and “1”, respectively. Let

Then, the conversion data generation unit 20b generates a random bit “c _i ”. Here, the conversion data generation unit 20b defines “1-c” by the following equation (3).

  Then, the conversion data generation unit 20b associates the value shown in the following expression (4) with the wire “i”.

However, when the wire “i” receives the lower “w” -th bit “m _w ” of the wire “i” as “m”, the converted data generation unit 20 b sets the lower “t” -th bit of “t” to “t _w The value shown in the following formula (5) is made to correspond to the wire “i”.

Then, the conversion data generation unit 20b applies the four labeled data shown in the following equation (6) to the logic gate “g” having “i” and “j” as input wires and “k” as output wires. Are arranged in a random order in units of rows as “T _g ”.

Here, the conversion data generation unit 20b sets the left side of the colon (:) in the expression (6) as “label” and the right side of the colon (:) in the expression (6) as “data”. “F _w (x)” shown in Expression (6) is a function that outputs a fixed-length random number when “x” and “W” are input.

The conversion data generation unit 20b generates “a set of“ T _g ”shown in Expression (6)” as the conversion data. The converted data generating unit 20b transmits the "set a _{T g"} to the calculation result calculation unit 30b.

  The calculation result calculation unit 30b uses “s” to obtain a value represented by the following expression (7).

At this time, the operation result calculation unit 30b executes the conversion data generation unit 20b and the “1-out-of-2 OT protocol” which is a kind of lost communication (OT: Oblivious Transfer) protocol, and is subordinate to “s”. Data having “w” -th bit “s _w ” as input is obtained by the following equation (8).

  In the procedures shown in the equations (7) and (8), the “1-out-of-2 OT protocol” is used. In this protocol, when the first server 20 has the data “d0, d1” and the second server 30 has the bit “b”, the second server 30 can obtain “db”. . However, in this protocol, the first server 20 cannot obtain “b”. In this protocol, the second server 30 cannot obtain the value of the following formula (9).

Then, the calculation result calculation unit 30b obtains Expression (10), which is the output of the final wire of the logic circuit “f”, using “T _g ” and Expression (7). Here, “b = m _w ” is assumed.

The process for obtaining Equation (10) is as follows. That is, for the calculation result calculation unit 30b, “T _g ” corresponding to the logic gate “g” of the input wires “i” and “j” and the output wire “k”, and the following equation (11): And given a value.

In such a case, the calculation result calculation unit 30b first extracts Expression (13), which is data having a label represented by Expression (12) below, from “T _g ”.

  And the calculation result calculation part 30b calculates the value shown to the following formula | equation (14).

  Thereby, the calculation result calculation unit 30b obtains the following expression (15) which is data corresponding to the output wire “k”.

  The calculation result calculation unit 30b performs the same process for the other gates, thereby obtaining Expression (10) that is the output of the final-stage wire.

The calculation result calculation unit 30b calculates the calculation result “b ′” of the logic circuit “f” that performs text matching by setting “c _k = 0” in Equation (10). Specifically, the calculation result calculation unit 30b calculates the frequency at which the keyword (d) appears in the target data (D).

  Then, the calculation result calculation unit 30 b transmits the calculated calculation result to the external device 40. Specifically, the calculation result calculation unit 30b transmits the calculated calculation result to the third calculation command unit 13c illustrated in FIG. 1, and the third calculation command unit 13c calculates the received calculation result as a protection level. Notification to the unit 14.

  The third operation instruction unit 13c repeats the processing by the second operation instruction unit 13b until it receives all the operation results for all the character strings (keywords) stored in the keyword storage unit 12, thereby converting the data generation unit Control is performed so that the processing of 20b and the calculation result calculation unit 30b is repeatedly executed.

  Then, when all the calculation results are received under the control of the third calculation command unit 13c, the protection level calculation unit 14 calculates the protection level of the target data using the received all calculation results.

  FIG. 5 is a diagram for explaining an example of processing of the protection level calculation unit. For example, as shown in FIG. 5A, the protection level calculation unit 14 has a frequency of “100” in which all keywords in “Dictionary 1 (surname)” appear in “target data: D”. In this case, a multiplication value “100” obtained by multiplying the coefficient “1.0” of “Dictionary 1 (surname)” by “100” is calculated. Further, as shown in FIG. 5A, the protection level calculation unit 14 has a frequency of “100” in which all keywords in “dictionary 2 (name)” appear in “target data: D”. In this case, a multiplication value “100” obtained by multiplying the coefficient “1.0” of “Dictionary 2 (name)” by “100” is calculated. Further, as shown in FIG. 5A, the protection level calculation unit 14 has a frequency of “200” in which all keywords in “dictionary 3 (address)” appear in “target data: D”. In this case, a multiplication value “400” obtained by multiplying the coefficient “2.0” of “Dictionary 3 (address)” by “200” is calculated.

  The protection level calculation unit 14 performs such processing in all dictionaries. Then, the protection level calculation unit 14 calculates the total value “S (D)” of the multiplication values as shown in FIG.

  And the protection level calculation part 14 calculates a protection level according to "S (D)", as shown to (B) of FIG. For example, the protection level calculation unit 14 calculates the protection level using the first threshold value and the second threshold value. For example, the protection level calculation unit 14 calculates the protection level “low” when “S (D)” is equal to or less than the first threshold. Further, the protection level calculation unit 14 calculates the protection level “medium” when “S (D)” is larger than the first threshold and equal to or less than the second threshold. Further, the protection level calculation unit 14 calculates the protection level “high” when “S (D)” is larger than the second threshold.

  The protection level calculation unit 14 may calculate the protection level using a value obtained by multiplying “S (D)” by “the total value of frequencies” as a value obtained by normalizing all the calculation results. The policy used when the protection level calculation unit 14 calculates the protection level can be arbitrarily set by the administrator of the protection level calculation system. As an example of the policy, there is a policy of setting the protection level to “high” when the frequency of “dictionary 1” is “150” or more and the frequency of “dictionary 3” is “200” or more.

  In the above description, the case where the protection level is calculated in three stages has been described. However, the protection level calculated in the present embodiment may be set in an arbitrary stage. For example, the protection level calculated in the present embodiment may be 10 levels.

  Returning to FIG. 1, the setting unit 15 included in the external device 40 performs external processing on the target data “D” from which the protection level is calculated according to the protection level calculated by the protection level calculation unit 14. Set restrictions on taking out. That is, the setting unit 15 sets restrictions on the external take-out of the target data “D” for the client terminal 10.

  FIG. 6 is a diagram for explaining an example of processing of the setting unit. For example, as illustrated in FIG. 6, the setting unit 15 sets a restriction of “external take-out prohibition” for the target data “D” for which “protection level: high” is calculated. Thus, even if the user a tries to copy the target data “D” by connecting a USB (Universal Serial Bus) memory to the client terminal 10, for example, the copy cannot be performed due to the restrictions set by the setting unit 15. For example, even if the user a tries to transmit the target data “D” after attaching the target data “D” to the mail, the user a cannot be attached due to the restriction set by the setting unit 15.

  Further, as illustrated in FIG. 6, the setting unit 15 sets a restriction of “encrypted and can be taken outside” for the target data “D” for which “protection level: medium” is calculated. Thereby, the user a can copy to the USB memory or send it by e-mail only when the target data “D” is encrypted.

  In addition, as illustrated in FIG. 6, the setting unit 15 sets a restriction of “external take-out” for the target data “D” for which “protection level: low” is calculated.

  Next, a processing flow of the protection level calculation system according to the present embodiment will be described with reference to FIGS. FIG. 7 is a sequence diagram for explaining processing until the calculation result of the protection level calculation system according to the present embodiment is acquired. FIG. 8 is a flowchart for explaining the processing after obtaining the calculation result of the protection level calculation system according to the present embodiment.

  As illustrated in FIG. 7, in the protection level calculation system according to the present embodiment, when new data “target data (D)” is stored in the data storage unit 11, the protection level calculation unit 14 selects the target data (D ) Is requested to the operation instruction unit 13 (first operation instruction unit 13a) (step S101). Then, the operation instruction unit 13 (first operation instruction unit 13a) fragments the target data (D) into α and β (step S102).

  Then, the operation instruction unit 13 (first operation instruction unit 13a) transmits α to the first storage unit 20a (step S103), and the first storage unit 20a stores α (step S104). The operation instruction unit 13 (first operation instruction unit 13a) transmits β to the second storage unit 30a (step S105), and the second storage unit 30a stores β (step S106).

  Thereafter, the operation instruction unit 13 (second operation instruction unit 13b) fragments the keyword (d) selected from the keyword storage unit 12 into dα and dβ (step S107).

  Then, the operation instruction unit 13 (second operation instruction unit 13b) transmits dα to the conversion data generation unit 20b (step S108), and the conversion data generation unit 20b receives dα (step S109). In addition, the operation instruction unit 13 (second operation instruction unit 13b) transmits dβ to the operation result calculation unit 30b (step S110), and the operation result calculation unit 30b receives dβ (step S111).

  Then, the conversion data generation unit 20b extracts α from the first storage unit 20a, and generates conversion data from a logic circuit that performs α, dα, and text matching (step S112). Subsequently, the conversion data generation unit 20b transmits the conversion data to the calculation result calculation unit 30b (step S113), and the calculation result calculation unit 30b receives the conversion data (step S114).

  Then, the calculation result calculation unit 30b extracts β from the second storage unit 30a, inputs β and dβ into the conversion data, calculates the calculation result (step S115), and calculates the calculation result to the calculation command unit 13 (first step). 3 (operation instruction unit 13c) (step S116).

  Then, the calculation command unit 13 (third calculation command unit 13c) receives the calculation result, notifies the received calculation result to the protection level calculation unit 14 (step S117), and the protection level calculation unit 14 Is received (step S118).

  Then, the calculation command unit 13 (third calculation command unit 13c) performs control so that the processes in steps S107 to S118 are repeated until all calculation results are received (step S119).

  Thereby, matching processing of all keywords is performed, and the protection level calculation unit 14 receives all calculation results. In the above description, the case where the keyword selection process is performed by the second arithmetic instruction unit 13b has been described. However, the keyword selection process may be performed by the protection level calculation unit 14. In such a case, the protection level calculation unit 14 notifies the selected keyword to the second calculation command unit 13b, and the second calculation command unit 13b performs a division (fragmentation) process and a transmission process of the notified keyword. .

  Then, as shown in FIG. 8, the protection level calculation unit 14 determines whether or not all the calculation results have been received under the control of the calculation command unit 13 (third calculation command unit 13c) (step S201). Here, when all the calculation results have not been received (No at Step S201), the protection level calculation unit 14 stands by until all the calculation results are received.

  On the other hand, when all the calculation results are received (Yes at Step S201), the protection level calculation unit 14 calculates the protection level (Step S202).

  Then, the setting unit 15 sets restrictions on the target data “D” according to the protection level (step S203), and ends the process.

  In the above description, the protection level calculation process is executed at the timing when data is newly stored in the client terminal. However, the present embodiment is not limited to this. For example, in this embodiment, even when the protection level calculation process is executed at a predetermined interval (for example, one month) and the target data is a data group newly stored at the predetermined interval. good. In this embodiment, when the keyword group in the keyword storage unit 12 is updated, the protection level calculation process may be performed on all data stored in the data storage unit 11.

  In the above description, the conversion data is generated by the first server 20 and the calculation result is calculated by the second server 30. However, the present embodiment is not limited to this. . For example, the present embodiment may be a case where the conversion data is generated by the second server 30 and the calculation result is calculated by the first server 20. Further, in this embodiment, both the first server 20 and the second server 30 can execute the conversion data generation process and the calculation result calculation process, and the conversion data generation process for each target data or for each keyword. And the case where the server which performs a calculation result calculation process may be changed.

  As described above, in the present embodiment, the keyword storage unit 12 stores a plurality of character strings used for calculating the protection level of data. The first operation command unit 13a divides data for calculating the protection level into first data and second data, transmits the first data to the first server 20, and sends the second data to the first data. Transmit to the second server 30. The second arithmetic instruction unit 13b divides one character string selected from the plurality of character strings stored in the keyword storage unit 12 into a first character string and a second character string, and the first character string is The data is transmitted to the first server 20, and the second character string is transmitted to the second server 30.

  The conversion data generation unit 20b is selected as data by inputting the second data and the second character string from the first data and the logic circuit that performs text matching with the first character string. Conversion data that can output the result of calculation of text matching with one character string is generated, and the generated conversion data is transmitted to the second server 30. And the calculation result calculation part 30b calculates a calculation result by inputting 2nd data and a 2nd character string into the conversion data received from the 1st server 20, and calculates the calculated calculation result to a client terminal 10 to send.

  The third operation instruction unit 13c repeats the processing by the second operation instruction unit 13b until it receives all the operation results for all the character strings stored in the keyword storage unit 12, thereby allowing the conversion data generation unit 20b and the operation to be performed. It controls so that the process of the result calculation part 30b is repeatedly performed. When the protection level calculation unit 14 receives all the calculation results under the control of the third calculation command unit 13c, the protection level calculation unit 14 calculates the protection level using the received all calculation results.

  That is, in this embodiment, the keyword group storage, keyword selection, keyword division, and iterative control until all calculation results are calculated, and the protection level calculation process are integrated and executed in the external device 40. In this embodiment, the data is fragmented and stored in two servers. For example, even if an employee takes out a storage medium storing data fragments, the original data cannot be decrypted. It does not lead to information leakage. For example, by managing different storage media storing two pieces by different managers, it is possible to increase resistance to manager fraud.

  In this embodiment, the keyword is also fragmented, and a secret calculation is performed between the first server 20 and the second server 30 to calculate a calculation result. That is, in the present embodiment, the first server 20 can generate the conversion data and the second server 30 can calculate the calculation result without decrypting the target data and keywords. In other words, in the present embodiment, how much important file the storage medium (data storage unit 11) that stores data holds and what level of protection is required are stored in the data. Since the calculation is performed in the encrypted state, the security level is not lowered.

  Therefore, in this embodiment, it is possible to determine the protection level of the information while keeping the information secret.

  The first server 20 and the second server 30 may discard the stored first data and second data when all the calculation results are calculated. Such processing makes it possible to enhance information leakage prevention.

  Further, in the present embodiment, the setting unit 15 sets restrictions on external take-out for the data from which the protection level is calculated according to the protection level calculated by the protection level calculation unit 14. Therefore, in this embodiment, appropriate restrictions can be imposed according to the protection level of the information calculated in a state where the information is concealed, and information leakage prevention can be further strengthened.

  Note that the case where the setting unit 15 is installed in the external device 40 has been described above. However, this embodiment may be a case where the setting unit 15 is installed in the client terminal 10 as shown in FIG. FIG. 9 is a diagram for explaining a modification of the protection level calculation system according to the present embodiment. In such a case, the setting unit 15 receives the protection level of the target data from the protection level calculation unit 15 of the external device 40, and sets restrictions based on the received protection level.

  In addition, among the processes described in this embodiment, all or part of the processes described as being performed automatically can be performed manually, or the processes described as being performed manually can be performed. All or a part can be automatically performed by a known method. In addition, the processing procedure, control procedure, specific name, and information including various data and parameters shown in the above document and drawings can be arbitrarily changed unless otherwise specified.

  Further, each component of each illustrated apparatus is functionally conceptual, and does not necessarily need to be physically configured as illustrated. In other words, the specific form of distribution / integration of each device is not limited to that shown in the figure, and all or a part thereof may be functionally or physically distributed or arbitrarily distributed in arbitrary units according to various loads or usage conditions. Can be integrated and configured. Specifically, the present embodiment may be a case where the function of the external device 40 is integrated into the first server 20 or a case where it is integrated into the second server 30. Further, all or any part of each processing function performed in each device may be realized by a CPU and a program analyzed and executed by the CPU, or may be realized as hardware by wired logic.

  The protection level calculation method described in the present embodiment can be realized by executing a program prepared in advance on a computer such as a personal computer or a workstation. This program can be distributed via a network such as the Internet. The program can also be executed by being recorded on a computer-readable recording medium such as a hard disk, a flexible disk (FD), a CD-ROM, an MO, and a DVD, and being read from the recording medium by the computer.

  As described above, the protection level calculation method and the protection level calculation system according to the present invention are useful when calculating the protection level of information, and in particular, determine the protection level of the information in a state where the information is concealed. Suitable for that.

DESCRIPTION OF SYMBOLS 10 Client terminal 11 Data storage part 12 Keyword storage part 13 Operation instruction part 13a 1st operation instruction part 13b 2nd operation instruction part 13c 3rd operation instruction part 14 Protection level calculation part 15 Setting part 20 1st server 20a First storage unit 20b Conversion data generation unit 30 Second server 30a Second storage unit 30b Calculation result calculation unit 40 External device

Claims (3)

A protection level calculation method applied to a protection level calculation system having a terminal that holds data for calculating a protection level, and a first device and a second device connected to the terminal,
A storage step of storing a plurality of character strings used for calculating a data protection level in a predetermined storage unit of an external device connected to the terminal;
The terminal divides data for calculating the protection level into first data and second data, transmits the first data to the first device, and transmits the second data to the first data A first operation instruction step to transmit to the two devices;
The external device divides one character string selected from a plurality of character strings stored in the predetermined storage unit into a first character string and a second character string, and the first character string is converted into the first character string. A second operation instruction step for transmitting to the first device and transmitting the second character string to the second device;
The first device inputs the second data and the second character string from a logic circuit that performs text matching with the first data and the first character string, and the data and A conversion data generation step of generating conversion data capable of outputting a result of a text matching operation with the selected one character string, and transmitting the generated conversion data to the second device;
The second device calculates the calculation result by inputting the second data and the second character string to the conversion data received from the first device, and the calculated calculation result is A calculation result calculation step to be transmitted to the external device;
The conversion data generation step and the calculation result calculation are performed by repeating the processing of the second calculation command step until the external device receives all calculation results for all the character strings stored in the predetermined storage unit. A third operation instruction step for controlling the processing of the step to be repeatedly executed;
A protection level calculating step of calculating a protection level using the received all calculation results when the external device receives the all calculation results under the control of the third calculation command step;
The protection level calculation method characterized by including. A setting step in which the terminal or the external device sets a restriction on external takeout for the data from which the protection level is calculated according to the protection level calculated in the protection level calculation step. The protection level calculation method according to claim 1, further comprising: A protection level calculation system having a terminal that holds data for calculating a protection level, and a first device and a second device connected to the terminal,
A predetermined storage unit that stores a plurality of character strings used by an external device connected to the terminal to calculate a protection level of data;
The terminal divides data for calculating the protection level into first data and second data, transmits the first data to the first device, and transmits the second data to the first data A first operation command unit to be transmitted to the second device;
The external device divides one character string selected from a plurality of character strings stored in the predetermined storage unit into a first character string and a second character string, and the first character string is converted into the first character string. A second operation command unit that transmits to the first device and transmits the second character string to the second device;
The first device inputs the second data and the second character string from a logic circuit that performs text matching with the first data and the first character string, and the data and A conversion data generation unit that generates conversion data that can output a result of a text matching operation with the selected one character string, and transmits the generated conversion data to the second device;
The second device calculates the calculation result by inputting the second data and the second character string to the conversion data received from the first device, and the calculated calculation result is A calculation result calculation unit to be transmitted to the external device;
Until the external device receives all the calculation results for all the character strings stored in the predetermined storage unit, the conversion data generation unit and the calculation result calculation are performed by repeating the processing by the second calculation command unit. A third operation instruction unit for controlling the processing of the unit to be repeatedly executed,
A protection level calculation unit that calculates a protection level using the received all calculation results when the external device receives the all calculation results under the control of the third calculation command unit;
A protection level calculation system characterized by comprising:

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