JP5731361B2 - Character string conversion method and character string conversion program - Google Patents

Description

  The present invention relates to a character string conversion technique for protecting personal information included in an electronic document.

  As the importance of protecting personal information increases, there is an increasing expectation for a technology that masks the personal information portion of an electronic document containing personal information such as first and last names and addresses so that it cannot be read. As an existing technique for masking a personal information part included in an electronic document, a technique for performing character string conversion or the like is known (Patent Document 1, etc.).

JP 2007-102540 A

  However, in the existing technology, if the input data includes a character string that matches the character string of the personal information to be masked, the masking is performed, and there is a problem that extra masking is performed.

  When many erroneous masking portions occur, a problem arises in terms of personal information protection, such as the possibility of guessing the original personal information character string from the masked character string increases.

  In particular, when Web page browsing history data including HTML tags is handled as input data, not only the text of the Web page but also the values of HTML elements and attribute information match the character strings included in the personal information dictionary. The corresponding part may be detected as a character string of a mask target candidate. For example, if the personal information dictionary contains character strings such as “Taro Tanaka” or “0123”, “value =“ Taro Tanaka ””, “width =“ 10123 ””, etc. are described as attribute information in the HTML tag. If it is, the corresponding portions of “Taro Tanaka” and “0123” are detected as character strings of candidate masks. At this time, since the character string “0123” included in “width =“ 10123 ”is not personal information, it is a portion that should not be masked.

  As described above, when Web page browsing history data including an HTML tag or the like is used as input data, there is a high possibility that many erroneous mask locations will occur, and the risk of leakage of personal information cannot be reduced.

  In view of the above circumstances, an object of the present invention is to mask personal information included in electronic information without omission without performing unnecessary mask processing.

  Therefore, the present invention reduces the risk of information leakage by selecting character strings to be converted in consideration of the structure of the structured language of the electronic document.

As an aspect of the character string conversion method of the present invention, items of personal information are expressed by a large item and a small item that refines the large item, and personal information character string data to be protected is represented for each small item of personal information. A character string conversion method in which a character string conversion device having a stored personal information dictionary converts personal information included in an electronic document into another character string, and the individual of small items included in the personal information dictionary from the electronic document A procedure for detecting a character string of information as a candidate character string for character string conversion, and when the detected candidate character string is not included in the contents of the tag element of the electronic document , the large items are the same and the small items are different. From the set of candidate character string combinations, a procedure for determining a character string combination having a minimum number of characters between candidate character strings as a target for character string conversion, and a character string determined as the target for character string conversion Place the combination in another string And a procedure to change.

As another aspect of the character string conversion method of the present invention, personal information items are represented by a large item and a small item obtained by refining the large item, and personal information character string data to be protected is represented by a small item of personal information. A character string conversion method for converting personal information included in an electronic document into another character string by a character string conversion device having a personal information dictionary stored for each sub-item included in the personal information dictionary from the electronic document a step of detecting a character string of the personal information as a candidate character string of the character string conversion, if the detected candidate character string is not included in the contents of the tag elements of the electronic document, the small item is a large item same From the set of candidate character string combinations with different character strings, the character string length of the candidate character string combination is shorter than the average character string length in the set, and the selected combination is the target of character string conversion. Judgment procedure , And a procedure to replace the combination of target determined string of the character string converted into another character string.

As another aspect of the character string conversion method of the present invention, personal information items are represented by a large item and a small item that is a refinement of the large item, and the personal information character string data to be protected is represented by a small item of personal information. A character string conversion method for converting personal information included in an electronic document into another character string by a character string conversion device having a personal information dictionary stored for each sub-item included in the personal information dictionary from the electronic document a step of detecting a character string of the personal information as a candidate character string of the character string conversion, if the detected candidate character string is not included in the contents of the tag elements of the electronic document, the small item is a large item same A procedure for determining a combination of character strings having the highest co-occurrence frequency in the electronic document as a character string conversion target from a set of combinations of candidate character strings having different character strings , and a character string determined as the character string conversion target Combination of other statements And a procedure to replace the column.

  Note that the present invention may be a character string conversion program for causing a computer to execute each procedure of the character string conversion method.

  According to the above invention, the personal information included in the electronic information can be masked without omission without performing unnecessary masking.

The block diagram which showed the structure of the character string converter which concerns on embodiment of this invention. The flowchart of the character string conversion process which concerns on embodiment of this invention. An example (a) of personal information concerning an embodiment of the present invention, an example (b) of a personal information dictionary. The flowchart of the mask determination process which concerns on embodiment of this invention. Explanatory drawing of the mask determination which concerns on embodiment of this invention. An example of the personal information periphery description pattern dictionary which concerns on embodiment of this invention. 1 is a block diagram showing a configuration of a network system according to an embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to these embodiments.

[Embodiment 1]
(Overview)
The character string conversion apparatus 1 according to the first embodiment of the invention shown in FIG. 1 is a method of uniformly masking by selecting a portion to be masked in consideration of the structure of the structured language of the electronic document to be masked. Compared to reducing the risk of information leakage. Specifically, a character string of personal information included in the personal information dictionary 30 is detected as a candidate character string for character string conversion from the electronic document to be masked. If the detected candidate character string is not included in the contents of the tag element of the electronic document, a combination of character strings extracted based on a predetermined standard from the set of candidate character string combinations is determined as a character string conversion target. On the other hand, when the detected candidate character string is included in the contents of the tag element of the electronic document, a combination of candidate character strings that matches the personal information included in the personal information dictionary 30 is a target for character string conversion. judge. As described above, a combination of character strings determined to be character string conversion targets is replaced with another character string.

(Device configuration)
As shown in FIG. 1, the character string conversion apparatus 1 includes at least an input data reading unit 20, a personal information dictionary 30, a personal information detection unit 40, a mask target determination unit 50, a mask replacement unit 60, and a mask character string storage unit 80. Prepare. Each function unit 20 to 80 of the character string conversion device 1 is realized by hardware resources of a server (computer). That is, the character string conversion device 1 includes at least hardware resources related to a computer such as a computing device (CPU), a storage device (memory, a hard disk device, etc.), and a communication interface. These hardware resources cooperate with software resources (OS, applications, etc.) to implement the functional units 20-80.

  The input data reading unit 20 reads input data 10 (electronic document) including personal information and stores it as internal data in the memory. As the input data, an electronic document that may contain a personal information character string is used as input data, and an HTML or XML format electronic file is exemplified.

  The personal information dictionary 30 stores personal information character string data to be protected for each item of personal information. For example, the personal information dictionary 30 stores a personal information character string for each item of personal information of a client who owns the character string conversion device 1.

  As illustrated in FIG. 3A, the personal information dictionary 30 can identify an individual such as a name, a telephone number, a mobile phone number, a credit card number, a postal code, an e-mail address, and an address as personal information. Stores information. When personal information of a plurality of individuals is stored, as illustrated in FIG. 3B, the personal information is recorded in association with the names of the individuals. Such personal information is often composed of a plurality of items. For example, if the telephone number is “046-123-4567”, it is composed of a combination of three numeric character strings “046”, “123”, “4567”. Can be treated as being. The personal information dictionary 30 is registered as dictionary information for each item character string constituting the personal information, and may be managed by a database system. Note that the handle name used on the Web page may be targeted as information that can indirectly identify an individual.

  The personal information detection unit 40 detects a character string of personal information included in the personal information dictionary 30 from the input data 10 as a character string conversion candidate character string. Specifically, using the personal information data stored in the personal information dictionary 30 as a key, the input data 10 is searched for a character string corresponding to the personal information, and the corresponding character string is converted into a character string conversion candidate character. A column. For example, in the personal information dictionary 30 shown in FIG. 3B, when the name is stored as a combination of items divided as “last name” and “first name”, the items of “last name” and “first name” are displayed. A search is performed on the entire input data 10 as a key, and the detected character string is set as a candidate character string for character string conversion.

  The mask target determination unit 50 determines whether the candidate character string detected by the personal information detection unit 40 is a character string conversion target. That is, since the detection is performed for each item of the personal information character string registered in the personal information dictionary 30, all character strings that match the items of the personal information character string are detected as character string conversion candidate character strings.

  For example, when the telephone number “046-123-4567” is decomposed into items as “046”, “123”, “4567” and registered in the personal information dictionary 30, “046” included in the input data 10, Character strings “123” and “4567” are candidates for character string conversion. At this time, if there are places in the input data 10 that include character strings such as “ID: 046”, “width =“ 123 ””, and “population 4567”, the characters that are not originally personal information are also written. It will be detected as a candidate for column conversion.

  Therefore, the mask target determination unit 50 detects the item character string that constitutes the original personal information by analyzing the character string included between the candidate characters detected by the personal information detection unit 40 in the input data 10. To do.

  Specifically, when the candidate character string detected by the personal information detection unit 40 is not included in the content of the tag element of the input data 10, the character string extracted on the basis of a predetermined standard from the set of candidate character string combinations. The combination is determined as a character string conversion target. For example, a combination of character strings having the minimum number of characters between candidate character strings is determined as a character string conversion target from the set of candidate character string combinations. Alternatively, a combination of character strings shorter than the average character string length is selected from the set of candidate character string combinations, and the selected combination is determined as a character string conversion target. Alternatively, a combination of character strings selected based on a statistical index from the set of candidate character string combinations is determined as a character string conversion target. Examples of the statistical index include co-occurrence frequency.

  On the other hand, when the candidate character string detected by the personal information detection unit 40 is included in the contents of the tag element of the input data 10, a combination of candidate character strings that match the personal information included in the personal information dictionary 30 is represented by the character string. It is determined that it is a conversion target.

  The mask replacement unit 60 replaces a combination of character strings determined as a character string conversion target by the mask target determination unit 50 with another character string. Other character strings are stored in advance in the mask character string storage unit 80.

(Description of processing procedure)
The procedure S1 to S4 of the character string conversion process executed by the character string conversion device 1 will be described with reference to FIG.

  S1: When the input data reading unit 20 receives the input data 10 (for example, Web page browsing history data including personal information), the input data is read and stored as internal data in the memory.

  S2: The personal information detection unit 40 detects a character string of personal information included in the personal information dictionary 30 as a candidate character string for character string conversion from the input data 10 stored in step S1.

  S3: The mask target determination unit 50 determines whether the candidate character string detected in step S2 is to be subjected to character string conversion.

  Specific steps S301 to S308 of step S3 will be described with reference to FIGS. Here, a case where the input data 10 is an HTML document and “phone number” is detected as personal information from this document will be described.

  S301: Read the candidate character string detected in step S2 from the HTML document as the input data 10. In the example of FIG. 5, for example, when the item character strings “046”, “123”, and “4567” constituting the telephone number “046-123-4567” detected in step S2 are p1, p2, and p3, respectively, Is read as a candidate character string for character string conversion. For example, if a character string conversion candidate detected as p1 is defined as maskTargetP1, the description location of p1 in the HTML document is defined as maskTargetP1 (1), maskTargetP1 (2),. Read.

  S302: The candidate character string read in step S301 may include those included in the content of the tag element of the HTML document (for example, a range surrounded by a start tag and an end tag). Therefore, it is determined whether or not the candidate character string read in step S301 is included in the contents of the tag element of the HTML document. In the example of FIG. 5, it is determined whether or not each maskTargetPn (n) is included in the contents of the range surrounded by the start tag and end tag of the HTML document.

  S303: If it is determined in step S302 that the candidate character string is not included in the content of the tag element of the HTML document (No), the candidate character string includes a plurality of items such as “phone number” and “card number”, for example. It is determined whether or not the item character string of personal information is a character string. In the example of FIG. 5, it is determined whether the candidate character strings “046”, “123”, and “4567” are one of the item characters constituting the personal information stored in the personal information dictionary 30.

  S304: If it is determined in step 303 that the item character string of personal information is a plurality of item character strings (Yes), the item character string of the corresponding personal information not included in the content of the tag element of the HTML document Select all combinations. In the case of FIG. 5, a combination of mask target conversion candidates maskTargetP1 (n), maskTargetP2 (n), and maskTargetP3 (n) that are not included in the contents enclosed by the start tag and end tag of the HTML document is selected.

  S305: Read character string data between item character strings for each combination of item character strings selected in step S304. Among the character strings between the item character strings, the number of characters is counted for character strings that are not included in the content of the HTML document tag element, that is, character strings outside the range enclosed by the start tag and end tag of the HTML document. To do. From the count result, the combination of item character strings having the smallest number of characters is selected from among the combinations of all item character strings. Alternatively, a combination of character strings that is shorter than the average character string length is selected as a mask target candidate from a set of combinations of all item character strings.

  In the example of FIG. 5, the character string between the candidate maskTargetP1 (n) and the candidate maskTargetP2 (n) and the character string between the candidate maskTargetP2 (n) and the candidate maskTargetP3 (n) are read and stored as internal data in the memory. To do. Of these combinations of character strings, if a large number of character strings are included between the candidates, it is considered that the combination is not suitable as a candidate combination for character string conversion. Is selected.

  In step S305, instead of the above selection method considering the number of characters and the character string length, a combination of character strings selected from a set of all item character string combinations based on a statistical index is selected as a mask target candidate. May be. Examples of the combination of character strings selected based on the statistical index include a combination of character strings having the highest co-occurrence frequency in the input data 10.

  S306: The character string selected in step S305 is set as a character string conversion target. On the other hand, if it is determined in step S303 that the candidate character string is not personal information composed of a plurality of items such as “password” and “handle name” (No), the candidate character string is set as a character string conversion target. To do.

  S307: If it is determined in step S302 that the candidate character string is included in the content of the tag element of the HTML document (Yes), the candidate character string may contain personal information (element or attribute) ). If it is determined that the personal information may be included (Yes), the candidate character string to be masked is set as a character string conversion target. In the case of FIG. 5, if the character string indicates the value of the parameter input in the content of the tag element such as “value =“... ”, It is determined that this character string may contain personal information. The character string determined to have the possibility of including personal information is subjected to character string conversion in step S306.

  S308: If it is determined in step S307 that the candidate character string is not the content of a tag element that may contain personal information (No), the candidate character string is determined not to be masked. In the case of FIG. 5, when the character string is shown as the value of the element / attribute of the tag that defines the document structure, such as “width =“... ”, This character string has no possibility of including personal information (No). Therefore, it is excluded from character string conversion.

  S4: The mask replacement unit 60 replaces the character string determined as the character string conversion target in step S3 described above with another character string extracted from the mask character string storage unit 80. As a result, the personal information included in the input data 10 cannot be specified. The input data 10 with the personal information masked in this way is output as output data 70.

  The other character string may be replaced with a character string defined in advance. For example, it may be replaced with a symbol such as “*”. It may be a character string that cannot be read by a third party, and may be a character string such as “* 6: AB1B *” using a character string length to be masked and a hash value of the character string, and the generation method of the mask character string is not limited. Shall. Electronic document data obtained by replacing the mask target character string with a mask character string is output as output data 70.

(Effect of this embodiment)
Therefore, according to the character string converter 1, the personal information included in the electronic information can be masked without omission without performing unnecessary masking.

  That is, when appropriately masking an electronic document containing personal information, conventionally, the attribute information character string in the HTML tag other than the personal information character string was also erroneously masked. Only information strings can be masked appropriately. Accordingly, it is possible to reduce the possibility that the character string before the mask processing is estimated due to the presence of the erroneously masked character string, and it is possible to perform the personal information mask processing that is safer than before.

  In particular, when extracting a character string to be subjected to character string conversion, the character string conversion device 1 uses a combination of character strings having a minimum number of characters between candidate character strings from a set of character string conversion candidate character string combinations. Is selected as the target of character string conversion. Character strings to be masked can be efficiently extracted by selecting character strings depending on the number of characters between candidate character strings.

  Alternatively, a character string combination shorter than the average character string length is selected from the set of candidate character string combinations, and the selected combination is selected as a character string conversion target. The character string to be masked can be efficiently extracted by selecting the character string depending on the length of the combined character string.

  Alternatively, a combination of character strings selected based on a statistical index (co-occurrence frequency or the like) from a set of candidate character string combinations is selected as a character string conversion target. By such statistical processing, a character string to be masked can be extracted efficiently.

[Embodiment 2]
Depending on the type of personal information, a symbol may be interposed between item character strings constituting the personal information. For example, when personal information is a telephone number, credit card, or postal code, a symbol such as “-” (hyphen) is often interposed. When the personal information is a zip code, the symbol “〒” is often written in front of the first item character string, but it is unlikely that the symbol “〒” is interposed between the item character strings. In addition, in the case of an email address, there is a high possibility that “@” is included between the item character strings constituting this, but the contents of the tag element of the electronic document (for example, the start tag and end tag of an HTML document or XML document) There is a low possibility that other character strings not included in the contents of the enclosed range are interposed between the item character strings.

  For other types of personal information, there are symbols and character strings that are likely to intervene before the first item character string and between item character strings, and are unlikely to be included between item character strings. A column exists.

  Therefore, the mask target determination unit 50 according to the second embodiment further improves the determination efficiency of the character string conversion candidate by referring to the personal information notation pattern dictionary 90 that stores the notation pattern information of the personal information.

  The personal information notation pattern dictionary 90 stores the contents of personal information and notation pattern information for each type of personal information as shown in FIG. The column of the notation pattern information stores a symbol, character, or character string that is interposed between the first character character string of the personal information and the item character string that constitutes the personal information. In the dictionary 90 illustrated in FIG. 6, “name”, “phone number”, “mobile phone number”, “credit card number”, “postal code”, “mail address”, and “address” are recorded in the column of the type of personal information. .

  The mask target determination unit 50 refers to the personal information notation pattern dictionary 90 when selecting the combination of item character strings in the above-described step S304. By this reference, for example, a combination of item character strings in which a symbol “〒” relating to “zip code” is interposed between item characters is excluded from a set of item character string combinations that are character string conversion candidates. For example, when selecting a combination of item character strings that are candidates for character string conversion related to “telephone number”, the character string between the characters is not included in the contents of the tag element of the electronic document (for example, HTML document, XML document). Select a combination that is only in the column “-” (hyphen).

  In addition, each type of personal information is weighted for each notation pattern information, and the mask target determination unit 50 weights the character string interposed between the item character strings for each combination of the item character strings of the character string conversion candidates. You may make it calculate. Then, a combination of item character strings having the highest weighted calculation value is selected. Thereby, the mask accuracy of personal information is improved.

[Embodiment 3]
In the network system according to the third embodiment shown in FIG. 7, the character string conversion device 1 is installed in all the client terminals 2 existing in the system. The individual client terminals 2 have the hardware units cooperate with the software resources to implement the function units 20 to 60 and 80 of the character string conversion device 1 shown in FIG. The personal information notation pattern dictionary 90 is stored in the personal information notation pattern dictionary server 3.

  The client terminal 2 can communicate with the personal information notation pattern dictionary server 3 via the Internet 4. Personal information (for example, “name”, “phone number”, “mobile phone number”, “credit card number”, “zip code”, “mail address”, “address”) 201 of the client that owns the client terminal 2 is stored in advance in the personal information notation pattern dictionary 90. Stored in

  The client terminal 2 uses the personal information notation pattern dictionary 90 in the personal information notation pattern dictionary server 3 to mask the personal information included in the Web page browsing history data (execution of steps S1 to S4). Pull out 202 for reference. The personal information newly detected in the mask process is added to a new personal information notation pattern dictionary 90.

  In this network system, the Web browsing history collection server 5 can acquire the Web page browsing history data 203 from the client terminal 2 via the Internet 4. The personal information included in the Web page browsing history data 203 is subjected to mask processing by steps S1 to S4 executed by the client terminal 2.

[Aspect as Program of the Present Invention]
The present invention can be realized by configuring a program that causes a computer to function as a part or all of the functional units 20 to 60, 80, and 90 constituting the character string conversion device 1, and causing the computer to execute the program. Alternatively, it can be realized by configuring a part or all of the above-described steps S1 to S4 executed by the character string conversion device 1 with a program that is executed by the computer. Then, the computer can read the program, for example, FD (Floppy (registered trademark) Disk), MO (Magneto-Optical disk), ROM (Read Only Memory), memory card, CD (Compact Disk). -ROM, DVD (Digital Versatile Disk)-It can be recorded on ROM, CD-R, CD-RW, HDD, SSD, removable disk, etc., and can be stored or distributed. Furthermore, the above program can be provided via a network such as the Internet or e-mail.

DESCRIPTION OF SYMBOLS 1 ... Character string converter 30 ... Personal information dictionary 40 ... Personal information detection part 50 ... Mask object determination part 60 ... Mask replacement part

Claims (4)

Character string conversion device provided with a personal information dictionary in which personal information items are represented by large items and small items that detail these large items, and personal information character string data to be protected is stored for each small item of personal information Is a character string conversion method for converting personal information contained in an electronic document into another character string,
A procedure for detecting a character string of personal information of a small item included in the personal information dictionary from an electronic document as a character string conversion candidate character string;
If the detected candidate character string is not included in the contents of the tag elements of the electronic document from a set of combinations of small items in a large item same are different the candidate character strings, the number of characters between the candidate character strings Min A procedure for determining a combination of character strings as numbers as a target of character string conversion;
A character string conversion method comprising: replacing a combination of character strings determined to be the character string conversion target with another character string. Character string conversion device provided with a personal information dictionary in which personal information items are represented by large items and small items that detail these large items, and personal information character string data to be protected is stored for each small item of personal information Is a character string conversion method for converting personal information contained in an electronic document into another character string,
A procedure for detecting a character string of personal information of a small item included in the personal information dictionary from an electronic document as a character string conversion candidate character string;
If the detected candidate character string is not included in the contents of the tag element of the electronic document, the characters of the combination of candidate character strings from the set of candidate character string combinations having the same major item and different minor items A procedure for selecting a combination of character strings whose column length is shorter than the average character string length in the set and determining the selected combination as a target of character string conversion;
A character string conversion method comprising: replacing a combination of character strings determined to be the character string conversion target with another character string. Character string conversion device provided with a personal information dictionary in which personal information items are represented by large items and small items that detail these large items, and personal information character string data to be protected is stored for each small item of personal information Is a character string conversion method for converting personal information contained in an electronic document into another character string,
A procedure for detecting a character string of personal information of a small item included in the personal information dictionary from an electronic document as a character string conversion candidate character string;
When the detected candidate character string is not included in the contents of the tag element of the electronic document, the co-occurrence frequency in the electronic document is determined from a set of combinations of candidate character strings having the same large item but different small items . A procedure for determining the highest combination of character strings as a target for character string conversion,
A character string conversion method comprising: replacing a combination of character strings determined to be the character string conversion target with another character string.   The character string conversion program for making a computer perform each procedure of the character string conversion method of any one of Claim 1 to 3.

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