JP2016025412A - Modified region extraction system, modified region extraction method, and modified region extraction program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a modified region extraction system and such capable of identifying a modified region.SOLUTION: A modified region extraction system 101 includes: a modification information generation part 102 for generating modification information representing presence/absence of modification concerning combination information on the basis of a hash value calculated with respect to a combination information representing a combination concerning element information representing an element contained in target information 201; and a region identification part 103 for identifying a modified region 202 at target information on the basis of the modification information.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a modified area extraction system that can identify a modified area, for example.

  By modifying (tampering) a record (log) relating to processing performed by a computer program (hereinafter referred to as “program”) or an operation performed on the program or the like, the contents included in the record are not reliable. lose. For example, the modified log is not used as evidence material in a lawsuit or the like.

  As a technique for detecting alteration, there is a detection method using a hash value. The hash value is widely used as information indicating that the recorded content does not include alteration. For example, the techniques disclosed in Patent Documents 1 to 4 are examples of techniques for detecting alterations by using hash values.

  Patent Document 1 discloses a data processing device that detects a modification that changes the order of data. The data processing device generates an order alteration detection hash value capable of detecting an order alteration with respect to data adjacent to each other in the ordered data.

  Patent Document 2 discloses a hash generation device that generates a hash value capable of detecting deletion when the entire record is deleted. The hash generation device includes a first hash generation unit, a hash control unit, and a second hash generation unit. The first hash generation unit sequentially generates hash values for the input data. Next, the hash control unit generates a pair of two adjacent hash values among the hash values generated by the first hash generation unit. The second hash generation unit generates a new hash value for the hash value pair.

  Patent Document 3 discloses a verification device that detects falsification of data using a hash value. The verification device calculates a hash value for the ordered data based on a common key that is a basis for calculating a hash value, target data, and a hash value for data immediately before the target data. The verification device can detect that data has been tampered with with respect to a predetermined tamper pattern.

  Patent Document 4 discloses a management server that verifies an electronic signature using a hash value. The management server generates hash values for a plurality of signature data, and generates combined hash values by combining the generated hash values. Next, the management server verifies the signature data based on the combined hash value.

JP 2007-299961 A JP 2010-107832 A JP 2009-070026 JP JP 2011-142477 A

  Specifying the modified area in the log is a clue to estimating the intention of the operator who has made the modification. Furthermore, the fact that it is possible to specify a modified area in the log also contributes to preventing modification by the operator.

  Although the techniques disclosed in Patent Documents 1 to 4 can detect the presence or absence of modification using a hash value, the modified area cannot be specified. This is because these techniques detect only the presence or absence of modification based on the hash value.

  Accordingly, a main object of the present invention is to provide a modified region extraction system or the like that can specify a modified region.

  In order to achieve the above object, in one aspect of the present invention, a modified region extraction system has the following configuration.

That is, the modified region extraction system
Modification information generating means for generating modification information indicating whether or not there is a modification with respect to the combination information based on the hash value calculated for the combination information representing the combination regarding the element information indicating the element included in the target information;
And region specifying means for specifying element information modified in the target information based on the modification information.

As another aspect of the present invention, the modified region extraction method includes:
Using the information processing device, based on the hash value calculated for the set information representing the combination related to the element information indicating the element included in the target information, the modification information indicating the presence or absence of the change related to the set information is generated, and the modified information Based on the above, element information modified in the target information is specified.

  Furthermore, this object is also realized by such a modified region extraction program and a computer-readable recording medium for recording the program.

  According to the modified region extraction system and the like according to the present invention, a modified region can be specified.

It is a block diagram which shows the structure which the modification area | region extraction system which concerns on the 1st Embodiment of this invention has. It is a flowchart which shows the flow of the process in the modification area | region extraction system which concerns on 1st Embodiment. It is a figure showing an example of the data structure which object information has. It is a figure showing an example of the combination information produced | generated according to the predetermined | prescribed combination procedure. It is a figure showing an example of the combination information produced | generated according to the predetermined | prescribed combination procedure. It is a figure showing an example of the combination information produced | generated according to the predetermined | prescribed combination procedure. It is a figure which expresses an example of modification information notionally. It is a figure which represents notionally the example which specifies the element information changed based on modification information. FIG. 3 is a diagram conceptually illustrating an example of modification information and an example of specifying modified element information. It is a block diagram which shows the structure which the modification area | region extraction system which concerns on the 2nd Embodiment of this invention has. It is a flowchart which shows the flow of the process which calculates a hash value, in the modification area | region extraction system which concerns on 2nd Embodiment. It is a flowchart which shows the flow of the process which specifies element information in the modification area | region extraction system which concerns on 2nd Embodiment. It is a block diagram which shows roughly the hardware constitutions of the calculation processing apparatus which can implement | achieve the modification area | region extraction system which concerns on each embodiment of this invention.

  Next, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

<First Embodiment>
The configuration of the modified region extraction system 101 according to the first embodiment of the present invention and the processing performed by the modified region extraction system 101 will be described in detail with reference to FIGS. 1 and 2. FIG. 1 is a block diagram showing a configuration of a modified region extraction system 101 according to the first embodiment of the present invention. FIG. 2 is a flowchart showing the flow of processing in the modified region extraction system 101 according to the first embodiment.

  The modified region extraction system 101 according to the first embodiment includes a modified information generation unit 102 and a region specifying unit 103.

  First, the modification information generation unit 102 receives target information 201 having a data structure as exemplified in FIG. 3, for example. FIG. 3 is a diagram illustrating an example of a data structure included in the target information 201.

Referring to the example illustrated in FIG. 3, the target information 201 includes seven records associated with identifiers 1 to 7. In this example, one record includes three fields associated with identifiers of field 1 to field 3. That is, the target information includes element information associated with an identifier of F _mn (however, in the example shown in FIG. 3, 1 ≦ m ≦ 7, 1 ≦ n ≦ 3) regarding the record and the field. That is, in the example illustrated in FIG. 3, the target information 201 includes a plurality of element information indicating elements.

  In the example shown in FIG. 3, a record represents element information for one row, and a field represents element information for one column. Element information included in one record may be associated with each other. The element information included in the field may represent a value obtained by applying an operation associated with the field to information associated with the record. For example, when a field is associated with an operation “address”, the element information included in the field represents a region name, a street address, and the like.

  Note that the target information 201 does not necessarily include the number of records described above and the number of fields described above. That is, the number may be larger or smaller. That is, the number is not limited to the example described above.

Further, the target information 201 may include a hash value calculated based on the element information. In this case, as described later, the hash value does not necessarily have to be associated with one record. For example, hash value H ₄ need not be associated with record 4. The hash value may be a value calculated with respect to set information representing a combination of one or more pieces of element information.

  For convenience of explanation, hereinafter, it is assumed that the target information 201 has a data structure illustrated in FIG. In addition, it is assumed that the hash value included in the target information 201 is a value calculated according to the same algorithm as the hash value calculated in an embodiment described later.

  The modification information generation unit 102 generates modification information based on the hash value calculated for the combination information including the combination of element information determined according to a predetermined combination procedure among the element information included in the received target information 201. (Step S101).

  For example, the hash value is calculated according to an algorithm such as MD5 (Message Digest Algorithm 5) and SHA (Secure Hash Algorithm) -2. The above algorithm receives data having a length of 1 or more, and calculates a hash value having a fixed length according to the length of the received data. Since many procedures are known for calculating the hash value, description thereof is omitted here.

  For example, the modification information generation unit 102 determines whether the element information is modified based on, for example, a hash value calculated for the element information illustrated in FIG. 4 among the element information included in the received target information 201. Determine. FIG. 4 is a diagram illustrating an example of group information generated according to a predetermined combination procedure. The element information with a circle in FIG. 4 represents an example of element information included in certain set information.

For example, assume that the number of types of fields is three. The predetermined combination procedure is based on, for example, combination information obtained by combining the following information when calculating the hash value H _I (where I ≧ 5). That is,
_-Element information F _I1 included in the record I,
_-Element information F _I2 included in record I,
_-Element information F _I3 included in record I,
-Hash value H _{(I-1) for} record (I _-1) ,
Element information F _{(I-2) 3} regarding the record (I-2)
Element information F _{(I-3) 2} regarding the record (I-3)
Element information F _{(I-4) 1} regarding the record (I-4).

For example, H ₅ is calculated for the set information including F ₅₁ , F ₅₂ , F ₅₃ , H ₄ , F ₃₃ , F ₂₂ , and F ₁₁ .

  The records (I-4) to I may be stored in a buffer (storage area) capable of storing information included in the records. That is, in this case, the buffer can store five records. The modification information generation unit 102 generates modification information from a record stored in the buffer according to a predetermined combination procedure.

For example, as illustrated in FIG. 5, the hash value H ₆ is calculated for the set information including F ₆₁ , F ₆₂ , F ₆₃ , H ₅ , F ₄₃ , F ₃₂ , and F ₂₁ . FIG. 5 is a diagram illustrating an example of set information generated according to a predetermined combination procedure. The element information with a circle in FIG. 5 represents an example of element information included in a certain set of information.

That is, in the example described above, if it has a number of types of object information 201 is more fields, for example, the hash value H _I is based on the set information that is a combination of information shown below. That is,
・ Element information F _Im ,
-Hash value H _(I-1) ,
Element information F _{(Im-1) (NF-m-1)}
(However, 1 ≦ m ≦ NF (number of types of fields)).

  Further, the predetermined combination procedure may be a procedure illustrated in FIG. FIG. 6 is a diagram illustrating an example of set information generated according to a predetermined combination procedure. The element information with a circle in FIG. 6 represents an example of element information included in certain set information.

In the example shown in FIG. 6, for example, H _I is F _I1 , F _I2 , F _I3 , H _(I-1) , F _{(I-2) 1} , F _{(I-3) 2} , and F _{(I -4)} Calculated for group information including ₃ .

That is, in the example described above, if it has a number of types of object information 201 is more fields, for example, the hash value H _I is based on the set information that is a combination of information shown below. That is,
・ Element information F _Im ,
-Hash value H _(I-1) ,
-Element information F _{(Im-1) m} ,
(However, 1 ≦ m ≦ NF (number of types of fields)).

  The group information may be information (data) having a certain length.

  Further, according to the predetermined combination procedure described above, the combination information related to one element information is a fixed number of times (in this case, twice). Therefore, the number of times element information overlaps between a plurality of pieces of group information is small. Therefore, in this case, according to the modified region extraction system 101 according to the present embodiment, the modified region can be efficiently identified according to the processing described later.

  Next, the modification information generation unit 102 determines whether or not the element information included in the combination information has been modified according to the hash value calculated for the combination information included in the received target information. For example, when the target information includes a hash value related to the set information, the modification information generation unit 102 determines whether or not the hash value matches the hash value calculated for the set information.

  When the modification information generation unit 102 determines that the two hash values match, the modification information generation unit 102 determines that the combination information has not been modified. Further, when the modification information generation unit 102 determines that the two hash values do not match, the modification information generation unit 102 determines that the combination information has been modified. The modification information generation unit 102 generates modification information (for example, FIG. 7) indicating the presence or absence of the modification by determining the presence or absence of the modification with respect to each set information included in the target information (step S101). FIG. 7 is a diagram conceptually illustrating an example of modification information.

In the example illustrated in FIG. 7, the modification information includes element information, a hash value, and information indicating whether or not the hash value matches the calculated hash value, but the element information, the hash value, Need not be included. That is, the modification information may include information indicating whether or not they match. For example, in the example illustrated in FIG. 7, the modification information generation unit 102 represents that the group information regarding the hash value H ₅ and the group information regarding H ₇ have been modified (triangle marks). In addition, in the example illustrated in FIG. 7, the modification information generation unit 102 generates modification information indicating that the pair information regarding the hash values H _{1 to} H ₄ and H ₆ has not been modified.

In this case, for example, set information associated with the hash value H ₆ represents that it has not been altered. That is, the element information included in the set information indicates that it has not been altered. Further, for example, set information associated with the hash value H ₅ indicates that has been modified. That is, the element information included in the set information indicates that it has been altered.

  Note that record (Im) (where 1 ≦ m ≦ NF) -1 to record I may be stored in a buffer capable of storing information included in the record. That is, in this case, the buffer can store (NF + 2) records. The modification information generation unit 102 generates modification information from a record stored in the buffer according to a predetermined combination procedure.

  Next, the area specifying unit 103 specifies element information that has been modified in the received information based on the modification information (step S102). That is, the area specifying unit 103 specifies the altered area 202 in the input target information 201.

When the combination information is generated according to a predetermined combination procedure, the area specifying unit 103 specifies combination information related to a specific hash value and element information included in the combination information. For example, the area specifying unit 103, the hash value _{H 5} is set information _{F 51, F 52, F 53} , H 4, F 33, F 22, and _a hash value for _{F 11,} out of said set information, Identify that at least one has been modified. Similarly, the area specifying unit 103, the hash value _{H 7} is set information _{F 71, F 72, F 73} , H 6, F 53, F 42, and _a hash value for _{F 31,} out of said set information , Specify that at least one has been modified.

In this case, as illustrated in FIG. 8, the region specifying unit 103 specifies that F ₅₃ included in common in the two sets of information that has been modified is the modified element information. FIG. 8 is a diagram conceptually illustrating an example of specifying the modified element information based on the modification information.

  In FIG. 8, a triangle mark attached to the hash value indicates that the set information regarding the hash value has been altered. A triangle mark added to the element information indicates that the element information is identified as having been altered.

  In addition, a process of specifying the modified element information by the area specifying unit 103 will be described with reference to the example illustrated in FIG. FIG. 9 is a diagram conceptually illustrating an example of modification information and an example of specifying modified element information.

  In FIG. 9, a triangle mark attached to the hash value indicates that the pair information relating to the hash value has been altered. A triangle mark added to the element information indicates that the element information is identified as having been altered.

In the case of the example illustrated in FIG. 9, the area specifying unit 103 has the hash values H ₅ , H ₇ , and H ₈ modified, and the hash values H _{1 to} H ₄ and H ₆ are not modified. The element information is specified based on the modification information.

In this case, as described above, the area specifying unit 103 includes the element information included in the set information regarding the hash value H ₅ (hereinafter referred to as “set information H ₅ ”) and the set information regarding the hash value H ₇ ( Hereinafter, element information included in “set information H ₇ ” is specified. Further, the area specifying unit 103, the hash value _{H 8} is set information _{F 81, F 82, F 83} , H 7, F 63, F 52, and _a hash value for _{F 41,} out of said set information, Identify that at least one has been modified. Hereinafter, the set information related to the hash value H ₈ is represented as “set information H ₈ ”.

  Next, the area specifying unit 103 extracts at least element information included in common with the plurality of pieces of set information regarding the set information regarding the three modified hash values.

For example, the area specifying unit 103 extracts that the element information included in common to the set information H ₅ and the set information H ₇ is F ₅₃ . Furthermore, the area specifying unit 103 extracts that the element information included in common in the set information H ₅ and the set information H ₈ is F ₅₂ . Further, the region specifying unit 103 specifies that there is no element information included in common in the set information H ₇ and the set information H ₈ . Next, the area specifying unit 103 specifies the extracted element information (that is, F ₅₂ and F ₅₃ ) as modified element information.

  The area specifying unit 103 may extract element information included in three or more pieces of group information as modified element information.

  The area specifying unit 103 specifies the modified element information based on the combination information that is determined to be modified in the modification information, but the combination information that is determined not to be modified, or these two types Element information may be specified based on the combination of the group information.

  Further, the predetermined combination procedure generates a combination that can specify a smaller number of pieces of element information than element information included in each piece of set information based on a plurality of pieces of set information that are specified as being modified. Any procedure can be used.

  Next, effects related to the modified region extraction system 101 according to the first embodiment will be described.

  According to the modified region extraction system 101, the modified region 202 can be specified.

  This is because the element information is specified based on the set information in which the area specifying unit 103 has been changed or the set information that is determined not to be changed.

  For example, when certain specific element information has been modified, the modified information generation unit 102 compares the above two hash values and the like, and the combination information including the specific element information has been modified. judge. In this case, the modification information is information indicating whether the set information includes the specific element information.

  Next, the region specifying unit 103 specifies element information that has been modified in the target information by extracting element information included in the modified group information based on the modification information.

  Also, for example, when the predetermined combination procedure is the above-described method, the modified region extraction system 101 according to the present embodiment specifies specific element information with hash values corresponding to the number of records. Can do.

  On the other hand, a hash value is calculated for each record, and specific element information can be specified based on the hash value. However, in this case, the number of times the hash value is calculated is (number of records × number of types of fields). This number is greater than the number of records when the number of types of fields is greater than two. Therefore, according to the modified region extraction system 101 according to the present embodiment, specific element information can be specified efficiently.

<Second Embodiment>
Next, a second embodiment of the present invention based on the first embodiment described above will be described.

  In the following description, the characteristic parts according to the present embodiment will be mainly described, and the same components as those in the first embodiment described above will be denoted by the same reference numerals, and redundant description will be omitted. To do.

  The configuration of the modified region extraction system 111 according to the second embodiment and the processing performed by the modified region extraction system 111 will be described with reference to FIGS. FIG. 10 is a block diagram showing a configuration of the modified region extraction system 111 according to the second embodiment of the present invention. FIG. 11 is a flowchart showing a flow of processing for calculating a hash value in the modified region extraction system 111 according to the second embodiment. FIG. 12 is a flowchart showing a flow of processing for specifying element information in the modified region extraction system 111 according to the second embodiment.

The modified area extraction system 111 according to the second embodiment includes a hash value calculation unit 112, a set information generation unit 113, a modification information generation unit 114, and an area specification unit 103.
Have

  First, the flow of processing in which the modified area extraction system 111 calculates a hash value will be described.

  The set information generation unit 113 generates set information by combining a plurality of element information according to the predetermined combination procedure described above (step S111). In this case, the set information generation unit 113 may further combine the calculated hash values. By combining hash values, the modified area extraction system 111 can further detect modification such as deletion of a record.

  Next, the hash value calculation unit 112 calculates a hash value related to the set information based on the set information and the key information (hash key) (step S112). The hash value calculation unit 112 may store the calculated hash value, for example, as a log in a storage device such as a database, together with information that is a target for calculating the hash value.

  In this case, the key information is information relating to numerical values calculated according to a predetermined calculation procedure. In this case, the key information should be different from each other. For example, the predetermined calculation procedure may be a procedure for calculating the read numerical values by sequentially reading the numerical values from a predetermined numerical sequence. The predetermined calculation procedure may be a procedure for calculating a pseudo random number. Since various methods are known for calculating the pseudo random number, detailed description thereof is omitted here. Furthermore, the key information may change as a hash value related to one set information is calculated. For example, the key information may be a value calculated according to a procedure for calculating a pseudo random number in accordance with the calculation of the hash value.

  When the key information is calculated according to the procedure for calculating the pseudo random number in accordance with the calculation of the hash value related to one set information, the modified region extraction system 111 according to the present embodiment further modifies the key information. Has the effect of becoming difficult. This is because the procedure for calculating the hash value differs depending on the set information.

  Next, a process flow in which the modified region extraction system 111 specifies element information will be described.

  The set information generation unit 113 generates set information by combining a plurality of element information in accordance with the predetermined combination procedure described above (step S115). In this case, the set information generation unit 113 generates set information according to a procedure similar to the procedure for calculating a hash value for information that is a target for detecting modification.

  Next, the modification information generation unit 114 generates modification information regarding the group information generated by the group information generation unit 113 (step S116). In this case, the modification information generation unit 114 may generate modification information in response to the combination information generation unit 113 sequentially generating combination information, or the combination information generation unit 113 may generate a plurality of pieces of combination information. The modification information may be generated in response to the generation.

  Next, the area specifying unit 103 specifies the modified element information based on the modification information (step S102).

  Next, effects related to the modified region extraction system 111 according to the second embodiment will be described.

  According to the modified region extraction system 111 according to the present embodiment, in addition to being able to specify the modified region, it further provides a strong deterrent against modification related to logs and the like.

The reason is Reason 1 and Reason 2. That is,
(Reason 1) The configuration of the modified region extraction system 111 according to the second embodiment includes the configuration of the modified region extraction system 101 according to the first embodiment.
(Reason 2) This is because the key information changes as the hash value is calculated.

  That is, in the above-described example, the procedure for calculating the hash value differs depending on the set information. Even if one key information is leaked, the procedure for calculating the hash value is different, so that the hash value relating to different set information cannot be modified. Therefore, according to the modified region extraction system 111 according to the present embodiment, it is a strong deterrent against modification related to logs and the like.

(Hardware configuration example)
A configuration example of hardware resources that implements the modified region extraction system in each embodiment of the present invention described above using one calculation processing device (information processing device, computer) will be described. However, the modified region extraction system may be realized using at least two calculation processing devices physically or functionally. Such a modified region extraction system may be realized as a dedicated device.

  FIG. 13 is a diagram schematically illustrating a hardware configuration of a calculation processing apparatus capable of realizing the modified region extraction system according to the first embodiment or the second embodiment. The computing device 20 includes a central processing unit (Central Processing Unit, hereinafter referred to as “CPU”) 21, a memory 22, a disk 23, and a nonvolatile recording medium 24. The calculation processing device 20 further includes an input device 25, an output device 26, and a communication interface (hereinafter referred to as “communication IF”) 27. The calculation processing device 20 can transmit / receive information to / from other calculation processing devices and communication devices via the communication IF 27.

  The nonvolatile recording medium 24 is, for example, a compact disc (Compact Disc) or a digital versatile disc (Digital_Versatile_Disc) that can be read by a computer. The nonvolatile recording medium 24 may be a Blu-ray Disc (registered trademark), a universal serial bus memory (USB memory), a solid state drive (Solid State Drive), or the like. The non-volatile recording medium 24 retains such a program without being supplied with power, and can be carried. The nonvolatile recording medium 24 is not limited to the above-described medium. Further, the program may be carried via the communication network via the communication IF 27 instead of the nonvolatile recording medium 24.

  That is, the CPU 21 copies a software program (computer program: hereinafter simply referred to as “program”) stored in the disk 23 to the memory 22 when executing it, and executes arithmetic processing. The CPU 21 reads data necessary for program execution from the memory 22. When the display is necessary, the CPU 21 displays the output result on the output device 26. When inputting a program from the outside, the CPU 21 reads the program from the input device 25. The CPU 21 interprets and executes the modified region extraction program (FIG. 2, FIG. 11, or FIG. 12) in the memory 22 corresponding to the function (process) represented by each unit shown in FIG. 1 or FIG. To do. The CPU 21 sequentially performs the processes described in the above-described embodiments of the present invention.

  That is, in such a case, it can be understood that the present invention can also be achieved by such a modified region extraction program. Furthermore, it can be understood that the present invention can also be realized by a computer-readable non-volatile recording medium in which such a modified region extraction program is recorded.

DESCRIPTION OF SYMBOLS 101 Modified area extraction system 102 Modified information generation part 103 Area specification part 201 Target information 202 Modified area 111 Modified area extraction system 112 Hash value calculation part 113 Set information generation part 114 Modification information generation part 20 Computation processing apparatus 21 CPU
22 Memory 23 Disk 24 Non-volatile recording medium 25 Input device 26 Output device 27 Communication IF

Claims (10)

Modification information generating means for generating modification information indicating whether or not there is a modification with respect to the combination information based on the hash value calculated for the combination information representing the combination regarding the element information indicating the element included in the target information;
A modified region extraction system comprising: region identifying means for identifying element information modified in the target information based on the modified information. Set information generating means for generating the set information according to a predetermined combination procedure;
Based on the set information and key information that is part of a procedure for calculating the hash value, further comprising: a hash value calculation means for calculating the hash value;
The modified region extraction system according to claim 1, wherein the modification information generation unit generates the modification information with respect to the group information generated by the group information generation unit. 3. The modified region extraction system according to claim 2, wherein in the predetermined combination procedure, all of the set information includes each of the element information a predetermined number of times. The modified area extraction system according to claim 2 or 3, wherein the hash value calculation means calculates the hash value based on the key information that changes according to the set information. The modified region extraction system according to claim 2 or 3, wherein the hash value calculation means calculates the hash value according to the key information generated according to a pseudo random number. 6. The modified region extraction according to claim 2, wherein the set information generation unit generates the set information including the combination and a hash value related to a combination different from the combination. system.   Using the information processing device, based on the hash value calculated for the set information representing the combination related to the element information indicating the element included in the target information, the modification information indicating the presence or absence of the change related to the set information is generated, and the modified information Based on the above, the modified region extraction method is characterized in that element information modified in the target information is specified. A modification information generation function for generating modification information indicating presence / absence of modification relating to the combination information, based on a hash value calculated for the combination information representing the combination regarding element information indicating an element included in the target information;
A modified region extraction program that causes a computer to realize a region identifying function that identifies element information modified in the target information based on the modified information. A set information generation function for generating the set information according to a predetermined combination procedure;
Based on the set information and key information that is a part of a procedure for calculating the hash value, a hash value calculation function for calculating the hash value is realized in a computer.
The modified region extraction program according to claim 8, wherein the modification information generation function generates the modification information with respect to the group information generated according to the group information generation function. The modified region extraction program according to claim 9, wherein, in the predetermined combination procedure, all of the combination information includes each element information a predetermined number of times.

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