JP4226447B2 - How to verify digital signature - Google Patents

Description

  The present invention relates to a method for verifying the contents of an electronic signature, and in particular, verifies whether information visualized on digital data is derived from information included in the electronic signature for the purpose of visualization. The present invention relates to a method for verifying the contents of a visualized electronic signature.

  More specifically, the present invention is visualized when digital signature is applied to digital data, and information to be visualized included in the digital signature is visualized in a display area provided at an arbitrary position on the digital data. The present invention relates to a method for verifying whether or not the content that has been visualized is information that should be visualized in an electronic signature.

  After requesting and implementing digital signatures from the center server for various types of digital data, the main information of the digital signature is obtained by visualizing some information on the digital data to be signed on the digital data to be signed. There is a request to clarify the contents.

  For example, an electronic time stamp for certifying when a certain digital data exists and has not been changed after that is a kind of electronic proof. This is for signing digital data to be certified.

In this case, the time information included in the signature can be confirmed by verifying the signature, but once verified, it can be confirmed that the time and data signed are not changed from that point. After that, it is preferable that the signed time can be easily confirmed without performing verification work one by one. To realize this, it is conceivable to visualize the time information included in the signature in the digital data to be signed. Proposes “a time stamp stamping system for an electronic document and its program medium” disclosed in Japanese Patent Application Laid-Open No. 2003-228561.
JP 2003-244139 A

  The above-mentioned patent document 1 calculates a non-collisional digest value such as a hash value, for example, except for an electronic signature embedding part and a data visualization area, and also includes information to be included in the electronic signature and a digest. It can be proved that no change has been made to the digital data to be signed since the digital signature whose values are unified by encryption is performed.

  However, the display area that visualizes the information (time information in this case) that is included in the electronic certification (to be visualized) is not subject to the digest value, so a special program is used to display the display area. Since the digest value does not change even if the contents of the information visualized in the display area is changed or altered by rewriting or partially overwriting the characters and numbers of the information visualized in Changes and tampering cannot be detected. Therefore, when verifying the electronic signature, it is necessary to compare and verify information visualized in the display area, that is, display time and information intended for display included in the electronic signature, for example, time information. .

  The present invention has been made in view of the above points, and an object of the present invention is to provide a method for comparing and verifying information visualized in a display area and information to be visualized included in an electronic signature.

(1) In order to achieve the above object, the electronic signature content verification method of the present invention can be applied to an electronic signature by using dedicated electronic signature processing software as described in claim 1. Verification software that verifies an electronic signature that enables visualization of the contained information in a display area provided on the digital data to be signed, and an information processing terminal in which this verification software is installed In the electronic signature verification system, the verification software includes information reading means for reading out information intended for visualization included in the electronic signature from the electronic signature, and information obtained by extracting the read information intended for visualization Information expanding means for expanding the information visualized in the area to the storage unit of the information processing terminal and the reading expanded to the storage unit of the information processing terminal Information comparing means for comparing the information intended for visualization with the information visualized in the extracted display area, and verifying the validity of the electronic signature only when the comparison results match It is a feature.

(2) Further, in the electronic signature content verification method according to the present invention, as described in claim 2, the information comparison unit performs visualization that is read from the electronic signature and developed in the storage unit of the information processing terminal. Data that is converted into the information format visualized in the display area and converted into data format that has been visualized in the display area and newly developed in the storage unit of the information processing terminal, and in the display area The information is compared with the data developed in the storage unit of the information processing terminal from which the information is extracted.

(3) Further, in the electronic signature content verification method according to the present invention, as described in the third aspect, the information comparing means extracts from the display area on the digital data and develops it in the storage unit of the information processing terminal. The data visualized in the displayed display area is converted to the format of the information intended for visualization included in the electronic signature, and then converted into a storage unit of the information processing terminal. It is characterized in that the data that is included in the electronic signature and the information intended for visualization are read out and compared with the data developed in the storage unit in the information processing terminal.

  According to the means described in the above (1) to (3), the information included in the electronic signature for visualization purpose is visualized in a display area provided at an arbitrary position on the digital data. It is possible to verify whether the information reflected in the display area or the information visualized in the display area is derived from the information intended for visualization included in the electronic signature, Information intended for visualization included in the electronic signature in addition to the verification of the electronic signature described in Patent Document 1, using an information processing terminal in which electronic signature verification software is installed as means for verification Is converted into data in the same format as the information visualized in the display area, and developed in the storage unit of the information processing terminal. This conversion means may adopt a method in which the electronic signature software converts the information included in the electronic signature for the purpose of visualization into information for visualization in the display area. In addition, the information visualized in the display area is extracted and expanded in the storage unit, and both data expanded in the storage unit are compared and verified. It is determined that the information included in is visualized.

  It is also conceivable that the information visualized in the display area is converted into data of the same format as the information intended for visualization included in the electronic signature, and then compared with the information intended for visualization.

  The electronic signature content verification method according to the present invention verifies whether the content of the electronic signature is correctly displayed, so that the information that is actually displayed in the display area is included in the electronic signature. Since it is possible to determine the authenticity of whether or not the information is derived from the information, it is possible to obtain an electronic signature method that can display information included in the electronic information for the purpose of visualization on the digital data. .

  Hereinafter, a method for verifying the contents of an electronic signature according to an embodiment of the present invention will be described with reference to the drawings, taking an electronic signature including time information derived from a center server, that is, a digital time stamp as an embodiment.

  FIG. 1 shows a schematic configuration of a system for realizing a method according to an embodiment of the present invention, in which 10 is a center server as an external organization, and 20 is an information processing terminal of a client. The center server includes a reference clock 11 such as an atomic clock for accurately and fair time, and an electronic signature issuing server 12 that can be connected to the network 40. In some cases, an electronic signature verification server 13 for verifying an electronic signature that can be connected to the network 40 may be included. The reference clock 11 gives an accurate and fair time to the electronic signature issuing server. Although not shown, the reference clock 11 can be continuously audit-calibrated with a clock owned by NTA (National Time Authority), for example, an atomic clock that defines Japan Standard Time of the Communications Research Laboratory in Japan. It is desirable.

  The information processing terminal 20 of the client is connectable to the network 40 and has an electronic signature generation software installed. The time stamp for the digital data that the client is generating or processing in the information processing terminal 20 is electronic signature issuing server 12 The electronic signature including the time information derived from the returned reference clock 11 (hereinafter, the time stamp token 17) can be reflected in the digital data and stored as new digital data.

  The client transmits the digital data with the electronic signature to the third party information processing terminal 30 by transmitting the digital data via the network 40 or sending the data recorded on the physical recording medium 50, and the third party The digital data can be browsed on the information processing terminal 30. When the time stamp verification software is installed in the information processing terminal 30 of the third party, it is possible to verify the authenticity and validity of the time stamp on the information processing terminal 30. Alternatively, as another verification method, the digital data is transmitted to the electronic signature verification server 13 owned by the center server 10 via the network 40, and the electronic signature verification server 13 verifies the authenticity and validity of the time stamp, By returning the verification result of the electronic signature together with the digital data to the third party information processing terminal 30 via the network 40, the time stamp can be verified.

  FIG. 2 is installed in the information processing terminal 20 of the client in order to request the digital signature issuing server 12 of the center server 10 to issue an electronic signature including time information, that is, a time stamp token 17 to the digital data. It is a conceptual diagram of the process which the electronic signature production | generation software which has run.

  The client opens the digital data 60 subject to the electronic signature on the information processing terminal 20 in which the electronic signature generation software owned by the client is installed, and makes the workable state. In this embodiment, the electronic signature is a time stamp including accurate and fair time information. Next, the electronic signature generation software is activated and a time stamp generation process for the digital data 60 is executed. The electronic signature generation software displays a temporary imprint of the time stamp, and the client performs a determination operation by placing the imprint at a desired position. At this time, dummy time information is used for the provisional seal in order to secure an area of time information to be written after reflecting the electronic signature. By this operation, a display area 62 for displaying the stamp imprint is generated.

  Next, the electronic signature generation software, as shown in FIG. 2, an area for embedding an electronic signature in the digital data 60, that is, an electronic signature field 63, and a display area definition information field for defining the position and data size of the display area 62. 64 is added, and digital data 61 different from the digital data 60 to be signed is newly generated. At this point, no data exists in the electronic signature field 63. The electronic signature field 63 and the display area definition information field 64 exist only as data, and are not visualized.

  Further, as shown in FIG. 2, the electronic signature generation software generates data (hereinafter referred to as a digest) of the newly generated digital data 61 by combining the original data area excluding the display area 62 and the display area definition information field 64. A digest value such as a hash value using a hash function is calculated for the target area 65), and the obtained digest value 66 (see FIG. 1) is sent via the network 40 to the electronic signature issuing server of the center server 10. 12, a digital signature request for the digital data 60 is made.

  Upon receiving the digest value 66 of the digest target area 65, the electronic signature issuing server 12 receives the digest value 66 and the digest information derived from the reference clock 11 of the center server 10 as shown in FIG. Then, the electronic signature information 16 having a readable configuration is generated, and a time stamp token 17 is generated by encrypting with the private key 15 owned by the electronic signature issuing server 12 itself, and returned to the information processing terminal 20 of the client. . At this time, a public key 18 for decrypting the time stamp token 17 may be attached and returned.

  As shown in FIG. 4, the information processing terminal 20 of the client and the electronic signature generation software installed are distributed and owned by the public key 18 attached with the returned time stamp token 17 or by the center server in advance. The public key 18 is decrypted. Furthermore, the dummy time information in the display area 62 is overwritten with the data obtained by converting the time information 14 obtained by the decryption into the visualization information 67 using the data conversion means 22 belonging to the electronic signature generation software. As a result, the time information derived from the reference clock of the center server is visualized, and the time information that proves the existence time of the digital signature target digital data 60 can be displayed on the digital data 61.

  Next, the information processing terminal 20 and the installed electronic signature generation software overwrite the time stamp token 17 on the electronic signature field 63 on the digital data 61 as shown in FIG. The generated digital data 68 is generated. In some cases, the public key 18 for decryption may also be recorded in the electronic signature field 63. Through the above processing, the digital data 68 to which the digital time stamp 69 for verifying the time of existence of the digital signature target digital data 60 is created.

  The client applies the digital time stamp 69 to a third party by sending the digital data 68 with the time stamp 69 as shown in FIG. 1 via the network 40 or recording it on the physical recording medium 50 and sending it. The digital data 68 is passed. The digital data 68 can be browsed by opening on the information processing terminal 30 owned by a third party. The third party can verify not only the data browsing but also the authenticity and validity of the digital time stamp by the following method.

  That is, the third party connects the information processing terminal 30 to the electronic signature verification server 13 of the center server 10 via the network 40 and transmits the digital data 68 to be verified. As in step 1 of FIG. 5, the electronic signature verification server 13 extracts the time stamp token 17 recorded in the electronic signature field 63 of the received digital data 68, and the public key 18 owned by the electronic signature verification server 13 or Then, decryption is performed using the public key 18 recorded in the digital signature field 63 of the digital data 68 so that the digest value 66 of the digest target area and the time information 14 can be read out.

  In addition, the electronic signature verification server 13 performs the digest target area of the digital data 68 transmitted first, that is, from the digital data 68 to the electronic signature field 63 area and display area on its own storage device as in step 2 of FIG. The digest value is calculated for data other than 62, and the recalculated digest value 71, which is the calculation result obtained as in step 3 of FIG. 5, and the digital data 68 obtained by decrypting the time stamp token 17 are obtained. The digest value 66 of the digest target area recorded in the above is compared using the comparison means 70. If the comparison result matches, it can be confirmed that the digital data 68 has exactly the same contents other than the imprint of the time stamp 69 in the visible data portion of the digital signature target digital data 61 immediately before the digital signature is applied. It can be proved that the data 68 has not been falsified or altered since the time stamp 69 is implemented. And further verification continues. If the comparison results do not match, the digital data 68 cannot be authenticated because some processing has been added to the data after the time stamp 69 is applied. Accordingly, the authentication is denied and the process is terminated.

  Next, the electronic signature verification server 13 uses the electronic signature generation software installed in the information processing terminal 20 of the client, as shown in step 1 of FIG. The same conversion means 72 as the data conversion means 22 is used to convert the virtual display data 73 in the same format as the time information 67 visualized in the display area 62. Then, as shown in the procedure 2 of FIG. 6, the comparison is made with the visualized time information written in the display area 62 of the digital data 68, that is, the actual display data. If the comparison results match, the time information 14 (see FIG. 3) certifying the digital signature target digital data 60 recorded in the time stamp token 17 is correctly displayed in the seal of the digital data 68. Will be. If they do not coincide with each other, the time information displayed in the seal stamp is modified by some method, and the digital data 68 cannot be authenticated. Accordingly, the authentication is denied and the process is terminated.

  FIG. 7 shows a specific example of the data conversion means 22 or 72 shown in FIGS. For example, when the time information 90 recorded in the time stamp token 17 in the UNIX (registered trademark) system time format is placed in () of “32”, which is a 32-bit C language function “strftime ()” 91, ASCII characters It is converted into time information 92 by a column.

As described above, the authenticity of the digital data 68 itself is proved at the stage where the non-falsification verification by comparing the digest values and the authenticity of the displayed time information can be confirmed. In this embodiment, the time information 14 recorded in the time stamp token 17 is recorded in the time stamp token 17 in the verification of whether the time information 14 correctly matches the time information 69 displayed in the display area 62 on the digital data 68. The time information 14 is converted into the time information 73 visualized in the display area 62 using the data conversion means 72. However, the time information 73 is converted into the same format as the time information 14 using another conversion means. Data may be converted and compared.
In this embodiment, the verification work is performed by the electronic signature verification server 13 of the center server 10. However, if the electronic signature verification software is installed, verification is performed on the information processing terminal 30 of a third party. It is also possible.

  FIG. 8 is a flowchart in the case where verification of the digital data 68 is executed by the information processing terminal 30 owned by a third party. As shown in FIG. 8, in step S1, the operator opens the digital data 68 to which the electronic signature has been applied, and starts the signature verification program in step S2. In step S3, the information processing terminal 30 calculates the digest value of the digest target area using the electronic signature verification software. The digest target area is data obtained by combining the original data area excluding the display area 62 and the definition information field 64 of the display area. Subsequently, in step S4, the time stamp token 17 recorded in the digital signature field 63 of the digital data 68 is decrypted with the public key 18, and the digest value 66 of the digest target area of the digital data 68 immediately before the digital signature is extracted. Next, the digest value newly calculated in step S5 is compared with the digest value recorded in the time stamp token 17.

  If both digest values match in step S6, the process proceeds to step S7 and further verification is continued. In step S7, the time information 14 recorded in the time stamp token 17 is read. Next, the time information 14 read in step S8 is converted into the same data format as the time information displayed in the display area 62 of the digital data 68 by using the data conversion means 72, and virtual display data is created. Subsequently, the actual display data displayed in the display area 62 of the digital data 68 is extracted in step S9, and the real and virtual display data are compared by the comparison means 70 in step S10.

  If they match in step S11, the digital data 68 is not touched after the digital signature 68 is digitally signed in step S12. At the same time, the time information 69 displayed in the display area 62 is a time stamp token. Since the time information 14 is the same as the time information 14 recorded in FIG. 17, the digital signature of the digital data 68 is authenticated, and the fact is displayed on the information processing terminal 30 in step S13, and the operation is terminated.

  On the other hand, if they do not match in step S6, the digital data 68 has been processed by a person after the digital signature has been applied, so the digital signature is denied in step S14, and in step S15. The fact is displayed on the information processing terminal 30 and the operation is terminated. If they do not match in step S11, the time information 69 displayed in the display area 62 of the digital data 68 is different from the time information 14 recorded in the time stamp token 17, and therefore step S16. In step S17, the information processing terminal 30 displays that fact and terminates the operation.

  In short, according to the present invention, the center server 10 receives a digest value 66 of a document or various digital data in response to a request from a client, generates an electronic signature for the digest value 66, and then generates a digest value and electronic signature information. In the center server type electronic signature service configured so that the information included in the electronic signature can be viewed on the target digital data at the same time as the digest value is reflected in the digital data to be signed and returned to the client. It is verified whether the information visualized on the digital data is derived from the information intended for visualization included in the electronic signature.

  In addition, when verifying an electronic signature that can visualize the information to be visualized included in the electronic signature on the target digital data of the electronic signature, in addition to the normal verification of the electronic signature, It is necessary to verify whether or not the visualized information is a visualization of information intended for visualization included in the electronic signature.

  The method of verification is to convert the data written in the area for recording information for visualization in the electronic signature into data in the same format as the display data by the data conversion program by the dedicated signature verification software, Compare with the information visualized on the digital data to be signed.

  Alternatively, the information visualized on the digital data to be signed is converted into data in the same format as the information intended for visualization in the electronic signature by another data conversion program, and the visualization in the electronic signature is intended. Compare with the data written in the information recording area.

  The information to be visualized included in the electronic signature is reflected in the information visualized in the display area provided at an arbitrary position on the digital data, or the information visualized in the display area is the electronic signature. As a means of verifying whether it is derived from the information to be visualized included in the information terminal device in which the electronic signature verification software is installed, the information to be visualized included in the electronic signature is displayed in the display area. The data is converted into data in the same format as the visualized information, and is developed in the storage unit of the information processing terminal device.

  This conversion means may adopt the method of converting the information to be visualized included in the electronic signature into information for visualization in the display area. In addition, the information visualized in the display area is extracted and similarly expanded in the storage unit, and both data expanded in the storage unit are compared and verified. The purpose is to visualize in the display area only when they match. Judge that the information is visualized.

The schematic block diagram regarding the electronic signature structure of the system by the Example of this invention, and the memory | storage part of an information processing terminal. The conceptual diagram of the process which the electronic signature software by the Example of this invention performs. Explanatory drawing which shows the specific implementation method of the electronic signature in the verification method of the electronic signature content by the Example of this invention. Explanatory drawing which shows the reflection method of the electronic signature in the verification method of the electronic signature content by the Example of this invention. Explanatory drawing explaining the procedure of the verification of the electronic signature content in the verification method of the electronic signature content by the Example of this invention. Explanatory drawing explaining the procedure of the verification of the electronic signature content in the verification method of the electronic signature content by the Example of this invention. The block diagram of the data conversion of the verification method of the electronic signature content by the Example of this invention. The operation | movement flowchart of the verification method of the electronic signature content by the Example of this invention.

Explanation of symbols

10 ... Center server
11 ... Reference clock
12 ... Electronic signature issuing server
13 ... Digital signature verification server
14 Time information
15 ... Secret key
16 ... Electronic signature information
17 ... Timestamp token
18 ... Public key
20: Client information processing terminal
22 Data conversion means
30 ... Third party information processing terminal
40 ... Network
50. Physical recording medium
60 ... Digital data
61 ... Digital data
62 ... Display area
63 ... Electronic signature field
64 ... definition information field
66 ... digest value
67 ... Visualization information
68 ... Digital data
69 ... Time stamp (time information)
70: Comparison means
72. Data conversion means
73 ... Virtual display data
90 ... Time information before conversion
91 ... Conversion function
92 ... Time information after conversion

Claims (3)

Verification that verifies the digital signature that makes it possible to visualize and display the information contained in the digital signature in the display area provided on the digital data to be signed by using dedicated digital signature processing software In an electronic signature verification system consisting of software and an information processing terminal in which this verification software is installed,
The verification software includes information reading means for reading out information included in the electronic signature for the purpose of visualization from the electronic signature;
Information expansion means for expanding the read information for visualization and the information visualized in the extracted display area in the storage unit of the information processing terminal;
Comprising information comparing means for comparing the information for visualization that has been read out and expanded in the storage unit of the information processing terminal with the information that is visualized in the extracted display area;
A method for verifying the contents of an electronic signature, wherein the validity of the electronic signature is authenticated only when the comparison result matches. The information comparison means converts the information for the purpose of visualization read out from the electronic signature and developed in the storage unit of the information processing terminal into a data format via a conversion means for converting the information into the format of the information visualized in the display area. And comparing the data newly developed in the storage unit of the information processing terminal with the data developed in the storage unit of the information processing terminal that has extracted the information developed in the display area. Item 2. A method for verifying electronic signature content according to Item 1. The information comparison means extracts information from the display area on the digital data and visualizes the information visualized in the display area developed in the storage unit of the information processing terminal, for the purpose of visualization included in the electronic signature The data is converted via the conversion means for converting to the format of the data, the data developed in the storage unit of the information processing terminal and the information included in the electronic signature for the purpose of visualization are read out, and the storage unit of the information processing terminal 2. The method for verifying the contents of an electronic signature according to claim 1, wherein the data is compared with the data expanded on the electronic signature.

Images