Time stamp issuing system, time stamp issuing method, and time stamp issuing program

Abstract

To enable providing a highly sustainable time stamp service at reduced use cost.SOLUTION: In a time stamp issuing system 1, a time stamp station 10 includes an intra-station time server 12, a time stamp server 13 and a time stamp clock 14. The intra-station time server 12 acquires standard time information from a national time standard organization 3 to synchronize first time information of a first clock 12f of itself, with the standard time information. The time stamp clock 14 indicates time-stamp time information to be used for the generation of a time stamp token 60. The time stamp server 13 synchronizes second time information of a second clock 13f of itself, with the first time information, and synchronizes the time-stamp time information of the time stamp clock 14, with the second time information, so as to generate the time stamp token 60 based on a hash value 61 of an electronic file 50 and the time-stamp time information.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a timestamp issuing system, a timestamp issuing method, and a timestamp issuing program that issue a timestamp token for certifying an electronic file. [Background technology]

[0002] Conventionally, a technology has been known in which an original file (electronic file) of electronic data such as a document, image, video, or audio is stamped (applied) with a timestamp to certify the original file. For example, a user wishing to have an original file certified calculates a hash value of the original file using a hash algorithm on their own computer or the like, and sends the hash value to a timestamp authority. The timestamp authority generates data that combines the hash value and information such as the current time, applies a digital signature to this data using a private key, generates a timestamp token, and returns it to the user. The user stamps the original file by adding the timestamp token, which proves that the original file existed at the time added to the timestamp token.

[0003] For example, the timestamp system disclosed in Patent Document 1 below comprises multiple client terminals, a timestamp authority that issues timestamps to these client terminals, a time audit authority that audits the time of the timestamp authorities, and a national time distribution authority that audits the time of the time audit authority, all of which are arranged so that they can be connected via a network. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-072585 Summary of the Invention [Problem to be solved by the invention]

[0005] A time stamp authority (TSA) has a TSA clock and issues time stamps based on the current time indicated by the TSA clock. The time on the TSA clock is set based on time information distributed by a time distribution authority (TAA), such as a time audit authority. The time stamp authority receives time information distributed by the time distribution authority and has its TSA clock audited by the time distribution authority. The time distribution authority has a TAA clock and distributes time information based on the current time indicated by the TAA clock. The time on the TAA clock is set by comparing and synchronizing with Coordinated Universal Time (UTC) managed by a national time standardization agency (NTA), such as the National Institute of Information and Communications Technology (NICT). In other words, the time distribution authority distributes time information to the time stamp authority based on a TAA clock synchronized with UTC, and audits the TSA clock by measuring the time difference between the TSA clock and the TAA clock, thereby ensuring the time traceability of the TSA clock to UTC.

[0006] However, because time distribution stations use specialized equipment and software that is dependent on specific manufacturers, operation and maintenance costs are high, and these costs are added to the user's usage fees for the time distribution station. In addition, if a problem occurs with the specialized equipment or software that is dependent on the manufacturer, it takes time for the operator to recover, and time information cannot be distributed to the time stamp station until the problem is resolved, which means that users cannot use the time stamp service provided by the time stamp station.

[0007] Therefore, in time stamp issuing systems, there is a need for technology that can provide time stamp services without interruption and at a lower usage cost while guaranteeing time traceability to Coordinated Universal Time for the time information from the TSA clock of the time stamp authority that is added to the time stamp.

[0008] In the technology disclosed in Patent Document 1, the TSA evaluates the accuracy of the time distributed from the TAA, and because the accuracy of the time distributed from the TAA depends on the transmission path from the NTA to the TAA to the TSA, the TSA evaluates the accuracy of the time distributed from the TAA by inquiring about the accuracy from the NTA and the TAA, etc. The TSA performs an action according to the evaluation result, for example, determining whether or not to issue a timestamp token.

[0009] However, according to the technology disclosed in Patent Document 1, time stamp tokens are issued using the time distributed by the TAA, so the operation and maintenance costs of the TAA are added to the user's usage fee for the time stamp service. Furthermore, because the TAA uses special equipment, if it stops due to a problem, it takes time to restore the service, and users will not be able to use the time stamp service until it is restored.

[0010] The present invention has been developed in consideration of problems such as those described above, and an object of the present invention is to provide a timestamp issuance system, a timestamp issuance method, and a timestamp issuance program that can provide a highly sustainable timestamp service at a lower usage cost. [Means for solving the problem]

[0011] In order to solve the above problem, a first time stamp issuing system of the present invention is a time stamp issuing system having a time stamp authority that issues a time stamp token to certify an electronic file, wherein the time stamp authority acquires standard time information from a distribution organization that distributes standard time information of standard time, and comprises: an in-station time server having a first clock and synchronizing the first time information indicated by the first clock with the standard time information; a time stamp clock that indicates time stamp time information used to generate the time stamp token; and a time stamp server having a second clock and synchronizing the second time information indicated by the second clock with the first time information, and generating the time stamp token based on a hash value of the electronic file;The time stamp authority further includes an external time server that acquires satellite time information from a positioning satellite, has a third clock, and synchronizes the third time information indicated by the third clock with the satellite time information, and the time stamp authority further includes a front server that verifies the time stamp time information of the time stamp token generated by the time stamp server; The timestamp server synchronizes the timestamp time information indicated by the timestamp clock with the second time information, and generates the timestamp token based on the hash value and the timestamp time information. The front server receives the third time information from the external time server, has a fourth clock, synchronizes the fourth time information indicated by the fourth clock with the third time information, and determines whether the timestamp time information of the timestamp token is valid using the fourth time information. It is characterized by:

[0012] In order to solve the above problem, a first time stamp issuing method of the present invention is a method for issuing a time stamp token for certifying an electronic file from a time stamp authority, the method comprising the steps of: acquiring standard time information from a distribution organization that distributes standard time information of standard time, by an internal time server of the time stamp authority, and synchronizing first time information indicated by a first clock of the internal time server with the standard time information; indicating time stamp time information to be used for generating the time stamp token, by a time stamp clock of the time stamp authority; and synchronizing second time information indicated by a second clock of the time stamp server with the first time information, by a time stamp server of the time stamp authority, and generating the time stamp token based on a hash value of the electronic file. a step of acquiring satellite time information from a positioning satellite by an external time server, and synchronizing the third time information indicated by the third clock with the satellite time information by a third clock; and a step of verifying the timestamp time information of the timestamp token generated by the timestamp server by a front server provided in the timestamp station; and further comprising: in the timestamp server, synchronizing the timestamp time information indicated by the timestamp clock with the second time information, and generating the timestamp token based on the hash value and the timestamp time information. the front server receives the third time information from the external time server, has a fourth clock, synchronizes the fourth time information indicated by the fourth clock with the third time information, and determines whether the timestamp time information of the timestamp token is valid using the fourth time information. It is characterized by:

[0014] First time stamp issuing system of the present invention and According to the first timestamp issuing method, the timestamp server can inexpensively and accurately secure the timestamp time information to be added to the timestamp token without going through a time distribution authority (TAA) such as a time audit authority. As a result, it is possible to provide a highly sustainable timestamp service at a lower usage cost, and improve the convenience of timestamp users. In addition, the timestamp server can check based on satellite time information from positioning satellites whether the timestamp time information it obtains from the timestamp clock is an invalid time for the timestamp token (i.e., a time that is not synchronized with the specified accuracy with standard time information such as Coordinated Universal Time (UTC) distributed by the national time standard organization).This makes it possible to address the risk of abnormalities occurring in the range from the national time standard organization to the timestamp server, thereby improving the reliability of the timestamp.

[0015] In the second time stamp issuing system of the present invention, the time stamp authority may further include a log server that stores time difference information between the distribution agency and the in-station time server, time difference information between the in-station time server and the time stamp server, and time difference information between the time stamp server and the time stamp clock.

[0016] According to the second time stamp issuing system of the present invention, it is possible to ensure and prove the traceability of the time stamp time information added to the time stamp token, thereby improving the reliability of the time stamp.

[0017] Third time stamp issuing system of the present invention In The time stamp authority may store information on the time difference between the external time server and the front server.

[0018] According to the third time stamp issuing system of the present invention, By storing time difference information between the off-site time server and the front server, it is possible for a third party to prove that no unauthorized time manipulation has occurred on the front server and that it is operating at accurate time.

[0019] In the fourth timestamp issuance system of the present invention, if the time difference between the timestamp time information of the timestamp token and the fourth time information of the fourth clock is outside a specified time difference range, the front server may determine that the timestamp token is invalid and not issue it.

[0020] According to the fourth timestamp issuance system of the present invention, it is possible to prevent timestamp tokens set with invalid times (i.e., times that are not synchronized with a specified accuracy with standard time information such as Coordinated Universal Time (UTC) distributed by national time standards organizations) from being issued to users, thereby improving the reliability of timestamps.

[0021] In the fifth time stamp issuing system of the present invention, the distribution institution is provided with a plurality of institution time servers, and the in-station time server is communicatively connected to each of the institution time servers via a designated optical telephone line, a designated dedicated line, or a designated Internet line, and the standard time information is obtained from any of the plurality of institution time servers.

[0022] According to the fifth timestamp issuing system of the present invention, it is possible to prevent spoofing of communications between a national time standard organization and an in-station time server, and further, it is possible to make line costs cheaper than communications via a telecommunications carrier, and it is also possible to improve communication security, thereby improving the reliability of the timestamp server.

[0023] In the sixth time stamp issuing system of the present invention, the time stamp authority assigns time stamps to the time difference information between the distribution agency and the in-station time server, the time difference information between the in-station time server and the time stamp server, and the time difference information between the time stamp server and the time stamp clock, and assigns time stamps to the operation logs and event logs of the in-station time server and the time stamp server.

[0024] According to the sixth timestamp issuing system of the present invention, the reliability (non-tampering) of each time difference information stored in the log server and each server's operation log and event log can be improved, thereby improving the reliability of the timestamp server and timestamps.

[0025] In the seventh timestamp issuance system of the present invention, if the time difference between the timestamp time information of the timestamp token and the fourth time information of the fourth clock is outside a specified time difference range, the front server determines that the timestamp token is invalid and issues the timestamp token, while excluding the timestamp token from the charges for the timestamp service.

[0026] According to the seventh time stamp issuing system of the present invention, users can stamp electronic files with time stamp tokens that are not charged, thereby improving the convenience of time stamp users.

[0027] In the eighth timestamp issuance system of the present invention, if the time difference between the timestamp time information of the timestamp token and the fourth time information of the fourth clock is outside a predetermined time difference range, the front server determines the timestamp token to be invalid and issues the timestamp token by adding additional information indicating the verification result of the timestamp token.

[0028] According to the eighth timestamp issuing system of the present invention, even if the timestamp time information attached to the timestamp token does not conform to the specified accuracy of the standard time information of the national time standard organization, it is possible to prove that the electronic file has not been tampered with based on the time difference between the timestamp time information and the fourth time information of the front server, thereby improving the convenience for timestamp users.

[0029] In the ninth timestamp issuing system of the present invention, the front server may change at least one of the charging level of the timestamp service of the timestamp token and the stamp mark corresponding to the timestamp token depending on the time difference between the timestamp time information of the timestamp token and the fourth time information of the fourth clock.

[0030] According to the ninth time stamp issuing system of the present invention, even if the time stamp time information attached to the time stamp token does not conform to the specified accuracy for the standard time information of the national timing organization, the level of accuracy of the time stamp time information can be visualized, thereby improving the convenience for time stamp users. [Effects of the Invention]

[0031] According to the present invention, the time stamp issuing system, the time stamp issuing method, and the time stamp issuing program make it possible to provide a highly sustainable time stamp service at a lower usage cost. [Brief explanation of the drawings]

[0032] [Figure 1] 1 is a block diagram showing a configuration of a timestamp issuing system according to an embodiment of the present invention. [Figure 2] 1 is an explanatory diagram illustrating an example of an electronic file in a time stamp issuing system according to an embodiment of the present invention; [Figure 3] 1 is a block diagram showing the configuration of a data center in a time stamp issuing system according to an embodiment of the present invention. [Figure 4] 1 is a block diagram showing a configuration of a time stamp authority in a time stamp issuing system according to an embodiment of the present invention. [Figure 5] 5 is a flowchart showing a time synchronization operation of an in-station time server of the time stamp issuing system according to the embodiment of the present invention. [Figure 6] 10 is a flowchart showing a time synchronization operation of a time stamp server in the time stamp issuing system according to the embodiment of the present invention. [Figure 7] 10 is a flowchart showing the time synchronization operation of the front server of the time stamp issuing system according to the embodiment of the present invention. [Figure 8] 10 is a flowchart showing a timestamp issuing operation of the timestamp issuing system according to the embodiment of the present invention. [Figure 9] 10 is a flowchart illustrating a timestamp token verification operation of a front server of a timestamp issuing system according to an embodiment of the present invention. [Figure 10] 10 is a table showing an example of first time difference information between a national time standard organization and an in-station time server in a time stamp issuing system according to an embodiment of the present invention. [Figure 11] 10 is a table showing an example of second time difference information between an in-station time server and a time stamp server in the time stamp issuing system according to the embodiment of the present invention. [Figure 12] 10 is a table showing an example of third time difference information between a time stamp server and a time stamp clock in the time stamp issuing system according to an embodiment of the present invention. [Figure 13] 10 is a table showing an example of fourth time difference information between an external time server and a front server in a time stamp issuing system according to an embodiment of the present invention. [Figure 14] 10 is a table showing an example of timestamp issuance information of a generated timestamp token in a timestamp issuing system according to an embodiment of the present invention. [Figure 15] 10 is a plan view showing an example of a verification result screen of a timestamp token in a timestamp issuing system according to an embodiment of the present invention. FIG. [Figure 16] 10 is a table showing examples of charge levels and stamp marks for the time stamp service according to the time difference between the time stamp token and the front server in the time stamp issuing system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0033] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments are preferred specific examples of the present invention and disclose various preferred techniques, but the technical scope of the present invention is not limited to these aspects.

[0034] A timestamp issuing system 1 according to an embodiment of the present invention will now be described. As shown in Fig. 1, the timestamp issuing system 1 has a data center 2, which is communicably connected to a National Time Standards Authority (NTA) 3 (distribution organization) and a user terminal 4 via a predetermined network 6, and is also configured to be able to receive positioning signals from positioning satellites 5.

[0035] 2, the timestamp issuing system 1 issues a timestamp token 60 to an electronic file 50 to prove that the electronic data 51 of the electronic file 50 existed at the time of issuance of the timestamp token 60 (proof of existence) and to prove that the electronic data 51 has not been tampered with after the timestamp token 60 was issued (proof of integrity). When the timestamp token 60 is added to the electronic file 50, a stamp mark indicating the addition of the timestamp token 60 is displayed, for example, in the header of the electronic file 50.

[0036] In this embodiment, the electronic file 50 includes electronic data 51 such as documents, images, videos, and audio, and is configured, for example, as a PDF file. To verify the existence or integrity of the electronic data 51, a timestamp token 60 based on a hash value 61 of the electronic data 51 can be added to the electronic file 50, as shown in FIG. 2 . That is, the timestamp token 60 can be embedded in the electronic file 50 to form a single file. The timestamp token 60 includes, for example, the hash value 61, time information 62 indicating the time at which the timestamp token 60 was issued, a digital signature 63 for the hash value 61 and the time information 62, and a digital certificate 64 for verifying the digital signature 63. The digital certificate 64 includes, for example, a public key 65, expiration date information 66, and a signature 67.

[0037] As shown in Figures 1 and 3, the data center 2 has a time stamp authority (TSA) 10 and an off-site time server 11, and the time stamp authority 10 has an on-site time server 12, a time stamp server 13, a time stamp clock 14, a front server 15, a log server 16, and a monitoring server 17.

[0038] 4, the in-station time server 12 has a first clock 12f that indicates first time information, and the timestamp server 13 has a second clock 13f that indicates second time information. The out-station time server 11 has a third clock 11f that indicates third time information, and the front server 15 has a fourth clock 15f that indicates fourth time information. In particular, the timestamp clock 14 is a clock that indicates the timestamp time information added to the timestamp token 60. [National Time Standards Agency]

[0039] The national time standard organization 3 is an organization such as the National Institute of Information and Communications Technology (NICT) that supplies standard time information (standard time information), and is equipped with multiple central time servers 18 that have Coordinated Universal Time (UTC) as time information. Although three central time servers 18 are shown in FIG. 1, the time stamp issuing system 1 may be equipped with one or two central time servers 18 for one national time standard organization 3, or may be equipped with four or more central time servers 18. The multiple central time servers 18 are servers that hold standard time information, and are each connected to an external device (e.g., an in-station time server 12) via a different communication means so that they can communicate with the external device, and supply the standard time information to the external device in response to a request from the external device. [User terminal]

[0040] The user terminal 4 is a device such as a personal computer used by a user who uses the timestamp service (issuance of a TST) to certify the electronic file 50. Although one user terminal 4 is shown in FIG. 1, the timestamp issuing system 1 may have multiple user terminals 4 connected to one data center 2. The user terminal 4 communicates with the data center 2 in response to the user's operation, and causes the data center 2 to issue a timestamp token 60 to be added to the electronic file 50.

[0041] The user terminal 4 includes, for example, a control unit 4a, a storage unit 4b, a communication unit 4c, a display unit 4d, and an input device 4e. The control unit 4a is configured with a computer such as a CPU, and the storage unit 4b is configured with storage media such as a ROM, RAM, and hard disk. The control unit 4a performs arithmetic processing based on the programs and data stored in the storage unit 4b, thereby providing overall control over the various units and functions of the user terminal 4. The user terminal 4 is connected to the timestamp server 13 in the data center 2 via the communication unit 4c and the network 6 so as to be able to communicate with the data center 2.

[0042] For example, the control unit 4a executes a timestamp assignment program stored in the storage unit 4b to operate as the timestamp request unit 20, the hash value calculation unit 21, and the timestamp addition unit 22. In other words, the storage unit 4b stores a timestamp assignment program for causing a computer to function as the user terminal 4 equipped with the timestamp request unit 20, the hash value calculation unit 21, and the timestamp addition unit 22. The timestamp request unit 20, the hash value calculation unit 21, and the timestamp addition unit 22 implement the timestamp request step, the hash value calculation step, and the timestamp addition step of the timestamp issuing method according to the present invention.

[0043] The timestamp assignment program may be started when the user terminal 4 is started, or may be started in response to an operation of the user terminal 4. The timestamp assignment program executes various processes such as a timestamp request, hash value calculation, and timestamp addition in response to an operation by the user.

[0044] The timestamp request unit 20 requests the timestamp server 13 in the data center 2 to issue a timestamp token 60 for authenticating the electronic file 50 specified by the user. For example, the timestamp request unit 20 not only requests the issuance of the timestamp token 60 for the electronic file 50, but also transmits a hash value 61 of the electronic file 50 to the timestamp server 13. Note that the timestamp request unit 20 may specify not only a single electronic file 50 but also multiple electronic files 50 as the target for assigning a timestamp, or may specify a folder containing multiple electronic files 50.

[0045] The hash value calculation unit 21 calculates a hash value 61 using a predetermined hash algorithm for the electronic data 51 of the electronic file 50 for which the timestamp request unit 20 requests the issuance of a timestamp token 60.

[0046] The timestamp addition unit 22 receives the timestamp token 60 sent from the front server 15 in response to the issuance request from the timestamp request unit 20, and adds it to the corresponding electronic file 50, thereby stamping (applying) a timestamp to the electronic file 50. [Positioning satellite]

[0047] Next, the positioning satellite 5 will be described. The positioning satellite 5 is an artificial satellite that transmits a positioning signal required to measure location information. While one positioning satellite 5 is illustrated in FIG. 1, the timestamp issuing system 1 may have multiple positioning satellites 5. The positioning satellite 5 is, for example, the quasi-zenith satellite "Michibiki," which is equipped with a rubidium atomic clock and provides accurate time information with an error of less than one second in 300,000 years. The positioning satellite 5 may also be another GNSS satellite, such as a GPS satellite.

[0048] In a satellite positioning system using positioning satellites 5, the positioning satellites 5 transmit positioning signals including time information at the time of transmission, and a receiver on the ground simultaneously receives the positioning signals from multiple positioning satellites 5. The receiver calculates the position information of the receiver based on the positioning signal from each positioning satellite 5, and also calculates the time information at the receiver's position, thereby obtaining the time information of the positioning satellites 5 (satellite time information). [Off-site time server]

[0049] Next, each part of the data center 2 will be described with reference to Figures 3 and 4. The off-station time server 11 is a server that acquires time information (satellite time information) from the positioning satellite 5 and holds third time information synchronized with the satellite time information, and is communicatively connected to an external device (for example, the front server 15) and distributes the third time information to the external device in response to a request from the external device.

[0050] For example, as shown in Figure 3, the outside time server 11 includes a control unit 11a, a storage unit 11b, a communication unit 11c, a display unit 11d, an input device 11e, and a third clock 11f. The control unit 11a is composed of a computer such as a CPU, and the storage unit 11b is composed of storage media such as a ROM, RAM, and hard disk. The control unit 11a performs calculations based on the programs and data stored in the storage unit 11b, thereby providing overall control of the various units and functions of the outside time server 11. The outside time server 11 is connected to the front server 15 via the communication unit 11c so as to be able to communicate with it.

[0051] For example, control unit 11a executes a time management program stored in storage unit 11b to operate as time synchronization unit 25 and time distribution unit 26. In other words, storage unit 11b stores a time management program for causing a computer to function as external time server 11 equipped with time synchronization unit 25 and time distribution unit 26. The time synchronization unit 25 and time distribution unit 26 implement the time synchronization step and time distribution step of the time stamp issuing method according to the present invention.

[0052] The time synchronizer 25 simultaneously receives positioning signals from multiple positioning satellites 5, calculates the position information of the external time server 11 based on the positioning signals of each positioning satellite 5, and calculates the time information at the position of the external time server 11, thereby acquiring the time information (satellite time information) of the positioning satellites 5. The time synchronizer 25 then periodically acquires satellite time information from the positioning satellites 5, that is, at predetermined time intervals (for example, every 10 minutes), and synchronizes the third time information indicated by the third clock 11f with the acquired satellite time information.

[0053] The time distribution unit 26 receives a time distribution request from the front server 15, and distributes the third time information indicated by the third clock 11f to the front server 15 in response to the time distribution request. [Internal time server]

[0054] The in-station time server 12 is a server that acquires time information (standard time information) from the national time standard organization 3 and holds first time information synchronized with the standard time information. It is communicatively connected to an external device (e.g., a timestamp server 13) and distributes the first time information to the external device in response to a request from the external device.

[0055] For example, as shown in FIG. 4, the local time server 12 includes a control unit 12a, a memory unit 12b, a communication unit 12c, a display unit 12d, an input device 12e, and a first clock 12f. The control unit 12a is configured as a computer such as a CPU, and the memory unit 12b is configured as a storage medium such as a ROM, RAM, and hard disk. The control unit 12a executes calculations based on programs and data stored in the memory unit 12b, thereby controlling the various components and functions of the local time server 12. The local time server 12 is communicatively connected to the national time standard organization 3 and the time stamp server 13 via the communication unit 12c. The local time server 12 is connected to multiple central time servers 18 of the national time standard organization 3 via different communication means, such as an optical fiber line or a dedicated line such as a VPN or Internet VPN. If the risk of spoofing in communication with the central time server 18 is determined to be low, the local time server 12 may be connected to the central time server 18 via an Internet line.

[0056] For example, the control unit 12a executes a time management program stored in the storage unit 12b to operate as the time synchronization unit 30 and the time distribution unit 31. In other words, the storage unit 12b stores a time management program for causing a computer to function as the in-station time server 12 equipped with the time synchronization unit 30 and the time distribution unit 31. The time synchronization unit 30 and the time distribution unit 31 implement the time synchronization step and the time distribution step of the time stamp issuing method according to the present invention.

[0057] The time synchronization unit 30 is communicatively connected to at least one of the multiple institutional time servers 18 of the national time standard organization 3 via the communication unit 12c, and acquires standard time information from the institutional time server 18. If the reliability of communication with one institutional time server 18 cannot be ensured, the time synchronization unit 30 acquires standard time information by communicating with another institutional time server 18. The time synchronization unit 30 then periodically acquires standard time information from the institutional time server 18, i.e., at predetermined time intervals (for example, every 10 minutes), and synchronizes the first time information indicated by the first clock 12f with the acquired standard time information.

[0058] Furthermore, the time synchronizer 30 calculates first time difference information (see FIG. 10) between the standard time information and the first time information indicated by the first clock 12f at predetermined time intervals (for example, every 10 seconds), stores (saves) it in the memory 12b, and transmits it to the log server 16. Note that the time synchronizer 30 may calculate the first time difference information for each of the multiple engine time servers 18 and transmit it to the log server 16.

[0059] The time distribution unit 31 receives a time distribution request from the time stamp server 13, and distributes the first time information indicated by the first clock 12f to the time stamp server 13 in response to the received time distribution request. [Timestamp Server]

[0060] The timestamp server 13 is a server that generates a timestamp token 60 for an electronic file 50 based on the timestamp time information of the timestamp clock 14, and is communicatively connected to an external device (e.g., a user terminal 4) to generate a timestamp token 60 in response to an issuance request from the external device.

[0061] The timestamp server 13 is connected to the timestamp clock 14 and is configured to acquire timestamp information from the timestamp clock 14. The timestamp clock 14 may be provided in a device independent of the timestamp server 13, or may be provided in a hardware device such as a hardware security module mounted on the timestamp server 13.

[0062] For example, as shown in Fig. 4, the timestamp server 13 includes a control unit 13a, a memory unit 13b, a communication unit 13c, a display unit 13d, an input device 13e, and a second clock 13f. The control unit 13a is configured with a computer such as a CPU, and the memory unit 13b is configured with storage media such as a ROM, RAM, and hard disk. The control unit 13a performs arithmetic processing based on the programs and data stored in the memory unit 13b, thereby providing overall control over the various units and functions of the timestamp server 13. The timestamp server 13 is connected to the user terminal 4, the in-station time server 12, and the front server 15 via the communication unit 13c so as to be able to communicate with them.

[0063] The second clock 13f indicates second time information based on the system clock of the timestamp server 13. On the other hand, the timestamp clock 14 indicates timestamp time information based on the hardware clock of a hardware device such as a hardware security module that does not depend on the system clock of the timestamp server 13.

[0064] For example, the control unit 13a operates as the time synchronization unit 35 by executing a time management program stored in the storage unit 13b, and operates as the token generation unit 36 ​​by executing a token generation program stored in the storage unit 13b. In other words, the storage unit 13b stores a time management program for causing a computer to function as the time stamp server 13 equipped with the time synchronization unit 35, and also stores a token generation program for causing a computer to function as the time stamp server 13 equipped with the token generation unit 36. The time synchronization unit 35 and the token generation unit 36 ​​implement the time synchronization step and the token generation step of the time stamp issuing method according to the present invention.

[0065] The time synchronizer 35 periodically receives first time information indicated by the first clock 12f from the in-station time server 12 at predetermined time intervals (e.g., every 10 minutes) and synchronizes the second time information indicated by the second clock 13f with the received first time information. In other words, the second time information indicated by the second clock 13f is synchronized with the first time information of the in-station time server 12, which is synchronized with the standard time information of the national timing organization 3. The time synchronizer 35 also periodically synchronizes the timestamp information indicated by the timestamp clock 14 with the second time information indicated by the second clock 13f at predetermined time intervals (e.g., every 10 minutes). In other words, the timestamp time information indicated by the timestamp clock 14 is synchronized with the second time information of the second clock 13f, which is synchronized with the first time information of the in-station time server 12 (synchronized with the standard time information of the national timing organization 3).

[0066] Furthermore, the time synchronizer 35 calculates second time difference information (see FIG. 11) between the first time information and the second time information indicated by the second clock 13f at predetermined time intervals (for example, 10 seconds), stores (saves) it in the memory 13b, and transmits it to the log server 16. The time synchronizer 35 calculates third time difference information (see FIG. 12) between the second time information and the timestamp time information at predetermined time intervals (for example, 10 seconds), stores (saves) it in the memory 13b, and transmits it to the log server 16.

[0067] The token generation unit 36 ​​receives from the user terminal 4 a request to issue a timestamp token 60 for the electronic file 50 and a hash value 61 of the electronic file 50. In response to the received issuance request, the token generation unit 36 ​​generates a timestamp based on the timestamp time information indicated by the timestamp clock 14, and combines the generated timestamp with the hash value 61 of the electronic file 50 to generate a timestamp token 60. The token generation unit 36 ​​transmits the generated timestamp token 60 to the front server 15.

[0068] The token generating unit 36 ​​may encrypt the combined data, such as the hash value 61 and the timestamp time information, with a predetermined private key to generate a digital signature, and add the digital signature to the timestamp token 60. The timestamp token 60 may also include a digital certificate issued for the public key that pairs with the private key. [Front Server]

[0069] The front server 15 is a server that verifies and issues the timestamp token 60 generated by the timestamp server 13, and is communicatively connected to an external device (e.g., the user terminal 4) to issue the timestamp token 60 to the external device. The front server 15 also acquires third time information from the external time server 11 synchronized with the satellite time information of the positioning satellite 5, holds fourth time information synchronized with the third time information, and verifies the timestamp token 60 based on the fourth time information.

[0070] For example, as shown in Fig. 4, the front server 15 includes a control unit 15a, a storage unit 15b, a communication unit 15c, a display unit 15d, an input device 15e, and a fourth clock 15f. The control unit 15a is configured with a computer such as a CPU, and the storage unit 15b is configured with storage media such as a ROM, RAM, and hard disk. The control unit 15a performs arithmetic processing based on the programs and data stored in the storage unit 15b, thereby controlling the various units and functions of the front server 15. The front server 15 is connected to the user terminal 4, the external time server 11, and the time stamp server 13 via the communication unit 15c so as to be able to communicate with them.

[0071] For example, the control unit 15a operates as the time synchronization unit 40 by executing a time management program stored in the storage unit 15b, and operates as the token issuing unit 41 by executing a token issuance program stored in the storage unit 15b. In other words, the storage unit 15b stores a time management program for causing a computer to function as the front server 15 equipped with the time synchronization unit 40, and also stores a token issuance program for causing a computer to function as the front server 15 equipped with the token issuing unit 41. The time synchronization unit 40 and the token issuing unit 41 implement the time synchronization step and the token issuing step of the time stamp issuing method according to the present invention.

[0072] The time synchronizer 40 periodically receives third time information indicated by the third clock 11f from the external time server 11, i.e., at predetermined time intervals (e.g., every 10 minutes), and synchronizes the fourth time information indicated by the fourth clock 15f with the received third time information. In other words, the fourth time information indicated by the fourth clock 15f is synchronized with the third time information of the external time server 11, which is synchronized with the satellite time information of the positioning satellite 5. The time synchronizer 40 also calculates fourth time difference information (see FIG. 13) between the third time information and the fourth time information indicated by the fourth clock 15f at predetermined time intervals (e.g., every 10 seconds), and stores (saves) this information in the memory 15b and transmits it to the log server 16.

[0073] The token issuing unit 41 receives and verifies the timestamp token 60 from the timestamp server 13, and issues the verified timestamp token 60 to the user terminal 4. To verify the timestamp token 60, the token issuing unit 41 determines whether the timestamp time information added to the timestamp token 60 is valid, based on the fourth time information of the fourth clock 15f.

[0074] For example, the token issuing unit 41 compares the timestamp time information added to the timestamp token 60 with the fourth time information of the fourth clock 15f, and if the time difference between the timestamp time information and the fourth time information is within a predetermined time difference range, for example, if the absolute value of the time difference is less than or equal to a predetermined time threshold (for example, 1 second), the token issuing unit 41 determines the timestamp token 60 to be valid and sends (issues) it to the user terminal 4. On the other hand, if the time difference between the timestamp time information and the fourth time information is outside the predetermined time difference range, for example, if the absolute value of the time difference exceeds the predetermined time threshold, the token issuing unit 41 determines the timestamp token 60 to be invalid and does not issue it.

[0075] The time threshold is set taking into consideration the processing specifications and resource status of the timestamp server 13 and the front server 15, the processing specifications and congestion status of the network devices and lines, etc. The time threshold may be a preset initial value, or may be a value manually set by the operator of the timestamp issuing system 1, for example.

[0076] Furthermore, when the token issuing unit 41 determines that the timestamp token 60 is valid and issues it, it counts the user terminal 4 (e.g., the terminal ID of the user terminal 4) or the user of the user terminal 4 (e.g., the user ID of the user) to which the timestamp token 60 is to be sent as a billable subject for the timestamp service, and sends timestamp issuance information (see FIG. 14) including the billing information to the log server 16. In FIG. 14, 1 indicates that a charge has been made, and 0 indicates that a charge has not been made. [Log Server]

[0077] Log server 16 stores information about the time differences between the clocks installed in the various parts of time stamp issuing system 1, as well as operation logs and event logs performed in the various parts.

[0078] For example, as shown in Fig. 4, the log server 16 includes a control unit 16a, a storage unit 16b, and a communication unit 16c. The control unit 16a is configured with a computer such as a CPU, and the storage unit 16b is configured with storage media such as a ROM, a RAM, and a hard disk. The control unit 16a performs arithmetic processing based on the programs and data stored in the storage unit 16b, thereby controlling the various units and functions of the log server 16. The log server 16 is connected to the in-station time server 12, the timestamp server 13, and the front server 15 via the communication unit 16c so as to be able to communicate with them.

[0079] For example, control unit 16a operates as log management unit 45 by executing a log management program stored in storage unit 16b. In other words, storage unit 16b stores a log management program for causing a computer to function as log server 16 equipped with log management unit 45. Note that log management unit 45 implements the log management step of the timestamp issuing method according to the present invention.

[0080] The log management unit 45 receives, from the in-station time server 12, first time difference information between the standard time information of the national timing organization 3 and the first time information of the first clock 12f of the in-station time server 12, and stores and preserves it in the memory unit 16b. The log management unit 45 receives, from the time stamp server 13, second time difference information between the first time information of the first clock 12f of the in-station time server 12 and the second time information of the second clock 13f of the time stamp server 13, and third time difference information between the second time information and the time stamp time information of the time stamp clock 14, and stores and preserves it in the memory unit 16b. In this way, the log server 16 preserves the first time information, the second time information, and the third time information as evidence of the traceability of time synchronization with the national timing organization 3.

[0081] Furthermore, the log management unit 45 receives from the front server 15 fourth time difference information between the third time information of the third clock 11f of the external time server 11 and the fourth time information of the fourth clock 15f of the front server 15, and stores it in the storage unit 16b. By storing the fourth time difference information, the log server 16 can certify to a third party that no unauthorized time manipulation has been performed on the front server 15 and that the front server 15 is operating at the correct time.

[0082] The log management unit 45 may assign a timestamp to each piece of time difference information, such as the first time difference information, the second time difference information, the third time difference information, and the fourth time difference information, stored in the storage unit 16b. At this time, the log management unit 45, similar to the hash value calculation unit 21 of the user terminal 4, calculates a hash value 61 of the time difference information to which a timestamp is to be assigned, and transmits the calculated hash value 61 to the timestamp server 13 together with a request to issue a timestamp token 60. Then, similar to the timestamp addition unit 22 of the user terminal 4, the log management unit 45 receives the timestamp token 60 sent from the front server 15 in response to the issuance request, and adds it to the corresponding time difference information, thereby stamping (adding) a timestamp to the time difference information.

[0083] The log management unit 45 receives operation logs and event logs performed at each server from the off-station time server 11, the in-station time server 12, the timestamp server 13, the front server 15, and the monitoring server 17, and stores and preserves them in the memory unit 16b. For example, the log management unit 45 receives timestamp issuance information of the timestamp token 60 issued by the timestamp server 13 and the front server 15 from the front server 15, and stores and preserves them in the memory unit 16b.

[0084] The log management unit 45 may assign a timestamp to the operation log or event log stored in the storage unit 16b. In this case, the log management unit 45 calculates a hash value 61 of the operation log or event log to which the timestamp is to be assigned, similar to the hash value calculation unit 21 of the user terminal 4, and transmits the calculated hash value 61 to the timestamp server 13 together with a request to issue a timestamp token 60. Then, similar to the timestamp addition unit 22 of the user terminal 4, the log management unit 45 receives the timestamp token 60 sent from the front server 15 in response to the issuance request, and adds it to the corresponding operation log or event log, thereby stamping (adding) a timestamp to the operation log or event log.

[0085] The monitoring server 17 monitors each piece of time difference information stored in the log server 16. Specifically, the monitoring server 17 monitors whether each piece of time difference information and the total value of each piece of time difference information are within a predetermined value, and if they are outside the predetermined value, notifies the operator of the time stamp issuing system 1 of an abnormality in each piece of time difference information.

[0086] For example, if the sum of the first time difference information between the national time standard organization 3 and the in-station time server 12, the second time difference information between the in-station time server 12 and the timestamp server 13, and the third time difference information between the timestamp server 13 and the timestamp clock 14 is within a predetermined value (e.g., 1 second), the monitoring server 17 determines each time difference information to be normal, and if it exceeds the predetermined value, it determines each time difference information to be abnormal. Furthermore, the monitoring server 17 monitors whether each time difference information, operation log, and event log indicate an abnormal state such as an error log, and if it detects an abnormal state, it notifies the operator of the timestamp issuing system 1 of the log of the abnormal state.

[0087] Next, the operation of the time stamp issuing system 1 of this embodiment will be described with reference to the flowcharts of FIGS.

[0088] First, as a premise, in the time stamp issuing system 1, the clocks of the off-site time server 11, the on-site time server 12, the time stamp server 13, and the front server 15 are synchronized.

[0089] 5, in the in-station time server 12, the time synchronization unit 30 periodically acquires standard time information from the institutional time server 18 (step S1) and synchronizes the first time information of the first clock 12f with the standard time information (step S2). Furthermore, the time synchronization unit 30 calculates first time difference information between the standard time information and the first time information and stores it in the memory unit 12b (step S3).

[0090] 6, in the time stamp server 13, the time synchronization unit 35 periodically acquires first time information from the in-station time server 12 (step S11) and synchronizes the second time information of the second clock 13f with the first time information (step S12). Furthermore, the time synchronization unit 35 calculates second time difference information between the first time information and the second time information and stores it in the storage unit 13b (step S13). Furthermore, the time synchronization unit 35 synchronizes the time stamp information of the time stamp clock 14 with the second time information (step S14). Furthermore, the time synchronization unit 35 calculates third time difference information between the second time information and the time stamp time information and stores it in the storage unit 13b (step S15).

[0091] 7, in the external time server 11, the time synchronization unit 25 periodically acquires satellite time information from the positioning satellites 5 (step S21) and synchronizes the third time information of the third clock 11f with the satellite time information (step S22). In the front server 15, the time synchronization unit 40 periodically acquires the third time information from the external time server 11 (step S23) and synchronizes the fourth time information of the fourth clock 15f with the third time information (step S24). Furthermore, the time synchronization unit 40 calculates fourth time difference information between the third time information and the fourth time information and stores it in the memory unit 15b (step S25).

[0092] 8, when stamping a timestamp on an electronic file 50 in the timestamp issuing system 1, the user first operates the user terminal 4 to specify the electronic file 50 to which the timestamp is to be assigned. The user terminal 4 reads the electronic file 50 and starts the process of assigning a timestamp to the electronic file 50 (step S31). At this time, the hash value calculation unit 21 in the user terminal 4 calculates a hash value 61 for the electronic file 50 (step S32). Next, the timestamp request unit 20 sends the calculated hash value 61 to the timestamp server 13 together with a request to issue a timestamp token 60 for the electronic file 50 (step S33).

[0093] When the timestamp server 13 receives a request to issue a timestamp token 60 and the hash value 61 of the electronic file 50 (step S41), the token generation unit 36 ​​generates a timestamp based on the timestamp time information of the timestamp clock 14 in response to the issuance request, and combines the timestamp with the hash value 61 of the electronic file 50 to generate the timestamp token 60 (step S42). The token generation unit 36 ​​sends the generated timestamp token 60 to the front server 15 (step S43), and proceeds to verify the timestamp token 60 (step S50).

[0094] In the front server 15, as shown in Figure 9, the token issuing unit 41 compares the timestamp time information of the timestamp token 60 with the fourth time information of the fourth clock 15f, and if the time difference between the timestamp time information and the fourth time information is within a predetermined time difference range (step S51: YES), it determines that the timestamp token 60 is valid, counts it as a chargeable item for the timestamp service, generates timestamp issuance information (step S52), and sends it to the user terminal 4 (step S53).

[0095] On the other hand, if the time difference between the timestamp time information and the fourth time information is outside the specified time difference range (step S51: NO), the token issuing unit 41 determines that the timestamp token 60 is invalid, excludes it from the billing target for the timestamp service, does not count it as a billing target, generates timestamp issuance information (step S54), and does not send it to the user terminal 4 (step S55).

[0096] When the timestamp token 60 is issued, the user terminal 4 receives the timestamp token 60 (step S34), and the timestamp addition unit 22 stamps (adds) a timestamp to the electronic file 50 by adding the timestamp token 60 to the corresponding electronic file 50 (step S35).

[0097] In the above embodiment, an example of a configuration in which the in-station time server 12 and the in-station time server 13 of the time stamp authority 10 are provided separately has been described, but the present invention is not limited to this example. In another example, the time stamp server 13 may be configured to have the functions of the in-station time server 12.

[0098] In the above embodiment, an example of a configuration in which the time stamp issuing system 1 has the time stamp server 13 of the time stamp authority 10 and the front server 15 as separate entities has been described, but the present invention is not limited to this example. In another example, the time stamp server 13 may be configured to have the functions of the front server 15.

[0099] As described above, according to this embodiment, the timestamp issuing system 1 is a system having a timestamp authority 10 that issues a timestamp token 60 for certifying an electronic file 50. The timestamp authority 10 includes an internal time server 12, a timestamp server 13, and a timestamp clock 14. The internal time server 12 acquires standard time information from a national timing organization 3 (a distribution organization) that distributes standard time information of standard time. The internal time server 12 includes a first clock 12f and synchronizes the first time information indicated by the first clock 12f with the standard time information. The timestamp clock 14 indicates timestamp time information used to generate the timestamp token 60. The timestamp server 13 includes a second clock 13f and synchronizes the second time information indicated by the second clock 13f with the first time information, and generates the timestamp token 60 based on a hash value 61 of the electronic file 50. The timestamp server 13 also synchronizes the timestamp time information indicated by the timestamp clock 14 with the second time information, and generates the timestamp token 60 based on the hash value 61 and the timestamp time information.

[0100] With this configuration, in the timestamp issuing system 1 according to this embodiment, the timestamp server 13 can inexpensively and accurately secure the timestamp time information to be added to the timestamp token 60 without going through a time distribution authority (TAA) such as a time audit authority. This makes it possible to provide a highly sustainable timestamp service at a lower usage cost, improving the convenience of timestamp users.

[0101] In addition, in this embodiment, in the time stamp issuing system 1, the time stamp authority 10 further includes a log server 16 that stores first time difference information between the national time standard organization 3 and the in-office time server 12, second time difference information between the in-office time server 12 and the time stamp server 13, and third time difference information between the time stamp server 13 and the time stamp clock 14.

[0102] With this configuration, it is possible to ensure and prove the traceability of the timestamp time information added to the timestamp token 60, thereby improving the reliability of the timestamp.

[0103] In this embodiment, the time stamp issuing system 1 further includes an external time server 11 that acquires satellite time information from a positioning satellite 5, has a third clock 11f, and synchronizes the third time information indicated by the third clock 11f with the satellite time information. The time stamp authority 10 further includes a front server 15 that verifies the time stamp information of the time stamp token 60 generated by the time stamp server 13. The front server 15 receives the third time information from the external time server 11, has a fourth clock 15f, synchronizes the fourth time information indicated by the fourth clock 15f with the third time information, and uses the fourth time information to determine whether the time stamp information of the time stamp token 60 is valid. The time stamp authority 10 stores fourth time difference information between the external time server 11 and the front server 15.

[0104] With this configuration, it is possible to check, based on the satellite time information from the positioning satellite 5, whether the timestamp time information that the timestamp server 13 obtains from the timestamp clock 14 is an invalid time in the timestamp token 60 (i.e., a time that is not synchronized with the specified accuracy with standard time information such as Coordinated Universal Time (UTC) distributed by the national time standard organization 3).This makes it possible to prevent the risk of abnormalities occurring in the area from the national time standard organization 3 to the timestamp server 13, thereby improving the reliability of the timestamp.

[0105] Furthermore, in this embodiment, in the timestamp issuance system 1, if the time difference between the timestamp time information of the timestamp token 60 and the fourth time information of the fourth clock 15f is outside a specified time difference range, the front server 15 determines that the timestamp token 60 is invalid and does not issue it.

[0106] This configuration makes it possible to prevent a timestamp token 60 set with an invalid time (i.e., a time that is not synchronized with a specified accuracy with standard time information such as Coordinated Universal Time (UTC) distributed by the national time standard organization 3) from being issued to a user, thereby improving the reliability of the timestamp.

[0107] In addition, in this embodiment, in the time stamp issuing system 1, the national time standard organization 3 has multiple organization time servers 18, and the in-station time server 12 is communicatively connected to each organization time server 18 via a specified optical telephone line, a specified dedicated line, or an Internet line, and obtains standard time information from any of the multiple organization time servers 18.

[0108] This configuration makes it possible to prevent spoofing of communications between the national time standard organization 3 and the in-station time server 12, and furthermore makes it possible to reduce line costs compared to communications via a telecommunications carrier, and also improves communication security, thereby improving the reliability of the timestamp server 13.

[0109] Furthermore, in this embodiment, in the time stamp issuing system 1, the time stamp authority 10 assigns a time stamp to the first time difference information between the national time standard organization 3 and the in-station time server 12, the second time difference information between the in-station time server 12 and the time stamp server 13, and the third time difference information between the time stamp server 13 and the time stamp clock 14, and assigns a time stamp to the operation log and event log of the in-station time server 12 and the time stamp server 13.

[0110] This configuration improves the reliability (non-tampering) of the time difference information stored in the log server 16 and the operation logs and event logs of each server, thereby improving the reliability of the timestamp server 13 and the timestamps.

[0111] In the above embodiment, an example was described in which, in the timestamp issuance system 1, if the time difference between the timestamp time information of the timestamp token 60 and the fourth time information of the fourth clock 15f is outside a specified time difference range, the front server 15 determines the timestamp token 60 to be invalid and does not issue it, but the present invention is not limited to this example.

[0112] For example, in another embodiment, if the time difference between the timestamp time information and the fourth time information is outside a predetermined time difference range, the front server 15 may determine that the timestamp token 60 is invalid, and may add additional information indicating the verification result of the timestamp token 60 to the timestamp token 60 and issue the timestamp token 60. The front server 15 may add, for example, the time difference between the timestamp time information and the fourth time information as additional information. This makes it possible to prove that the electronic file 50 has not been tampered with based on the time difference between the timestamp time information and the fourth time information of the front server 15, even if the timestamp time information added to the timestamp token 60 does not conform to the predetermined accuracy of the standard time information of the national time standard organization 3, thereby improving the convenience of timestamp users.

[0113] In another embodiment, if the time difference between the timestamp time information and the fourth time information is outside a predetermined time difference range, the front server 15 determines that the timestamp token 60 is invalid and issues the timestamp token 60, but may exclude the timestamp token 60 from the charges for the timestamp service, or may generate timestamp issuance information without counting it as a chargeable item. This allows the user to stamp a timestamp on the electronic file 50 using the timestamp token 60 for which no charges are incurred, thereby improving the convenience of timestamp users.

[0114] In another embodiment, if the time difference between the timestamp time information and the fourth time information is outside a specified time difference range, the front server 15 may determine that the timestamp token 60 is invalid, and when issuing the timestamp token 60 with additional information indicating the verification result of the timestamp token 60 added to the timestamp token 60, may display a verification result screen (see Figure 15) showing the verification result of the timestamp token 60 on the user terminal 4.

[0115] In another embodiment, the front server 15 may change at least one of the charge level for the timestamp service of the timestamp token 60 and the stamp mark corresponding to the timestamp token 60, depending on the time difference between the timestamp time information and the fourth time information. This makes it possible to visualize the level of accuracy of the timestamp time information even if the timestamp time information added to the timestamp token 60 does not conform to the predetermined accuracy for the standard time information of the national time standard organization 3, thereby improving the convenience for timestamp users.

[0116] For example, if the time difference between the timestamp time information and the fourth time information is within a predetermined time difference range (for example, if the time difference is within ±1.0 seconds), the front server 15 sets the charging level to the standard level and the charge amount for the timestamp service to the normal fee. Also, if the time difference between the timestamp time information and the fourth time information is outside the predetermined time difference range, the front server 15 lowers the charging level from the standard level and reduces the charge amount for the timestamp service from the normal fee as the time difference deviates from the time difference range. For example, as shown in FIG. 16, the front server 15 reduces the charge amount by 20% if the time difference is greater than ±1.0 seconds but within ±1.2 seconds, by 40% if the time difference is greater than ±1.2 seconds but within ±1.4 seconds, by 60% if the time difference is greater than ±1.4 seconds but within ±1.6 seconds, by 80% if the time difference is greater than ±1.6 seconds but within ±1.8 seconds, and by 100% if the time difference is greater than ±1.8 seconds.

[0117] Furthermore, the front server 15 sets the type of stamp mark to be displayed on the electronic file 50 according to the time difference between the timestamp time information and the fourth time information, and transmits this to the user terminal 4 in addition to the additional information of the timestamp token 60. In the user terminal 4, when the timestamp adding unit 22 adds the timestamp token 60 to the electronic file 50, it writes the type of stamp mark indicated in the additional information of the timestamp token 60 in the header of the electronic file 50 or the like.

[0118] For example, if the time difference between the timestamp time information and the fourth time information is within a predetermined time difference range, the front server 15 sets a stamp mark (e.g., a check mark) of a type indicating the validity of the timestamp token 60. Also, if the time difference between the timestamp time information and the fourth time information is outside the predetermined time difference range, the front server 15 sets a stamp mark (e.g., an exclamation mark) of a type indicating the invalidity of the timestamp token 60. For example, as shown in FIG. 16 , the front server 15 increases the density of the exclamation mark indicating the invalidity of the timestamp token 60 as the time difference becomes smaller, and decreases the density of the exclamation mark indicating the invalidity of the timestamp token 60 as the time difference becomes larger.

[0119] Furthermore, the present invention can be modified as appropriate within the scope that does not contradict the gist or idea of ​​the invention that can be read from the claims and the entire specification, and the timestamp issuance system, timestamp issuance method, and timestamp issuance program that involve such modifications are also included in the technical idea of ​​the present invention. [Industrial Applicability]

[0120] The present invention can be used for managing and operating digitized documents related to intellectual property, tax, medical, and the like. [Explanation of symbols]

[0121] 1. Time stamp issuing system 2 Data Centers 3 National Time Standards Organization (Distribution Organization) 4. User terminal 5. Positioning satellites 6 Network 10 Time Stamp Authority 11 External time server 11th floor 3rd clock 12 Station time server 12th floor 1st clock 13 Timestamp Server 13F 2nd Clock 14 Time Stamp Clock 15 Front Server 15th floor 4th clock 16 Log Server 18 Institutional Time Server 20 Timestamp request part 21 Hash value calculation unit 22 Time stamp addition section 25 Time Synchronization Unit 26 Time Distribution Unit 30 Time Synchronization Unit 31 Time Distribution Unit 35 Time synchronization unit 36 Token Generation Unit 40 Time synchronization unit 41 Token Issuance Department 45 Log Management Department

Claims

1. A time stamp issuing system having a time stamp authority that issues time stamp tokens for authenticating electronic files, the time stamp authority acquires standard time information from a distribution organization that distributes standard time information of standard time, and has a first clock, and an in-station time server that synchronizes the first time information indicated by the first clock with the standard time information; a timestamp clock indicating timestamp information used to generate the timestamp token; a timestamp server having a second clock, synchronizing second time information indicated by the second clock with the first time information, and generating the timestamp token based on a hash value of the electronic file; Equipped with an external time server that acquires satellite time information from a positioning satellite, has a third clock, and synchronizes the third time information indicated by the third clock with the satellite time information; the time stamp authority further comprises a front server that verifies the time stamp information of the time stamp token generated by the time stamp server; the timestamp server synchronizes the timestamp time information indicated by the timestamp clock with the second time information, and generates the timestamp token based on the hash value and the timestamp time information; A timestamp issuing system characterized in that the front server receives the third time information from the external time server, has a fourth clock, synchronizes the fourth time information indicated by the fourth clock with the third time information, and uses the fourth time information to determine whether the timestamp time information of the timestamp token is valid.

2. The time stamp issuing system described in claim 1, characterized in that the time stamp authority further comprises a log server that stores time difference information between the distribution agency and the in-house time server, time difference information between the in-house time server and the time stamp server, and time difference information between the time stamp server and the time stamp clock.

3. 2. The time stamp issuing system according to claim 1, wherein the time stamp authority stores time difference information between the external time server and the front server.

4. The timestamp issuance system described in claim 1, characterized in that if the time difference between the timestamp time information of the timestamp token and the fourth time information of the fourth clock is outside a predetermined time difference range, the front server determines the timestamp token to be invalid and does not issue it.

5. the distribution organization includes a plurality of organization time servers; The time stamp issuing system described in any one of claims 1 to 4, characterized in that the in-house time server is communicatively connected to each of the institutional time servers via a designated optical telephone line, a designated dedicated line, or an Internet line, and obtains the standard time information from any of the multiple institutional time servers.

6. The time stamp issuing system described in any one of claims 1 to 5, characterized in that the time stamp authority assigns time stamps to the time difference information between the distribution agency and the in-station time server, the time difference information between the in-station time server and the time stamp server, and the time difference information between the time stamp server and the time stamp clock, and assigns time stamps to the operation logs and event logs of the in-station time server and the time stamp server.

7. The time stamp issuance system described in claim 1, characterized in that if the time difference between the time stamp time information of the time stamp token and the fourth time information of the fourth clock is outside a specified time difference range, the front server determines the time stamp token to be invalid, issues the time stamp token, and excludes the time stamp token from being charged for the time stamp service.

8. The timestamp issuance system described in claim 1, characterized in that if the time difference between the timestamp time information of the timestamp token and the fourth time information of the fourth clock is outside a predetermined time difference range, the front server determines the timestamp token to be invalid and issues the timestamp token by adding additional information indicating the verification result of the timestamp token.

9. The timestamp issuing system described in claim 1, characterized in that the front server changes at least one of the charging level of the timestamp service of the timestamp token and the stamp mark corresponding to the timestamp token depending on the time difference between the timestamp time information of the timestamp token and the fourth time information of the fourth clock.

10. A time stamp issuing method for issuing a time stamp token for certifying an electronic file from a time stamp authority, comprising: a step of acquiring standard time information from a distribution organization that distributes standard time information of standard time by an in-station time server provided in the time stamp station, and synchronizing first time information indicated by a first clock of the in-station time server with the standard time information; indicating, by a timestamp clock at the timestamp authority, timestamp information used to generate the timestamp token; a step of synchronizing second time information indicated by a second clock of the time stamp server with the first time information by a time stamp server provided in the time stamp authority, and generating the time stamp token based on a hash value of the electronic file; a step of acquiring satellite time information from a positioning satellite by an external time server, and synchronizing third time information indicated by a third clock with the satellite time information; and verifying, by a front server provided in the time stamp authority, the time stamp information of the time stamp token generated by the time stamp server; Furthermore, in the timestamp server, the timestamp time information indicated by the timestamp clock is synchronized with the second time information, and the timestamp token is generated based on the hash value and the timestamp time information; A timestamp issuing method characterized in that the front server receives the third time information from the external time server, has a fourth clock, synchronizes the fourth time information indicated by the fourth clock with the third time information, and uses the fourth time information to determine whether the timestamp time information of the timestamp token is valid.

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