JP4125975B2 - Time stamp system and program thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a time stamp system and a program thereof, and more particularly to a time stamp system and a program thereof capable of verifying a time operation history.
[0002]
[Prior art]
In order to guarantee the existence and non-tampering of electronic documents such as text documents, image information, computer programs, etc. at a certain time, the time information and authentication in the electronic document or its message digest (for example, the hash value of the electronic document) A time stamp system that issues a time stamp certificate generated by encrypting and encrypting a user's signature information is used. In such a time stamp system, a time used for the time stamp system is acquired from a time generator and stamped on an electronic document (see, for example, Patent Document 1).
[0003]
In a computer system such as a time stamp system, various tasks are controlled based on the system time recorded by the clock in the system. However, the accuracy of time generators used in general-purpose personal computers (PCs) is inferior compared to external time sources. If the system time of a time stamp system executed on a general-purpose PC is greatly different from the actual accurate time, an incorrect time is recorded, which is inconvenient for the time stamp system. For this reason, there is a system in which an external engine equipped with a high-accuracy time source synchronizes a clock in the system with a high-accuracy time and the external engine authenticates it (see, for example, Patent Document 2). In this method, a history file indicating that the high-accuracy time acquired from the time source of the external organization has been applied to the local system is sent to an external electronic signature organization, and signature authentication is performed.
[0004]
[Patent Document 1]
Japanese Patent No. 3278721 gazette
[Patent Document 2]
JP-A-2002-229869 [0006]
[Problems to be solved by the invention]
However, in Patent Document 2, a dedicated network resource is required to send a history file to an external electronic signature organization, and the non-falsification of the time operation history stored in the own system cannot be proved. There may be a problem in terms of cost and safety.
[0007]
SUMMARY OF THE INVENTION An object of the present invention is to provide a low-cost and high-security time stamp system that can independently verify a time operation history and a program therefor.
[0008]
[Means for Solving the Problems]
The time stamp system of the present invention is a time stamp system that issues a time stamp certificate in response to a request from a client terminal, and includes a time generation unit that generates a system time and an external time source that acquires an external time from an external time source. A time acquisition unit, and a time correction unit that corrects the system time generated by the time generation unit based on the external time acquired by the external time acquisition unit for each first period and synchronizes with the external time; A history generation unit that generates a history of time correction by the time correction unit as a history file, a certificate generation unit that generates a first time stamp certificate of the history file every second period, and the first time stamp certificate A second time stamp certificate for all records in the database. It generates, characterized in that it comprises a public portion to expose the second time stamp certificate.
[0009]
The database adds the record every time the first time stamp certificate is generated. Each record stores a record hash value and a cumulative hash value, which are hash values of the contents of the record. The cumulative hash value is a hash value for a value obtained by combining the record hash value of the record and the cumulative hash value of the record immediately before the record. The second hash value is obtained by applying an electronic signature to the cumulative hash value. It is preferable to generate a time stamp certificate.
[0010]
The database adds a third time stamp as the record each time a third time stamp certificate is issued to the client terminal, and the certificate generation unit adds a third time stamp certificate to the client terminal. it is also preferred to include a cumulative meter hash value of the previous record to the content of the third time stamp certificate when issuing.
[0011]
Further, the time stamp system program of the present invention, generates a system time a time stamp system program allowed to realize the processing for the time stamp certificate in response to a request from the client terminal on the computer, the time generator The time generation unit based on the external time acquisition process that causes the external time acquisition unit to acquire the external time from the external time source, and the external time acquired for each first period by the external time acquisition process. The time correction process for correcting the system time generated by the system to synchronize with the external time, the history generation process for causing the history generation unit to record the history of the time correction by the time correction process in the history file , and the certificate generation unit allowed to generate a first time stamp certificate of the history file every two periods certificate generation process Characterized comprising: a process allowed to store in the database the first time stamp certificate as one record, and a process allowed to generate a second time stamp certificate for all records in the database to the certificate generation unit .
[0012]
In addition, the process of storing in the database is to add the record every time it is generated, and each record stores a record hash value and a cumulative hash value which are hash values of the contents of the record, and the cumulative total The hash value is a process of setting a hash value for a value obtained by combining the record hash value of the record and the cumulative hash value of the record immediately before the record, and the process of generating the second time stamp certificate It is preferable to provide a process for generating an electronic signature on the hash value to generate the second time stamp certificate.
[0013]
The certificate generation unit includes a process of generating a third time stamp certificate issued in response to a request from the client terminal, and the process of storing in the database includes the generation of the third time stamp certificate. the contents of the third timestamp to each a process of adding to the database as the record, the third process allowed to generate a time stamp certificate, the cumulative meter hash value of the previous record in the third time stamp certificate It is also preferable that the time stamp system program includes a process included in the time stamp.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a time stamp system according to an embodiment of the present invention. The time server 1 as an external time source has a highly accurate time generating unit (not shown), generates a highly accurate and reliable time, and is connected to the time stamp system 3 by a LAN 2. The time server 1 may include a standard time information acquisition device such as a telephone JJY or a long wave standard radio wave, and may synchronize the time of the own system with the standard time.
[0015]
The time stamp system 3 is realized by executing a time stamp system program on a general-purpose PC server. When the constituent elements are shown in a block form, a time generating unit 31, an external time capturing unit 32, and a time correcting unit 33 are shown. And a history generation unit 34, a certificate generation unit 35, a signature key storage unit 36, a database 37, and a disclosure unit 38.
[0016]
The time generation unit 31 generates an internal time of the time stamp system 3 (hereinafter referred to as system time), and is the above-described time generation program of the OS of the general-purpose PC server.
[0017]
The external time acquisition unit 32 makes a time inquiry to the time server 1 at a predetermined interval, for example, an hour interval, using a time inquiry protocol via the network defined by RFC2030, and external time (hereinafter, external time). Say).
[0018]
The time adjustment unit 33 synchronizes the system time generated by the time generation unit 31 with the external time obtained by the external time acquisition unit 32, and passes the external time information to the time correction program of the OS to correct the time. Is. Depending on the OS, the time correction unit 33 may have a function of accessing a time source, and the external time capturing unit 32 may be integrated with the time correction unit 33. Further, the time correction unit 33 passes the correction value to the time correction function to the time correction program. That is, the system time is updated by a predetermined value at a predetermined interval timer interval, and a correction value is added to the predetermined value to correct the time progress. The correction value is obtained, for example, by calculating the difference per interval timer interval from the difference between the external time and the system time at the time inquiry performed at a predetermined interval. By such time synchronization and correction, the system time is maintained with high accuracy. For example, in a Microsoft OS, Windows 2000 environment, fine adjustment in the ns order can be performed by using an OS standard time adjustment function (time correction program). Usually, when synchronization and correction are not performed, the progress error of the time generation unit 31 is about several seconds per day. However, according to synchronization and correction, the time progress between the system time and the external time is typical. The difference is reduced to about 10 ms per day.
[0019]
The history generation unit 34 stores the communication log with the time server 1 and the time reflection information to the own system, for example, the history of the external time for each time correction, the system time, their difference, correction value, etc. in one history file 34a. To record.
[0020]
The certificate generation unit 35 receives a certificate request for requesting issuance of a time stamp certificate for an electronic document from the client terminal 4, and obtains a one-way function (hash function) of the electronic document attached to the certificate request. The content of the time stamp certificate is generated by adding the system time acquired from the time generation unit 31 to the value (hash value) encoded by the action, and the signature key stored in the signature key storage unit 36 is used for the content. Then, encryption is performed to generate an electronic signature, and the electronic signature is attached to the content of the time stamp certificate and issued to the client terminal 4 as a time stamp certificate. Furthermore, the accumulated hash value of the database 37 to be described later may be included in the contents of the time stamp certificate.
[0021]
Further, the certificate generation unit 35 generates the time stamp certificate of the history file 34a at a predetermined interval, for example, the certificate generation unit 35 at a predetermined interval, for example, one day interval. For example, a hash value of the history file 34 a is generated, and the contents of the time stamp certificate are generated by adding the system time acquired from the time generation unit 31 to the hash value, and the content is stored in the signature key storage unit 36. An electronic signature is generated by performing encryption using the signed key, and is attached to the contents of the time stamp certificate as a time stamp certificate. Further, the certificate generation unit 35 inserts the history certificate as one record of the certificate table of the database 37, and, as will be described later, a predetermined interval, for example, an interval of 3 days, the time for the entire certificate table of the database 37. A stamp certificate is generated, that is, a time stamp certificate is generated by applying an electronic signature to a cumulative hash value, which will be described later, and is made public via the publishing unit 38 by WEB, e-mail, or the like. For example, the disclosure unit 38 includes a processing program that uploads a time stamp certificate for the entire certificate table of the database 37 to a predetermined WEB server (not shown) or transmits an e-mail to a predetermined mailing list.
[0022]
The certificate table of the database 37 has, for example, the first record 1 to the nth record n (n is an integer of 2 or more) as shown in FIG. The hash value Hn of the record is stored at the rear of the record n, and the cumulative hash value tbHn is stored at the end of the record n. The cumulative hash value tbHn is obtained as follows.
tbHn = Hash (Hn + tbHn-1)
That is, the cumulative hash value tbH is a hash value obtained for the sum of the hash value of the nth record and the cumulative hash value up to the (n-1) th record. In the case of the first record, since no previous record exists, a random value or a fixed value is substituted for tbH0 corresponding to tbHn-1. According to the cumulative hash value tbH, the record generation order is fixed, and the record cannot be changed afterwards. By issuing such a time stamp certificate of the database 37, it is possible to verify the non-falsification of the history file 34a, and as a result, it is proved that the system time is being operated to maintain high accuracy.
[0023]
Next, the operation of this example will be described with reference to the flowchart of FIG. The time stamp system 3 uses the external time capturing unit 32 to connect to the time server 1 via a prescribed connection procedure, and captures a highly accurate time generated by a time generating unit (not shown) of the time server 1. . The time correction unit 33 corrects the system time using the acquired external time, and simultaneously describes the communication log with the time server 1 and the time reflection information to the own system in the history file 34a (step a).
[0024]
Next, the process of step a is repeated at regular intervals to synchronize the time of the time stamp system 3 with the external time with sufficient accuracy. The history file 34a is encoded using a one-way function (hash function) every period sufficiently longer than the synchronization period to the external time (for example, once a day), and the certificate generation unit 35 is used using the signature key. The electronic signature is performed to generate a time stamp certificate (step b).
[0025]
Next, the data of the time stamp certificate that has been digitally signed in step b is inserted into the database 37 as a record, and the hash value of the time stamp certificate is added to the hash value of the time stamp certificate of the previous record. A cumulative hash is generated and stored in the database 37 (step c).
[0026]
The processes of steps a and c are repeated at regular intervals, and in the meantime, upon receiving a request for issuing a time stamp certificate from the client terminal 4, the time stamp system 3 issues a time stamp certificate and stores it in the database 37. Add a record and update the cumulative hash value of the certificate hash value on the certificate table. Further, the time stamp system 3 generates a time stamp certificate for the database 37 in response to a request from the client terminal 4 or at regular intervals. A cumulative hash value of the database 37 is disclosed by generating it as a table hash certificate in 509 format and posting it on the WEB, sending an e-mail, etc. via the disclosure unit 38 (step d). Since the cumulative hash value of the database 37 becomes publicly known and cannot be changed afterwards, all the records in the table described in the time stamp certificate for the database 37 cannot be changed afterwards (cannot be tampered with). )
The content described in the history file by the above processing is strongly protected by a time stamp certificate that cannot be modified. As a result, it is possible to verify non-falsification of the time operation history such as correction of the system time described in the history file independently without requiring an external certificate authority.
[0027]
【The invention's effect】
According to the present invention, it is possible to verify that the time stamp system is operated at the correct time by using resources available in the system, and it is possible to construct a time stamp system having high reliability at low cost.
[0028]
In particular, a database record that generates a time stamp certificate for a time operation history file such as time correction with high-accuracy time acquired from an external time source or correction for maintaining accuracy, and stores the issuance history of the time stamp certificate Stored as one of them, encoded with a hash value for each record, and a cumulative hash value, which is a cumulative hash value of each record, is calculated and stored each time a record is added. By publishing the time stamp certificate including the value, the certificate issuing history of the time stamp system cannot be tampered with, and the time operation history file cannot be tampered with. In other words, since it is possible to verify the authenticity of the database in units of records generated in the meantime with a certificate that has been published regularly, even if part of the data has been tampered with, the tampered part can be identified as much as possible, Verification with high accuracy is possible. As a result, it is not necessary to send the time adaptation history log file to the external certificate authority as seen in the prior art.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a time stamp system according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram for explaining a database of a time stamp system according to an embodiment of the present invention.
FIG. 3 is a flowchart for explaining the operation of the time stamp system according to the embodiment of the present invention.
[Explanation of symbols]
1 External time source (time server)
3 Time Stamp System 31 Time Generation Unit, Time Generation Processing 32 External Time Acquisition Unit, External Time Acquisition Processing 33 Time Correction Unit, Time Correction Processing 34 History Generation Unit, History Generation Processing 34a History File 35 Certificate Generation Unit, Proof Document generation process 37 Database 4 Client terminal

Claims (6)

A time stamp system that issues a time stamp certificate in response to a request from a client terminal,
A time generator for generating system time;
An external time capturing unit that captures external time from an external time source;
A time correction unit that corrects the system time generated by the time generation unit and synchronizes with the external time based on the external time acquired by the external time acquisition unit for each first period;
A history generation unit for generating a history of time correction by the time correction unit as a history file;
A certificate generation unit for generating a first time stamp certificate of the history file every second period;
A database that stores the first time stamp certificate as one record, and generates a second time stamp certificate for all records in the database, and publishes the second time stamp certificate. A time stamp system comprising: Said database is to add the record for each generation of said first time stamp certificates, each record contains the record hash value and the cumulative hash value is a hash value of the contents of the record Yes, the cumulative hash value is a hash value for a value obtained by combining the record hash value of the record and the cumulative hash value of the record immediately before the record,
The time stamp system according to claim 1, wherein the second time stamp certificate is generated by applying an electronic signature to the cumulative hash value. The database adds a third time stamp as the record every time a third time stamp certificate is issued to the client terminal .
The certificate generation unit to claim 2, characterized in that included in the contents accumulated meter hash value of the previous record in the third time stamp certificate when issuing the third time stamp certificate to said client terminal The described time stamp system. A time stamp system program allowed to realize the processing for the time stamp certificate in response to a request from the client terminal on the computer,
Time generation processing for causing the time generation unit to generate the system time; and
An external time acquisition process for causing the external time acquisition unit to acquire an external time from an external time source; and
A time correction process for correcting the system time generated by the time generation unit based on the external time captured for each first period by the external time acquisition process and synchronizing with the external time;
A history generation process for causing the history generation unit to record a history of time correction by the time correction process in a history file;
A certificate generation process for causing the certificate generation unit to generate a first time stamp certificate of the history file for each second period;
Storing the first time stamp certificate in the database as one record;
Timestamp system program characterized by comprising a process allowed to generate a second time stamp certificate for all records in the database to the certificate generation unit. The process of storing in the database is to add the record every time the first time stamp certificate is generated, and each record includes a record hash value and a cumulative hash value that are hash values of the contents of the record. The accumulated hash value is a process of setting a hash value for a value obtained by combining the record hash value of the record and the accumulated hash value of the record immediately before the record,
The second time stamp certificate process allowed to generate the time stamp system according to claim 4, characterized in that by applying an electronic signature to the cumulative hash value is a process of generating the second time stamp certificate program. A process for causing the certificate generation unit to generate a third time stamp certificate issued in response to a request from the client terminal ;
Processing allowed to store in the database is a process of adding a third time stamp for each generation of the third time stamp certificate in the database as the record,
The third process allowed to generate a time stamp certificate, the time stamp according to cumulative meter hash value immediately before the record to claim 5, characterized in that the process of including the contents of the third time stamp certificate System program.

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