JP6836410B2 - Timestamp server, verification device, timestamp expiration extension program, and verification program - Google Patents

Description

The present invention relates to a time stamp server, a verification device, a time stamp expiration date extension program, and a verification program, and relates to a time stamp extension program.

The time stamp is a digital signature obtained by adding the current time to the hash value of the target electronic data and digitally signing it with the private key of the time stamp server, and in the form of TST (time stamp token) to which various information is added. Issued and provided.
The non-tampering property of electronic data can be confirmed by verifying TST with a public key that forms a key pair with the private key.

By the way, TST has an expiration date due to the guarantee period of the private key.
Therefore, in order to store and store electronic data that requires proof of non-tampering for longer than its expiration date, it is necessary to extend it before the expiration date of TST expires.
Therefore, in the technique of Patent Document 1, the expiration date is extended by collecting data (TSA certificate, CRL, etc.) indicating the validity of TST and reacquiring a time stamp for these data.

However, in this method, work such as timing management of reacquisition, selection of electronic data to be extended, and collection of information necessary for extension must be performed for each electronic data, and some units are 10,000 units. There is also a company that manages electronic data of the company, and there is a problem that it requires a large cost.

Japanese Unexamined Patent Publication No. 2012-175552

An object of the present invention is to extend the expiration date of a time stamp at a low cost.

(1) In the invention according to claim 1, a secret key storage means for exchanging a private key, a time stamp creating means for creating a time stamp by electronically signing with the stored private key, and the storage. Before the exchange of the private key, the pre-exchange time stamp acquisition means for acquiring the pre-exchange time stamp created by the time stamp creating means using the pre-exchange private key, and the time when the pre-exchange time stamp is created. A proof information acquisition means for acquiring proof information certifying the validity of the private key before the exchange, and a transmission means for transmitting the acquired pre-exchange time stamp and the proof information to a storage server operated by a predetermined institution. The pre-exchange time stamp is the last time stamp created by the pre-exchange private key .
(2) In the invention described in claim 2, wherein the certification information acquisition means Tokushi preparative revocation information of the public key to verify the validity of the public key paired with the secret key before the exchange, the secret key After exchanging the private key stored in the storage means, the revocation information time stamp acquisition means for acquiring the revocation information time stamp created by the time stamp creation means for the acquired revocation information is further provided, and the transmission means is provided with the revocation information time stamp acquisition means. The time stamp server according to claim 1, wherein the acquired revocation information time stamp is transmitted to the storage server as the certification information.
( 3 ) In the invention according to claim 3 , the revocation information storage means for storing the acquired revocation information and the stored revocation information are transmitted to the predetermined terminal when requested by the predetermined terminal. The time stamp server according to claim 2, further comprising a revocation information transmission means.
( 4 ) In the invention according to claim 4 , the time stamp acquisition means for acquiring the first time stamp whose expiration date has passed to prove the non-tampering property of the electronic data and the acquired first time stamp are created. A second time stamp created after the time stamp by the private key used to do so, and a proof that proves the validity of the private key at the time when the second time stamp is created. First, the validity of the private key at the time of creating the second time stamp is confirmed by the time stamp certification information acquisition means for acquiring the information from the storage server operated by a predetermined institution and the acquired certification information. The confirmation means, the second confirmation means for confirming the validity of the acquired first time stamp using the confirmed second time stamp, and the electron using the confirmed first time stamp. Provided is a verification device provided with a third confirmation means for confirming the non-tampering property of data.
( 5 ) In the invention according to claim 5 , a time stamp creation function for creating a time stamp by electronically signing with the stored private key in a computer provided with a private key storage means for exchanging the private key. And, before the exchange of the stored private key, the pre-exchange time stamp acquisition function for acquiring the pre-exchange time stamp created by the time stamp creation function using the pre-exchange private key, and the pre-exchange time stamp The proof information acquisition function that acquires the proof information that certifies the validity of the private key before the exchange at the time of creation, and the acquired pre-exchange time stamp and the proof information are transmitted to the storage server operated by a predetermined institution. The transmission function is realized by a computer, and the pre-exchange time stamp is the last time stamp created by the pre-exchange private key, and provides a time stamp expiration date extension program.
( 6 ) In the invention according to claim 6 , a time stamp acquisition function for acquiring a first time stamp whose expiration date has passed to prove the non-tampering property of electronic data and the acquired first time stamp are created. A second time stamp created after the time stamp by the private key used to do so, and a proof that proves the validity of the private key at the time when the second time stamp is created. The first to confirm the validity of the private key at the time of creating the second time stamp by the time stamp certification information acquisition function for acquiring the information from the storage server operated by a predetermined institution and the acquired certification information. The confirmation function, the second confirmation function for confirming the validity of the acquired first time stamp using the confirmed second time stamp, and the electron using the confirmed second time stamp. A third confirmation function for confirming the non-tampering of data and a verification program for realizing the non-tampering property of data are provided.

According to the present invention, the expiration date of the time stamp token can be extended at low cost by storing the information indicating the validity of the private key before the exchange.

It is a figure which showed the structure of the time stamp system of this embodiment. It is the figure which showed typically the hardware composition of the time stamp server and the terminal. It is a figure for demonstrating the expiration date of a TSA certificate. It is a flowchart for demonstrating the procedure of the expiration date extension processing. It is a flowchart for demonstrating the procedure for verifying TST with an extended expiration date. It is a figure for demonstrating a modification.

(1) Outline of Embodiment Before switching the pair of the private key A and the TSA certificate 7 to the pair of the private key B and the TSA certificate 9, the time stamp server 2 (FIG. 1) sets the final TST21 for the user. After issuance, the time stamp is performed only once with the private key A, and the TST (TSA) 22 is retained.
Further, the time stamp server 2 acquires and holds the CRL33 (TSA certificate revocation information) issued after the exchange of the private key A and the TSA certificate 7 from the certificate authority server 3, and holds the private key. Issue TST (CRL) 25 at B.
In addition, the time stamp server 2 acquires the CA certificate 34 from the certificate authority server 3, and issues the TST (CA) 26 to the CA certificate 34 using the private key B.

Then, the time stamp server 2 transmits the held TST (TSA) 22, TST (CRL) 25, and TST (CA) 26 as a set to the storage station server 4 operated by a public third-party organization. Deposit.
After depositing, the time stamp server 2 saves the TSA certificate 7 and the CRL 33, which are the originals of the TST (TSA) 22, and makes them available to the user.
The time stamp server 2 performs the above processing every time the private key and the TSA certificate are exchanged.

On the other hand, the user's terminal acquires the TSA certificate 7 and the CRL 33 from the time stamp server 2, and acquires the TST (TSA) 22, TST (CRL) 25, and TST (CA) 26 from the certificate authority server 3. ..
The non-tampering property of TSA certificate 7 and CRL33 can be verified by the deposited TST (TSA) 22, TST (CRL) 25, TST (CA) 26, and further, TSA certificate 7 becomes CRL33. The validity of the TSA certificate 7 can be verified by not being listed.

After confirming the identity between the TSA certificate 7 whose validity has been confirmed in this way and the TSA certificate 7 of the TST21 that the terminal has, the terminal verifies the electronic data to be verified for non-tampering by the TST21. To do.
In this way, the non-tampering property of the TST (TSA) 22 issued by the private key A after the TST 21 can be confirmed by using the information provided by the time stamp server 2 and the storage station server 4, so that the non-tampering property can be confirmed before this. The validity of the TST21 issued with the private key A is guaranteed.

As described above, in the time stamp server 2, the last TST (TSA) 22 issued by the private key A and the TSA certificate 7 before the exchange, and the private key A and the TSA certificate 7 at that time are invalid. The expiration date of TST can be extended without reacquiring the time stamp by storing it together with CRL33 (Certificate Revocation List), which is information indicating that the time stamp was not available, at a public third-party organization. it can.

(2) Details of the Embodiment FIG. 1 is a diagram showing the configuration of the time stamp system 1 of the present embodiment.
The time stamp system 1 is configured by disposing a time stamp server 2, a certificate authority server 3, a storage station server 4, and a plurality of terminals (not shown) so as to be able to communicate with each other via a communication network such as the Internet.

The time stamp server 2 is a time stamp unit (TSU) operated by a TSA station (time certificate authority), and a secret key A (also called a signature key or TSA key) is secretly attached to an HSM (Hardware Security Module) 5. It is stored in an exchangeable manner with the key, and the TSA (Time Stamping Authority) certificate 7 of the public key A corresponding to the private key A is also stored in an exchangeable manner.
The HSM 5 hardware prevents the leakage of the private key A, assigns the current date and time to the hash value of the time stamp creation target, and digitally signs the private key A.
As described above, the time stamp server 2 is provided with a private key storage means for exchanging the private key.

The time stamp issuing unit 10 is an application that issues a TST (Time Stamp Token) using HSM5 in response to a request from a user (customer) terminal, and a time stamp is digitally signed with a private key. Functions as a means for creating a time stamp.

More specifically, when the time stamp issuing unit 10 receives the hash value (hash value of the electronic data to be issued by the time stamp) transmitted from the user's terminal, the time stamp issuing unit 10 is currently working with the HSM 5 to receive the hash value. Add the date and time, TSA certificate 7, which is a certificate of public key A, and other necessary information (for example, CRL or CA certificate described later), and digitally sign with private key A (that is, these information). (Encrypted by the private key A), and the encrypted information is added to these information to generate TST21. Sometimes TST is simply called a time stamp.
Since the encrypted information can be decrypted only by the public key A paired with the private key A, the success of the decryption by the public key A means that this information was certainly generated by the time stamp issuing unit 10. You can check. Similarly, the non-tampering property of the electronic signature encrypted with the private key B can be confirmed by decryption with the public key B.
The time stamp server 2 transmits the TST 21 created by the time stamp issuing unit 10 to the user's terminal, and the user stores the TST 21 as evidence of non-tampering with electronic data.

The certificate authority server 3 is a server operated by a CA station (CA: Certification Authority, certificate authority).
The certificate authority server 3 includes a certificate issuing unit 31 and a revocation information disclosure unit 32.
The certificate issuing unit 31 issues a CA certificate 34 that certifies the certificate authority itself.
The revocation information disclosure unit 32 continuously collects information on the revoked public key and issues a CRL (Certificate Revocation List) 33 listing the TSA certificates of the revoked public key.
The interval at which the CRL is issued varies depending on the certificate authority, for example, once a day or every few hours.

The storage station server 4 is a server operated by a public third-party organization such as the government, an organization equivalent thereto, and an industry group, and functions as a storage server operated by a predetermined organization.
The storage station server 4 receives TST registrations from the time stamp server 2, stores them, and provides them when requested.
Since the storage station server 4 has high reliability, it is considered that the TST stored in the storage station server 4 is not tampered with.

The configuration of the time stamp system 1 is as described above, but the TST21 issued in this way has an expiration date (for example, 10 years from the issuance) set in consideration of the compromise of the private key A. ..
Further, in order to further enhance security, the TSA station operates to exchange the private key stored in the HSM 5 and the TSA certificate paired with the private key every predetermined period (for example, every year).

In order to deal with this, the time stamp server 2 cooperates with the certificate authority server 3 and the storage station server 4 in addition to the normal business of issuing TST21, so that the time stamp server 2 is a secret that is a pair of a private key and a public key before exchange. At the timing of exchanging the key A and the TSA certificate 7 for the exchanged private key and the public key pair, the private key B and the TSA certificate 9 (certificate of the public key B), the TST21 is as follows. Performs expiration date extension processing.

First, the time stamp server 2 uses the private key A and the TSA certificate 7 to perform the final TST (once after issuing the final TST 21 to the user) before exchanging the private key A for the private key B. ) TST (TSA) 22 is issued.
In the present embodiment, the original data of the TST (TSA) 22 is the TSA certificate 7, but the electronic data to be issued may be arbitrary.

In this way, the time stamp server 2 is the pre-exchange time stamp (TST (TSA) 22), which is the last time stamp created by the time stamp creating means using the pre-exchange private key A before the exchange of the private key A. ) Is provided with a pre-exchange time stamp acquisition means.

Next, the time stamp system 1 waits for a predetermined period after exchanging the private key A and the TSA certificate 7 for the private key B and the TSA certificate 9.
This predetermined period is set in consideration of the time difference until the certificate authority server 3 collects the revocation information at the time when the time stamp server 2 issues the TST (TSA) 22 using the private key A.
This is because if the CRL 33 at the time of issuing the TST (TSA) 22 does not include the TSA certificate 7, it can be proved that the private key A was valid at the time of issuing the TST (TSA) 22.

After waiting for a predetermined period, the time stamp server 2 obtains the CRL 33 and the CA certificate 34 from the certificate authority server 3, and uses the private key B and the TSA certificate 9 for the TST (CRL) 25 for the CRL 33 and the CA certificate 34. Issue TST (CA) 26.

As described above, the time stamp server 2 includes a proof information acquisition means for acquiring proof information certifying the validity of the private key A before exchange at the time when the pre-exchange time stamp (TST (TSA) 22) is created. ing.
Then, the proof information acquisition means acquires the revocation information (CRL33) of the public key that proves the validity of the public key paired with the private key before exchange as proof information.

Further, the time stamp server 2 is a revocation information time stamp acquisition means for acquiring the revocation information time stamp (TST (CRL) 25) created for the revocation information (CRL33) by the time stamp creation means after exchanging the private key A. It has.

Since the revocation information disclosure unit 32 updates the CRL 33 sequentially and does not save the old one, the time stamp server 2 saves the TSA certificate 7 and certifies the CRL 33 and the CA so that the user can verify the TST 21 at a later date. Also remember Book 34.

Here, the CA certificate 34 is not necessarily essential for the verification of the TST21, but can be used to more reliably confirm the validity of the TST21.
Then, when there is a request from the user's terminal, the time stamp server 2 transmits the stored TSA certificate 7 and CRL 33 to the terminal.

As described above, the time stamp server 2 is provided with the revocation information storage means for storing the revocation information (CRL33).
Then, the time stamp server 2 includes a revocation information transmitting means for transmitting the stored revocation information to the predetermined terminal when a request is made from the predetermined terminal.

When the time stamp server 2 generates TST (TSA) 22, TST (CRL) 25, and TST (CA) 26 in this way, they are associated with each other and transmitted to the storage station server 4, and stored in the storage station server 4.・ Request storage.
In this way, the time stamp server 2 transmits the pre-exchange time stamp (TST (TSA) 22) and the certification information (TST (CRL) 25) to the storage server (storage station server 4) operated by a predetermined institution. The means are provided, and the transmitting means transmits the revocation information time stamp as proof information to the storage server.

The method of association may be arbitrary as long as it is specified by the storage station server 4, but for example, these three TSTs can be stored in one folder or combined into one archive file. it can.
In any case, the user can obtain these three TSTs from the storage station server 4 at the time of verification of the TST21.

The expiration date extension process of TST21 is as described above, and since these processes are performed by the time stamp server 2 when exchanging the private key and the TSA certificate, the user of TST21 does not do anything in particular and the expiration date of TST21 is expired. Can be extended.

On the other hand, the non-tampering verification using TST21 can be performed as follows.
The user's terminal, which functions as a verification device, stores the original electronic data and the TST21 whose expiration date has passed for confirming the non-tampering property of the original electronic data.
As described above, the terminal is provided with a time stamp acquisition means for acquiring the first time stamp (TST21) whose expiration date has passed, which proves the non-tampering property of the electronic data.

Then, when the terminal verifies the TST21 at hand, the time stamp server 2 displays the TSA certificate 7 used for issuing the TST21 and the CRL33 stored (published) in combination with the TSA certificate 7. to download.

Next, the TST (TSA) 22 and the TST (CRL) 25 acquired for the TSA certificate 7 and the CRL 33 are downloaded from the storage station server 4.
In this way, the terminal has a second time stamp (TST (TSA) 22) created after the time stamp by the private key A used to create the first time stamp, and the second time stamp. Obtain the proof information (TST (CRL) 25) certifying the validity of the private key A at the time when the time stamp of 2 is created from the storage server (storage station server 4) operated by a predetermined institution. It is equipped with a means for acquiring time stamp certification information.
Since the CRL 33 exerts a proof ability by the TST (CRL) 25, the TST (CRL) 25 functions as proof information.

Then, the terminal performs the non-tampering property of the CRL 33 acquired from the time stamp server 2 by the TST (CRL) 25 acquired from the storage station server 4, and stores the non-tampering property of the TSA certificate 7 acquired from the time stamp server 2. This is performed by the TST (TSA) 22 acquired from the station server 4.

Then, after confirming that the CRL 33 and the TSA certificate 7 have not been tampered with, the terminal does not include the TSA certificate 7 in the list of the CRL 33, so that the private key A at the time of creating the TST (TSA) 22 Check the effectiveness.
As described above, the terminal is provided with the first confirmation means for confirming the validity of the private key A at the time of creating the second time stamp (TST (TSA) 22) by using the proof information (TST (CRL) 25). There is.

Next, the terminal compares the TSA certificate 7 confirmed to be non-tampering with the TSA certificate 7 included in the TST21 to be verified at hand, and the same TSA certificate 7 is used. If is confirmed, the validity of TST (TSA) 22 issued after TST21 can be confirmed, so that the non-tampering property of TST21 can be confirmed.
As described above, the terminal is provided with a second confirmation means for confirming the validity of the first time stamp (TST21) by using the second time stamp (TST (TSA) 22).

Then, the terminal uses TST21 to verify the non-tampering property of the original electronic data.
As described above, the terminal is provided with a third confirmation means for confirming the non-tampering property of the electronic data by using the first time stamp for confirming the non-tampering property.

In the above configuration, the non-tampering property of the TSA certificate 7 provided by the time stamp server 2 to the user is confirmed by the TST (TSA) 22, and then the TSA certificate 7 and the TSA certificate 7 of the TST 21 are checked. Although the non-tampering property of the TSA certificate 7 of the TST21 was confirmed by comparison, the non-tampering property of the TSA certificate 7 of the TST21 can be directly confirmed by using TST (TSA) 22.

In the above, the time stamp server 2 is configured to associate TST (TSA) 22, TST (CRL) 25, and TST (CA) 26 and transmit them to the storage station server 4, but the correspondence is the time stamp server 2. The storage station server 4 can be configured to deposit these three TSTs individually.
In this case, the terminal inquires the time stamp server 2 for the correspondence, and individually acquires TST (TSA) 22, TST (CRL) 25, and TST (CA) 26 from the storage station server 4 according to the instruction of the time stamp server 2. To do.

FIG. 2A is a diagram schematically showing a hardware configuration of the time stamp server 2.
The time stamp server 2 is configured by connecting a CPU 51, a ROM 52, a RAM 53, a communication control unit 54, a storage device 55, and an HSM 5, and functions as a computer provided with a secret key storage means for exchanging a private key. doing.

The CPU 51 is a central processing unit, and operates according to a time stamp issuing program (not shown) or a TST expiration date extension program stored in the storage device 55.
The CPU 51 executes the TST issuing process for the user by executing the time stamp issuing program, and performs the expiration date extension processing of the TST 21 by executing the expiration date extension program.

The ROM 52 is a read-only memory that stores basic programs and parameters for operating the CPU 51.
The RAM 53 is a readable and writable memory, and provides a working memory when the CPU 51 issues a TST 21 or performs a process of extending the expiration date of the TST 21.

The communication control unit 54 is an interface for connecting the time stamp server 2 to the certificate authority server 3, the storage station server 4, and the user's terminal.
The storage device 55 is configured by using a storage medium such as a hard disk, and stores programs such as a time stamp issuing program and an expiration date extension program, as well as TSA certificate 7, CRL33, CA certificate 34, and the like. Store data.

The HSM 5 is composed of, for example, independent hardware and is connected to the CPU 51 via a predetermined interface.
The HSM 5 has a day / time measurement function and an electronic signature function in addition to storing the private key A, and creates a TST in cooperation with the CPU 51.
Since the HSM5 creates the private key A and the TST in a hardware-protected environment, security can be enhanced.

FIG. 2B is a diagram schematically showing a hardware configuration of a terminal.
The terminal is configured by connecting a CPU 61, a ROM 62, a RAM 63, a communication control unit 64, a storage device 65, an input unit 66, and an output unit 67.

The CPU 61 is a central processing unit and operates according to a time stamp verification program (not shown) stored in the storage device 65.
By executing the verification program, the CPU 61 can substantially extend the expiration date of the TST 21 in cooperation with the time stamp server 2 and the storage station server 4.

The ROM 62 is a read-only memory that stores basic programs and parameters for operating the CPU 61.
The RAM 63 is a readable and writable memory, and provides a working memory when the CPU 61 verifies the TST 21.

The communication control unit 64 is an interface for connecting the terminal to the time stamp server 2 and the certificate authority server.
The storage device 65 is configured by using a storage medium such as a hard disk, and stores the verification program and also stores the electronic data and the TST 21 for confirming the non-tampering property of the electronic data.

The input unit 66 includes, for example, an input device such as a keyboard and a mouse, and receives input from the user.
The output unit 67 includes, for example, an output device such as a display, and presents various types of information to the user.

The user operates the operation screen of the time stamp server 2 or the storage station server 4 displayed on the output unit 67 from the input unit 66, downloads the TSA certificate 7 from the time stamp server 2, or TST from the storage station server 4. (TSA) 22, TST (CRL) 25, and TST (CA) 26 can be downloaded.
In addition, the hardware configuration of the certificate authority server 3 and the storage station server 4 is the same as that of the time stamp server 2, and the CPU performs various processes by a predetermined program.

FIG. 3 is a diagram for explaining the expiration date of the TSA certificate 7.
Since the private key A is paired with the TSA certificate 7, the expiration date of the TSA certificate 7 is also the expiration date of the private key A.

As an example, the TSA Bureau guarantees the user a minimum validity period of the TSA Certificate 7 for 10 years.
Further, the time stamp server 2 exchanges the private key every year, and it is estimated that the period required for the exchange is one month.
Therefore, the TSA station sets a validity period of 10 years + 1 year + 1 month for the TSA certificate 7 for a total of 11 years and 1 month.

As shown in FIG. 3, the TSA certificate 7 is handed over to the private key B after the activation period of less than one year and one month (the period in which the HSM 5 issues a time stamp with the private key A). At the same time, it is taken over by the TSA certificate 9.
In this way, by deleting the private key A from the HSM5, it is possible to eliminate the risk of compromise (leakage) and create a state in which it does not expire (other than the compromise of the cryptographic algorithm).

FIG. 4 is a flowchart for explaining the procedure of the expiration date extension process.
The following processing is performed by the CPUs of the time stamp server 2, the certificate authority server 3, and the storage station server 4 according to a predetermined program.

First, the time stamp server 2 creates the final TST (TSA) 22 for the TSA certificate 7 before exchanging the private key A for the private key B (step 5).
Then, the time stamp server 2 stores the TSA certificate 7 and the TST (TSA) 22 in the storage device 55.

Next, the time stamp server 2 exchanges the private key A for the private key B and the TSA certificate 7 for the TSA certificate 9 (step 10).
The time stamp server 2 stores the TSA certificate 7 in the storage device 55 for verification by the terminal, but the private key A is erased from the HSM 5 from the viewpoint of security.

After exchanging the private key A and the TSA certificate 7, the time stamp server 2 waits until the latest CRL33, which should be posted if the TSA certificate 7 is revoked, is issued.
During this period, the issuance of TST by the private key B is started.

After waiting until a predetermined time point until the latest CRL33 is issued, the time stamp server 2 requests the certificate authority server 3 to transmit the CRL33 (step 15).
On the other hand, the certificate authority server 3 transmits the CRL 33 to the time stamp server 2 (step 20).

When the time stamp server 2 receives the CRL 33 from the certificate authority server 3, it issues a time stamp with the private key B and creates the TST (CRL) 25 (step 25).
Then, the time stamp server 2 stores the CRL 33 and the TST (CRL) 25 in the storage device 55.

Next, the time stamp server 2 requests the certificate authority server 3 to transmit the CA certificate 34 (step 30).
On the other hand, the certificate authority server 3 transmits the CA certificate 34 to the time stamp server 2 (step 35).

When the time stamp server 2 receives the CA certificate 34 from the certificate authority server 3, it issues a time stamp with the private key B and creates the TST (CA) 26 (step 40).
Then, the time stamp server 2 stores the CA certificate 34 and the TST (CA) 26 in the storage device 55.

Next, the time stamp server 2 transmits the three TSTs of TST (TSA) 22, TST (CRL) 25, and TST (CA) 26 to the storage station server 4 in association with each other (step 45).
The storage station server 4 receives and stores these three TSTs (step 50).

FIG. 5 is a flowchart for explaining a procedure for verifying the TST 21 having an extended expiration date.
First, the terminal acquires and stores the electronic data to be verified for non-tampering and the TST21 issued for the electronic data (step 100).

Next, the terminal requests the time stamp server 2 for the TSA certificate 7 used for creating the TST 21 and the CRL 33 paired with the TSA certificate 7 (step 105).
On the other hand, the time stamp server 2 reads the TSA certificate 7 and the CRL 33 from the storage device 55 and transmits them to the terminal (step 110).

Next, the terminal requests the storage station server 4 for TST (TSA) 22 and TST (CRL) 25 (step 115). Although not shown, TST (CA) 26 may be further requested.
On the other hand, the storage station server 4 transmits TST (TSA) 22 and TST (CRL) 25, and TST (CA) 26 when requested (step 120).

The terminal receives TST (TSA) 22 and TST (CRL) 25 from the storage station server 4, and first verifies the CRL 33 downloaded from the time stamp server 2 by TST (CRL) 25 (step 125).
More specifically, the terminal takes out the public key B from the TST (CRL) 25 and uses it to decrypt the electronic signature in the TST (CRL) 25 so that the non-CRL 33 contained in the TST (CRL) 25 is non-CRL 33. Check for tampering. Further, the verification is performed by confirming the identity between the CRL 33 confirmed to be non-tampering and the CRL 33 downloaded from the time stamp server 2.

Next, the terminal verifies the TSA certificate 7 downloaded from the time stamp server 2 with the TST (TSA) 22, and confirms that the TSA certificate 7 is not included in the verified CRL33, thereby confirming that the TSA certificate 7 is not included in the verified CRL33. The non-tampering property and effectiveness of 7 are verified (step 130).

The terminal compares the TSA certificate 7 whose non-tampering property and validity have been confirmed with the TSA certificate 7 included in the TST21 to be verified, and verifies their identity to verify the latter TSA certificate. Confirm the non-tampering property and effectiveness of 7 (step 135).
Next, the terminal verifies the non-tampering property of the electronic data to be verified by using the TSA certificate 7 of TST21 whose non-tampering property and validity have been confirmed (step 140).
Although TST21 can be verified by the above processing, TST (CA) 26 may be further verified.

FIG. 6A is a diagram for explaining a modification 1 of the present embodiment.
In the embodiment, the CRL 33 and the CA certificate 34 are digitally signed with the private key B to generate the TST (CRL) 25 and the TST (CA) 26, but the CRL 33 and the CA certificate 34 themselves are signed by the certificate authority server 3. In the first modification, the time stamp server 2 transmits the CRL 33 and the CA certificate 34 as they are to the storage authority server 4 and registers them.
As described above, the time stamp server 2 of the modification 1 transmits the TST (TSA) 22, the CRL 33, and the CA certificate 34 to the storage authority server 4 and registers them.

When verifying, the terminal acquires the TSA certificate 7 from the time stamp server 2 and the TST (TSA) 22 and the CRL 33 from the storage station server 4.
Then, after confirming the non-tampering property of the TSA certificate 7 acquired from the time stamp server 2 with the TST (TSA) 22, the terminal does not describe the TSA certificate 7 in the CRL 33, so that the TSA certificate Confirm the effectiveness of 7. Then, the TSA certificate 7 whose validity has been confirmed is compared with the TSA certificate 7 of the electronic data to be verified, and the non-tampering property and validity of the latter TSA certificate 7 are confirmed.

FIG. 6B is a diagram for explaining a modification 2 of the present embodiment.
The time stamp server 2 of the modification 2 synthesizes the CRL 33 and the CA certificate 34 into one file such as an archive file, and issues a time stamp to the file with the private key B, so that the TSA certificate 9 can be obtained. Generate the given TST80.
The time stamp server 2 stores the synthesized file in the storage device 55, and transmits the TST (TSA) 22 and the TST 80 to the storage station server 4 for registration.

When verifying, the terminal acquires the file synthesized with the TSA certificate 7 from the time stamp server 2, and acquires TST (TSA) 22 and TST80 from the storage station server 4.
Then, the terminal confirms the non-tampering property of the synthesized file with TST80, and confirms the non-tampering property of the TSA certificate 7 obtained from the time stamp server 2 with TST (TSA) 22.
Next, the validity of the TSA certificate 7 is confirmed by not describing the TSA certificate 7 in the CRL 33 included in the synthesized file.
Finally, the non-tampering property and validity of the latter TSA certificate 7 are confirmed by comparing the TSA certificate 7 whose non-tampering property and validity have been confirmed with the TSA certificate 7 of electronic data.

FIG. 6C is a diagram for explaining a modification 3 of the present embodiment.
The time stamp server 2 of the modification 3 synthesizes the TST (TSA) 22, the CRL 33, and the CA certificate 34 into one file such as an archive file, and issues a time stamp to the file with the private key B. Generates a TST81 with a TSA certificate 9.
The time stamp server 2 stores the synthesized file in the storage device 55, and transmits the TST81 to the storage station server 4 for registration.

When verifying, the terminal acquires the TSA certificate 7 and the synthesized file from the time stamp server 2, and acquires the TST81 from the storage station server 4.
Then, the terminal confirms the non-tampering property of the synthesized file with TST81, and confirms the non-tampering property of the TSA certificate 7 acquired from the time stamp server 2 with TST (TSA) 22 included in the synthesized file.
Next, the validity of the TSA certificate 7 is confirmed by not describing the TSA certificate 7 obtained from the time stamp server 2 in the CRL 33 included in the synthesized file.
Finally, the TSA certificate 7 whose validity has been confirmed is compared with the TSA certificate 7 of the electronic data, and the non-tampering property and validity of the latter TSA certificate 7 are confirmed.

According to the embodiment described above, the following effects can be obtained.
(1) By the processing on the time stamp business side, the expiration date of the time stamp issued to the user can be substantially extended without requiring the processing on the user side.
(2) Since the user side can omit the processing related to the extension such as selection of the file requiring the extension of the time stamp expiration date and collection of various information necessary for the extension, the cost can be greatly reduced.
(3) By depositing the last time stamp issued by the private key A and the CRL33 indicating the validity of the private key in the storage station server 4, the validity of the time stamp by the private key A is confirmed by the expiration date of the private key A. It can be secured later.

1 Time stamp system 2 Time stamp server 3 Certificate authority server 4 Storage station server 5 HSM
7 TSA certificate 9 TSA certificate 10 Time stamp issuer 21 TST
22 TST (TSA)
25 TST (CRL)
26 TST (CA)
31 Certificate Issuing Department 32 Revocation Information Disclosure Department 33 CRL
34 CA certificate 51 CPU
52 ROM
53 RAM
54 Communication control unit 55 Storage device 61 CPU
62 ROM
63 RAM
64 Communication control unit 65 Storage device 66 Input unit 67 Output unit 80, 81 TST

Claims (6)

A secret key storage means for exchanging private keys and
A time stamp creation means for creating a time stamp by electronically signing with the stored private key,
Before the exchange of the stored private key, the pre-exchange time stamp acquisition means for acquiring the pre-exchange time stamp created by the time stamp creating means using the pre-exchange private key, and the pre-exchange time stamp acquisition means.
Proof information acquisition means for acquiring proof information certifying the validity of the private key before exchange at the time when the pre-exchange time stamp is created, and
A transmission means for transmitting the acquired pre-exchange time stamp and the certification information to a storage server operated by a predetermined institution, and
Equipped with,
The pre-exchange time stamp is the last time stamp created with the pre-exchange private key.
A time stamp server that features that. The certification information acquisition means Tokushi preparative revocation information of the public key to verify the validity of the public key paired with the secret key before the exchange,
After exchanging the private key stored in the private key storage means, the revocation information time stamp acquisition means for acquiring the revocation information time stamp created by the time stamp creation means for the acquired revocation information is further provided.
The transmission means transmits the acquired revocation information time stamp as the certification information to the storage server.
The time stamp server according to claim 1. The revocation information storage means for storing the acquired revocation information and
When there is a request from a predetermined terminal, the revocation information transmitting means for transmitting the stored revocation information to the predetermined terminal, and
The time stamp server according to claim 2, wherein the time stamp server is provided. A time stamp acquisition means for acquiring the first time stamp whose expiration date has passed to prove that the electronic data is not tampered with,
With the private key used to create the acquired first time stamp, the second time stamp created after the time stamp and the time when the second time stamp is created, Proof information certifying the validity of the private key, a time stamp proof information acquisition means for acquiring from a storage server operated by a predetermined institution, and
With the acquired proof information, a first confirmation means for confirming the validity of the private key at the time of creating the second time stamp, and
A second confirmation means for confirming the validity of the acquired first time stamp using the confirmed second time stamp, and
A third confirmation means for confirming the non-tampering property of the electronic data using the confirmed first time stamp, and a third confirmation means.
A verification device characterized by being equipped with. In a computer equipped with a private key storage means that exchangeably stores the private key,
A time stamp creation function that creates a time stamp by digitally signing with the stored private key,
Before the exchange of the stored private key, the pre-exchange time stamp acquisition function for acquiring the pre-exchange time stamp created by the time stamp creation function using the pre-exchange private key, and the pre-exchange time stamp acquisition function.
A proof information acquisition function for acquiring proof information certifying the validity of the private key before exchange at the time when the pre-exchange time stamp is created, and
A transmission function that transmits the acquired pre-exchange time stamp and the certification information to a storage server operated by a predetermined institution, and
Is realized on a computer,
The pre-exchange time stamp is the last time stamp created with the pre-exchange private key.
The time stamp expiration date extension program is characterized by this. A time stamp acquisition function that acquires the first time stamp whose expiration date has passed to prove that the electronic data is not tampered with,
With the private key used to create the acquired first time stamp, the second time stamp created after the time stamp and the time when the second time stamp is created, A time stamp certification information acquisition function that acquires certification information that proves the validity of the private key from a storage server operated by a predetermined institution, and
A first confirmation function for confirming the validity of the private key at the time of creating the second time stamp based on the acquired proof information, and
A second confirmation function for confirming the validity of the acquired first time stamp using the confirmed second time stamp, and
A third confirmation function for confirming the non-tampering property of the electronic data using the confirmed second time stamp, and a third confirmation function.
A verification program that realizes on a computer.

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