Time stamping system for electronic documents and program medium for the same

• US 20030159048A1
• Filed: 01/10/2003
• Published: 08/21/2003
• Est. Priority Date: 02/20/2002
• Status: Active Grant

• Current Assignee: Amano Corporation
• Original Assignee: Amano Corporation
• Inventors: Sato, Tadahiro, Ichikawa, Keisuke, Matsumoto, Tsutomu
• Granted Patent: US 7,266,698 B2
• Time in Patent Office: Days
• US Class Current: 713/178
• CPC Class Codes: G06F 21/645 using a third party
• CPC Class Codes: G06Q 20/3674 involving authentication
• CPC Class Codes: H04L 9/3247 involving digital signatures
• CPC Class Codes: H04L 9/3297 involving time stamps, e.g. generation of time stamps

Abstract

Object: To provide a time stamping system for electronic documents making it possible to easily provide a time stamp certifying date and time of a document prepared with general purpose document preparation software and also to easily and accurately verify the time data and a program medium for the same.

Solution: The electronic document preparing organization 20 at a client site has a first document preparation terminal device 30 and a second document preparation terminal device 40. When the document preparation terminal device 30 transmits the prepared document and a time stamp request message 31 to the time stamp issuing server 12, and time stamp issuing server 12 assigns electronic signatures with the signature generation secret keys K_s1, K_s2 and returns the data to the document preparation terminal device 30. The document preparation terminal device 40 a document file with the time stamp received from the terminal device 30 assigned therein and a time stamp verification request message 41 to the time stamp verification server 13. The time stamp verification server 13 verifies the time stamp with the signature verification secret key K_v2, and returns a result of the verification. The terminal device 30 and the terminal device 40 can verify the signature and the result of verification respectively with the signature verification public key K_v1.

Claims

1. A time stamping system for electronic documents based on the configuration where a digest value generated based on an electronic document prepared by a client electronic document preparation terminal device with electronic document preparation software incorporated therein is transmitted to an external organization device and the external organization device assigns the time of receipt and an electronic signature to the digest value and returns it to the client, wherein the client electronic document preparation terminal device comprises:

an electronic document reading means for reading an electronic document prepared by the electronic document preparation software;

a digest value computing means for computing a digest value including a hash value as a unidirectional function value based on a read document;

a transmitting means for correlating the digest value to an ID number of the client electronic document preparation terminal device and transmitting the digest value and the ID number to the external organization device;

a receiving means for receiving an electronic certificate transmitted thereto from the external organization device with the term of receipt and the electronic signature assigned to the digest value received by the external organization device as well as to the ID number of the client electronic document preparation terminal device; and

an electronic certificate inserting and writing means for writing the received electronic certificate in the electronic document to be time-stamped stores in the client electronic document preparation terminal device.

2. The time stamping system for electronic documents according to claim 1, wherein said electronic document includes at least original time stamp information describing a digest value for an electronic document to be time-stamped, information indicating the time of receipt of the digest value at an external device, and an ID number of a client device;

public key-signed information prepared by assigning an electronic signature to the original time stamp information with a secret key for the external organization and decodable with a public key for verification of the electronic signature; and

secret key-signed information prepared by electronically signing the original stamp information with a secret key for the external organization and decodable with a secret key for verification of an electronic signature.

3. The time stamping system for electronic documents according to claim 1 or 2 further comprising an offline verification means for computing a digest value for an electronic document to be verified, said electronic document stored in the client terminal device and including a portion other than the electronic certificate buried therein, comparing and verifying the computed digest value to a document digest value in the original tamp stamp information, and also comparing and verifying the original time stamp information according to the decoded public key-signed information by operating the public key for electronic signature verification at the client terminal device.

4. The time stamping system for electronic documents according to claims 1, 2, or 3 further comprising an online verification means for transmitting an electronic certificate written in the electronic document by operating the client terminal device, decoding the secret key-signed information included in the electronic certificate by using the electronic signature verification secret key owned by the external organization, and comparing and verifying the original time stamp information to the decoded secret key-signed information.

5. The time stamping system for electronic documents according to claims 1, 2, or 3 further comprising an online verification means for transmitting at least the secret key-signed information included in the electronic certificate written in the electronic document by operating the client terminal device to the external organization device, decoding the secret key-signed information with the electronic signature verification secret key owned by the external organization to generate information enabling comparison and verification thereof to the electronic document to be verified at the client terminal device, and returning the generated information to the client device.

6. A computer-readable program medium for time-stamping electronic documents with a program recorded therein, said program enabling a computer to realize a function for sending a digest value for an electronic document prepared by a client electronic document preparation terminal device with electronic document preparation software incorporated therein to an external organization device and a function for receiving the electronic certificate returned from the external organization device with the time of receipt and an electronic signature assigned thereby to the digest value, and inserting and writing the electronic certificate in the electronic document to be time-stamped stored in the client electronic document preparation terminal device, wherein said client electronic document preparation terminal device has a program recorded therein for enabling a computer to realize:

an electronic document reading function for reading electronic documents prepared by the electronic document preparation software;

a digest value computing function for computing a digest value from the read electronic document alkoxysilane a unidirectional function value thereof;

a transmitting function for correlating the digest value to an ID number of the client electronic document preparation terminal device and transmitting the digest value and ID number correlated to each other to the external organization device;

a receiving function for receiving the electronic certificate returned from the external organization device with a time stamp and an electronic signature assigned thereto; and

an electronic certificate writing function for writing the returned electronic certificate in an electronic document to be time-stamped prepared by the client electronic document preparation terminal device.

7. A computer readable program medium for time-stamping electronic documents according to claim 6, wherein said electronic certificate includes at least original time stamp information describing a digest value for an electronic document to be time-stamped, the information indicating the time of receipt of the digest value in an external organization device, and an ID number for a client terminal device;

public key-signed information prepared by electrically signing the original time stamp information with a public key owned by the external organization and decodable with an electronic signature verification public key; and

secret key-signed information prepared by electronically signing the original time stamp information with a secret key owned by the external organization and decodable with an electronic signature verification secret key.

8. A computer-readable program medium for time-stamping electronic documents according to claim 6 or 7 further comprising a program enabling a computer to run the offline verification means for computing a digest value for an electronic document to be verified, said electronic document stored in the client terminal device and including a portion other than the electronic certificate buried therein, comparing and verifying the computed digest value to the document digest value included in the original time stamp information, and further comparing and verifying the original time stamp information to the public key-signed information by operating the electronic signature verification public key at the client terminal device.

9. A computer-readable program medium for time-stamping electronic documents according to claim 6, 7, or 8 further comprising a program enabling a computer to run the online verification means for transmitting an electronic certificate written in the electronic document by operating the client terminal device to an external organization device to an external organization device, decoding a secret key-signed information in the electronic document with an electronic signature verification secret key owned by the external organization, and comparing and verifying the original time stamp information to the decoded secret key-signed information.

10. A computer-readable program medium for time-stamping electronic documents according to claim 6, 7, or 8 further comprising a program enabling a computer to run the online verification means for sending at least secret key-signed information of the electronic certificate written in the electronic document by operating the client terminal device to the external organization device, and decoding secret key-signed information with the electronic signature verification key owned by the external organization to generate information comparable and verifiable to the electronic document to be verified in the client terminal device and return the information to the client terminal device.