Time stamping method using aged time stamp receipts

• US 6,993,656 B1
• Filed: 12/10/1999
• Issued: 01/31/2006
• Est. Priority Date: 12/10/1999
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Peyravian, Mohammad, Zunic, Nevenko, Roginsky, Allen, Matyas, Stephen M. Jr.
• Primary Examiner(s): Song, Hosuk
• Assistant Examiner(s): Dada, Beemnet W
• Application Number:
  US09/458,928
• Time in Patent Office: 2,244 Days
• Field of Search: 713/155, 713/178, 713/176, 713/179, 713/158, 713/170, 713/181, 713/501, 713/502, 705/60, 705/75, 705/50, 705/51
• US Class Current: 713/178
• CPC Class Codes: H04L 2209/60 Digital content management, e.g. content distribution
• CPC Class Codes: H04L 2463/121 Timestamp
• CPC Class Codes: H04L 63/123 received data contents, e.g. message integrity
• CPC Class Codes: H04L 9/3297 involving time stamps, e.g. generation of time stamps

Abstract

A method for time stamping a digital document is disclosed. The document originator creates a time stamp receipt by combining the document or other identifying data and a digital time indication. The time stamp receipt is submitted to a time stamping authority having a trusted clock. The time stamping authority optionally validates the time stamp receipt and then computes the age of the time stamp receipt. The time stamping authority creates an aged time stamp receipt by combining the identifying data and time indication contained in the submitted time stamp receipt with the computed age of the time stamp receipt. The time stamping authority cryptographically binds the time information and identifying data in the aged time stamp receipt, e.g., by signing the combination of the identifying data, time indication, and computed age with a private signature generation key.

Claims

1. A computer-implemented method for time stamping a document comprising:

receiving a time stamp receipt at an outside agency, said time stamp receipt including identifying data associated with said document and a time indication;

computing the age of said time stamp receipt based on said time indication;

creating an aged time stamp receipt at said outside agency by combining said identifying data, said time indication and said computed age; and

binding at said outside agency said identifying data, said time indication, and a digital representation of said age using a cryptographic binding scheme to create an aged time stamp receipt.

2. The time stamping method of claim 1 further including transmitting said aged time stamp receipt and binding information generated during said binding operation to a designated party.

3. The time stamping method of claim 1 wherein said identifying data comprises a digital representation of at least a portion of said document.

4. The time stamping method of claim 3 wherein said identifying data comprises a digital sequence derived by application of a deterministic function to at least a portion of said document.

5. The time stamping method of claim 4 wherein said digital sequence is a hash value derived by application of a one-way hashing function to at least a portion of said document.

6. The time stamping method of claim 1 wherein said time stamp receipt further includes an identification number associated with the document originator.

7. The time stamping method of claim 6 wherein said time stamp receipt further includes a sequential record number.

8. The time stamping method of claim 7 further including the step of validating said time stamp receipt at said outside agency.

9. The time stamping method of claim 8 wherein the step of validating said time stamp receipt includes comparing said identification number and sequential record number with data maintained by the outside agency.

10. The time stamping method of claim 1 wherein said binding step includes signing a combination of said identifying data, said time indication, and said digital representation of said age using a digital cryptographic signature scheme.

11. The time stamping method of claim 1 wherein said binding step includes computing a message authentication code on a combination of said identifying data, said time indication, and said digital representation of said age using a secret key controlled by said outside agency.

12. The time stamping method of claim 1 wherein said binding step includes computing a hash value on a combination of said identifying data, said time indication, and said digital representation of said age.

13. The time stamping method of claim 1 wherein said binding step includes encrypting a combination of said identifying data, said time indication, and said digital representation of said age using a secret key controlled by said outside agency.

14. A computer-implemented method for time stamping a document comprising:

creating a time stamp receipt including identifying data associated with said document and a time indication;

transmitting said time stamp receipt to an outside agency for certification;

computing the age of said time stamp receipt at said outside agency;

creating an aged time stamp receipt at said outside agency by combining said identifying data, said time indication and said computed age; and

binding at said outside agency said identifying data, said time indication, and a digital representation of said age using a cryptographic binding scheme to create an aged time stamp receipt.

15. The time stamping method of claim 14 further including transmitting said aged time stamp receipt and binding information generated during said binding operation to a designated party.

16. The time stamping method of claim 14 wherein said identifying data comprises a digital representation of at least a portion of said document.

17. The time stamping method of claim 16 wherein said identifying data comprises a digital sequence derived by application of a deterministic function to at least a portion of said document.

18. The time stamping method of claim 17 wherein said digital sequence is a hash value derived by application of a one-way hashing function to at least a portion of said document.

19. The time stamping method of claim 14 wherein said time stamp receipt further includes an identification number associated with the document originator.

20. The time stamping method of claim 19 wherein said time stamp receipt further includes a sequential record number.

21. The time stamping method of claim 20 further including the step of validating said time stamp receipt at said outside agency.

22. The time stamping method of claim 21 wherein the step of validating said time stamp receipt includes comparing said identification number and sequential record number with data maintained by the outside agency.

23. The time stamping method of claim 14 wherein said binding step includes signing a combination of said identifying data, said time indication, and said digital representation of said age using a digital cryptographic signature scheme.

24. The time stamping method of claim 14 wherein said binding step includes computing a message authentication code on a combination of said identifying data, said time indication, and said digital representation of said age using a secret key controlled by said outside agency.

25. The time stamping method of claim 14 wherein said binding step includes computing a hash value on a combination of said identifying data, said time indication, and said digital representation of said age.

26. The time stamping method of claim 14 wherein said binding step includes encrypting a combination of said identifying data, said time indication, and said digital representation of said age using a secret key controlled by said outside agency.