Time stamping method using time-based signature key

• US 6,965,998 B1
• Filed: 12/10/1999
• Issued: 11/15/2005
• 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): Barron, Jr., Gilberto
• Assistant Examiner(s): Simitoski, Michael J.
• Application Number:
  US09/459,187
• Time in Patent Office: 2,167 Days
• Field of Search: 713/178, 713156-157, 713/155, 713/501, 713/502, 380/30
• US Class Current: 713/178
• CPC Class Codes: H04L 2209/60 Digital content management, e.g. content distribution
• CPC Class Codes: H04L 9/3297 involving time stamps, e.g. generation of time stamps

Abstract

A time-stamping protocol for time-stamping digital documents uses a time-based signature key. A document or other identifying data is sent to a time stamping authority TSA. The TSA has a time-based signature key that the TSA uses to sign time stamp receipts. The signature key is associated with a fixed time reference that is stored in a public key certificate also containing the public verification key. Upon receiving the document, the TSA creates a time stamp receipt by computing a time difference between the time reference associated with the signature key and the time the document was received. The time difference is appended to the document to create a time stamp receipt and the receipt is then signed by the TSA and transmitted to the requestor.

Claims

1. A method for time stamping a document comprising:

receiving identifying data associated with said document at an outside agency;

computing at said outside agency a time difference between a predetermined time reference and the time of receipt of said identifying data;

creating a time stamp receipt by associating said time difference with said identifying data; and

certifying said time stamp receipt by signing said time stamp receipt at said outside agency with a private signature key associated with said predetermined time reference.

2. The time stamping method of claim 1 further including transmitting said certified time stamp receipt to a designated party.

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

4. The time stamping method of claim 3 wherein said identifying data comprises a digital representation of said document 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 representation 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 includes a copy of at least a portion of said identifying data concatenated with said time difference.

7. The time stamping method of claim 6 wherein said time stamp receipt includes a digital sequence derived from said identifying data concatenated with said time difference.

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

9. The time stamping method of claim 8 wherein said time stamp receipt further includes a sequential record number.

10. The time stamping method of claim 1 wherein said time reference is stored in a public key certificate.

11. The time stamping method of claim 1 wherein the step of certifying said time stamp receipt includes encrypting said time stamp receipt using a private signature key controlled by said outside agency, wherein said time stamp receipt can be later verified by decrypting the signed time stamp receipt with a corresponding public verification key.

12. A method for time stamping a document comprising:

receiving identifying data associated with said document at an outside agency;

determining the time of receipt of said identifying data at said outside agency;

computing at said outside agency a time difference between a predetermined time reference and said time of receipt;

associating said time difference with said identifying data to create a time stamp receipt; and

certifying said time stamp receipt by signing said time stamp receipt at said outside agency with a private signature key associated with said predetermined time reference.