Digital signatures with an embedded view

• US 7,568,101 B1
• Filed: 05/13/2004
• Issued: 07/28/2009
• Est. Priority Date: 05/13/2004
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Narendran, Arungundram, Catorcini, Alessandro, Velzen, Danny van, Cris, Mihaela C.
• Primary Examiner(s): Moazzami; Nasser G
• Assistant Examiner(s): Louie; Oscar A
• Application Number:
  US10/846,428
• Time in Patent Office: 1,902 Days
• Field of Search: 713/176
• US Class Current: 713/176
• CPC Class Codes: H04L 2209/68 Special signature format, e.g. XML format
• CPC Class Codes: H04L 9/3247 involving digital signatures

Abstract

Digital signatures having an embedded view of signed data that lock the signed data but permit it to be repurposed are described. One of these digital signatures can be repurposed for signature by others, such as co-signers or counter-signers. Another of these digital signatures includes embedded information sufficient to recreate the embedded view using the signed data. A method for building a digital signature is also described that permits signing different parts of an electronic document.

Claims

1. A computer-readable medium storing a digital signature, wherein the digital signature comprises an embedded view of signed data, the embedded view locking the signed data and comprising a visual representation of the signed data as seen by a signer if signing the signed data, and wherein the embedded view permits the signed data to be repurposed to allow the signed data to be co-signed or counter-signed, wherein the digital signature further comprises embedded information sufficient to recreate the embedded view from the signed data, the embedded information including one or more specifications of a computing environment used to present the visual representation, and wherein the digital signature further comprises a signature block comprising an XML tag indicating the signed data from other data of an electronic document.

2. The computer-readable medium of claim 1, wherein the digital signature further comprises embedded comments received from the signer.

3. The computer-readable medium of claim 1, wherein the digital signature further comprises embedded custom information.

4. The computer-readable medium of claim 3, wherein the embedded custom information comprises a physical location of the signer.

5. The computer-readable medium of claim 3, wherein the embedded custom information comprises custom user code extending the digital signature.

6. The computer-readable medium of claim 1, wherein the digital signature further comprises the signed data.

7. The computer-readable medium of claim 1, wherein the signed data is part of an electronic document.

8. The computer-readable medium of claim 1, wherein the digital signature further comprises a strong cryptographic hash computed over the embedded view and the signed data effective to lock the embedded view and the signed data.

9. The computer-readable medium of claim 1, wherein the signed data comprises extensible markup language.

10. A computer-readable medium storing a digital signature comprising a static image of signed data when signed, wherein the digital signature is configured to lock the signed data and permit the signed data to be repurposed, the digital signature further comprising embedded information sufficient to recreate a view of the signed data that is identical to the static image, the embedded information including one or more specifications of a computing environment used to present the signed data, wherein the view provides a first visual representation associated with the signed data as seen by a signer if signing the signed data, and wherein the digital signature is further configured to permit at least one of:

viewing a second visual representation of the signed data different than the first visual representation;

or

co-signing or counter-signing the signed data.

11. The computer-readable medium of claim 10, wherein the sufficient information indicates an operating system version and a number of monitors.

12. One or more computer-readable media storing computer executable instructions that, when executed by a computer, perform a method comprising:

embedding a static image of data into a signature block of a digital signature, wherein at least a portion of the data is identifiable as signed data that is repurposable allowing a second digital signature of the signed data to be built, and wherein the static image provides a visual representation of the signed data as seen by a signer if signing the signed data, wherein the signature block comprises an XML tag indicating the repurposable signed data; and

embedding information into the digital signature sufficient to recreate the static image from the signed data, the embedded information including one or more specifications of a computing environment used to present the static image.

13. The computer-readable media of claim 12, wherein the acts further comprise embedding a second static image of the signed data into the second digital signature.

14. The computer-readable media of claim 12, wherein the acts further comprise presenting an electronic document comprising the signed data and receiving a selection to sign the signed data.

15. The computer-readable media of claim 12, wherein the acts further comprise embedding a certificate indicating an identity of the signer into the digital signature.

16. The computer-readable media of claim 12, wherein the acts further comprise embedding comments into the digital signature.

17. The computer-readable media of claim 12, wherein the acts further comprise embedding a time-stamp into the digital signature.

18. The computer-readable media of claim 12, wherein the acts further comprise embedding custom information into the digital signature by extending the digital signature.

19. The computer-readable media of claim 12, wherein the acts further comprise locking the digital signature by computing a strong cryptographic hash over the static image and the signed data.

20. A method comprising:

receiving a digital signature having an embedded static image of data, wherein at least a portion of the data is identifiable as signed data, and wherein the embedded static image provides a visual representation of the signed data as seen by a signer if signing the signed data, wherein the digital signature further comprises embedded information sufficient to recreate the static image from the signed data, the embedded information including one or more specifications of a computing environment used to present the static image; and

repurposing the signed data without breaking the digital signature, wherein the act of repurposing comprises;

building a second digital signature of the signed data; and

presenting a static image of the signed data that is different than the embedded static image.

21. The method of claim 20, further comprising recreating the static image from the signed data.