Electronic signatures

• US 20050132196A1
• Filed: 12/16/2003
• Published: 06/16/2005
• Est. Priority Date: 12/16/2003
• Status: Active Grant

• Current Assignee: SAP SE
• Original Assignee: SAP AG (SAP SE)
• Inventors: Dietl, Josef
• Granted Patent: US 7,502,934 B2
• Time in Patent Office: Days
• US Class Current: 713/176
• CPC Class Codes: G06F 21/64 Protecting data integrity, e.g. using checksums, certificates or signatures
• CPC Class Codes: H04L 2209/608 Watermarking
• CPC Class Codes: H04L 9/3231 Biological data, e.g. fingerprint, voice or retina network architectures or network communication protocols for supporting authentication of entities using biometrical features in a packet data network H04L63/0861
• CPC Class Codes: H04L 9/3236 using cryptographic hash functions
• CPC Class Codes: H04L 9/3247 involving digital signatures

Abstract

Methods, apparatus, including computer program products, and systems implement and use techniques relating to electronic signatures. In one implementation, a one-way hash is calculated for an electronic document and a digital watermark representing the one-way hash is embedded in a signature document. Based on a user input, the signature document having the embedded digital watermark is altered, and the electronic document is associated with the signature document. The electronic document and the signature document together comprise a signed electronic document. The user input can include biometric information, such as a handwritten signature or a voice recording. For additional security, the one-way hash can be encrypted before a representation of the hash is embedded in the signature document.

Claims

1. A method comprising:

calculating a one-way hash for an electronic document;

embedding a digital watermark representing the one-way hash in a signature document;

based on a user input, altering an appearance of the signature document having the embedded digital watermark; and

associating the electronic document with the signature document, wherein the electronic document and the signature document together comprise a signed electronic document.

2. The method of claim 1, wherein the user input comprises a handwritten signature and altering an appearance of the signature document comprises:

applying a visual representation of the handwritten signature to a graphical representation of the signature document.

3. The method of claim 2, wherein the visual representation of the handwritten signature comprises a black line.

4. The method of claim 1, wherein the user input comprises biometric data and altering an appearance of the signature document comprises:

applying a visual representation of the biometric data to a graphical representation of the signature document.

5. The method of claim 4, wherein the visual representation of the biometric data comprises a black line.

6. The method of claim 1, wherein the signature document is derived from a digital image.

7. The method of claim 1, wherein the one-way hash comprises a checksum.

8. The method of claim 1, further comprising:

encrypting the one-way hash; and

wherein embedding a digital watermark representing the one-way hash in a signature document comprises embedding a digital watermark representing the encrypted one-way hash in the signature document.

9. The method of claim 8, wherein:

encrypting the one-way hash comprises using a private key associated with a device used to calculate the one-way hash.

10. A method comprising:

receiving a signed electronic document comprising an electronic document and a signature document, the signature document including an electronic signature applied to an image and a digital watermark representing a first one-way hash embedded in the image;

obtaining the first one-way hash from the image;

calculating a second one-way hash for the electronic document;

comparing the first one-way hash to the second one-way hash; and

verifying the signed electronic document based at least in part on the one-way hash comparison.

11. The method of claim 10, wherein the electronic signature applied to an image comprises a black line representing a handwritten signature applied to a graphical representation of an image.

12. The method of claim 11, further comprising:

comparing the electronic handwritten signature to a valid signature specimen; and

verifying the signature document based at least in part on the signature comparison.

13. The method of claim 11, further comprising:

inspecting the black line for indications of alterations to the image after the black line was applied.

14. The method of claim 10, wherein the electronic signature applied to an image comprises a black line representing biometric data applied to a graphical representation of an image.

15. The method of claim 14, further comprising:

comparing the biometric data to expected biometric data; and

verifying the signature document based at least in part on the comparison of biometric data.

16. The method of claim 14, further comprising:

inspecting the black line for indications of alterations to the image after the black line was applied.

17. The method of claim 10, wherein the digital watermark represents an encrypted one-way hash, the method further comprising:

decrypting the one-way hash; and

comparing the decrypted one-way hash to the second one-way hash.

18. The method of claim 17, wherein decrypting the one-way hash comprises using a public key associated with a device used to encrypt the one-way hash.

19. A system comprising:

a processor configured to;

calculate a one-way hash of an electronic document;

embed a digital watermark representing the one-way hash in a signature document;

based on a user input, alter an appearance of the signature document having the embedded digital watermark; and

associate the electronic document with the signature document, where the electronic document and the signature document together comprise a signed electronic document; and

a user interface configured to receive the user input.

20. The system of claim 19, wherein the user input comprises a handwritten signature and the processor is configured to alter an appearance of the signature document based on the user input by applying a visual representation of the handwritten signature to a graphical representation of the signature document.

21. The system of claim 20, wherein the visual representation of the handwritten signature comprises a black line.

22. The system of claim 19, wherein the user input comprises biometric data and the processor is configured to alter an appearance of the signature document based on the user input by applying a visual representation of the biometric data to a graphical representation of the signature document.

23. The system of claim 22, wherein the visual representation of the biometric data comprises a black line.

24. The system of claim 19, wherein the signature document is derived from a digital image.

25. The system of claim 19, wherein the user interface comprises a touch screen.

26. The system of claim 19, wherein the one-way hash comprises a checksum.

27. The system of claim 19, wherein the processor is further configured to:

encrypt the one-way hash; and

embed a digital watermark representing the encrypted one-way hash in the signature document.

28. The system of claim 27, wherein the processor is further configured to:

encrypt the one-way hash using a private key associated with a device used to calculate the one-way hash.

29. A system comprising:

a processor configured to;

receive a signed electronic document comprising an electronic document and a signature document, the signature document including an electronic signature applied to an image and a digital watermark representing a first one-way hash embedded in the image;

obtain the first one-way hash from the image;

calculate a second one-way hash for the electronic document;

compare the first one-way hash to the second one-way hash; and

verify the signed electronic document based at least in part on the one-way hash comparison.

30. The system of claim 29, wherein the electronic signature applied to an image comprises a black line representing a handwritten signature applied to a graphical representation of an image.

31. The system of claim 30, further comprising:

the processor further configured to;

compare the electronic handwritten signature to a valid signature specimen; and

verify the signature document based at least in part on the signature comparison.

32. The system of claim 30, further comprising:

the processor further configured to;

inspect the black line for indications of alterations to the image after the black line was applied.

33. The system of claim 29, wherein the electronic signature applied to an image comprises a black line representing a password applied to a graphical representation of an image.

34. The system of claim 33, further comprising:

the processor further configured to;

compare the password to an expected password; and

verify the signature document based at least in part on the password comparison.

35. The system of claim 33, further comprising:

the processor further configured to;

inspect the black line for indications of alterations to the image after the black line was applied.

36. The system of claim 29, wherein the digital watermark represents an encrypted one-way hash, the processor further configured to:

decrypt the one-way hash; and

compare the decrypted one-way hash to the second one-way hash.

37. The system of claim 36, wherein the processor is further configured to decrypt the one-way hash using a public key associated with a device used to encrypt the one-way hash.

38. A method comprising:

calculating a one-way hash for an electronic document;

embedding a digital watermark representing the one-way hash in an audio signature file;

based on a user input, altering a sound of the audio signature file having the embedded digital watermark; and

associating the electronic document with the audio signature file, wherein the electronic document and the audio signature file together comprise a signed electronic document.

39. The method of claim 38, further comprising:

encrypting the one-way hash; and

wherein embedding a digital watermark representing the one-way hash in an audio signature file comprises embedding a digital watermark representing the encrypted one-way hash in the audio signature file.

40. The method of claim 39, wherein:

encrypting the one-way hash comprises using a private key associated with a device used to calculate the one-way hash.

41. A method comprising:

receiving a signed electronic document comprising an electronic document and an audio signature file, the audio signature file including an electronic signature applied to an audio recording and a digital watermark representing a first one-way hash embedded in the audio recording;

obtaining the first one-way hash from the audio recording;

calculating a second one-way hash for the electronic document;

comparing the first one-way hash to the second one-way hash; and

verifying the signed electronic document based at least in part on the one-way hash comparison.

42. The method of claim 41, wherein the digital watermark represents an encrypted one-way hash, the method further comprising:

decrypting the one-way hash; and

comparing the decrypted one-way hash to the second one-way hash.

43. The method of claim 42, wherein decrypting the one-way hash comprises using a public key associated with a device used to encrypt the one-way hash.

44. A computer program product, tangibly stored on a computer-readable medium, comprising instructions operable to cause a programmable processor to:

calculate a one-way hash for an electronic document;

embed a digital watermark representing the one-way hash in a signature document;

based on a user input, alter an appearance of the signature document having the embedded digital watermark; and

associate the electronic document with the signature document, wherein the electronic document and the signature document together comprise a signed electronic document.

45. The computer program product of claim 44, wherein the user input comprises a handwritten signature and instructions operable to alter an appearance of the signature document comprise instructions operable to:

apply a visual representation of the handwritten signature to a graphical representation of the signature document.

46. The computer program product of claim 45, wherein the visual representation of the handwritten signature comprises a black line.

47. The computer program product of claim 44, wherein the user input comprises biometric data and instructions operable to alter an appearance of the signature document comprise instructions operable to:

apply a visual representation of the biometric data to a graphical representation of the signature document.

48. The computer program product of claim 47, wherein the visual representation of the biometric data comprises a black line.

49. The computer program product of claim 44, wherein the signature document is derived from a digital image.

50. The computer program product of claim 44, wherein the one-way hash comprises a checksum.

51. The computer program product of claim 44, further comprising instructions operable to:

encrypt the one-way hash; and

wherein instructions operable to embed a digital watermark representing the one-way hash in a signature document comprise instructions operable to embed a digital watermark representing the encrypted one-way hash in the signature document.

52. The computer program product of claim 51, wherein:

instructions operable to encrypt the one-way hash comprise instructions operable to use a private key associated with a device used to calculate the one-way hash.

53. A computer program product, tangibly stored on a computer-readable medium, comprising instructions operable to cause a programmable processor to:

receive a signed electronic document comprising an electronic document and a signature document, the signature document including an electronic signature applied to an image and a digital watermark representing a first one-way hash embedded in the image;

obtain the first one-way hash from the image;

calculate a second one-way hash for the electronic document;

compare the first one-way hash to the second one-way hash; and

verify the signed electronic document based at least in part on the one-way hash comparison.

54. The computer program product of claim 53, wherein the electronic signature applied to an image comprises a black line representing a handwritten signature applied to a graphical representation of an image.

55. The computer program product of claim 54, further comprising instructions operable to:

compare the electronic handwritten signature to a valid signature specimen; and

verify the signature document based at least in part on the signature comparison.

56. The computer program product of claim 54, further comprising instructions operable to:

inspect the black line for indications of alterations to the image after the black line was applied.

57. The computer program product of claim 53, wherein the electronic signature applied to an image comprises a black line representing biometric data applied to a graphical representation of an image.

58. The computer program product of claim 57, further comprising instructions operable to:

compare the biometric data to expected biometric data; and

verify the signature document based at least in part on the comparison of biometric data.

59. The computer program product of claim 57, further comprising instructions operable to:

inspect the black line for indications of alterations to the image after the black line was applied.

60. The computer program product of claim 53, wherein the digital watermark represents an encrypted one-way hash, the instructions further operable to:

decrypt the one-way hash; and

compare the decrypted one-way hash to the second one-way hash.

61. The computer program product of claim 60, wherein instructions operable to decrypt the one-way hash comprise instructions operable to use a public key associated with a device used to encrypt the one-way hash.

62. A computer program product, tangibly stored on a computer-readable medium, comprising instructions operable to cause a programmable processor to:

calculate a one-way hash for an electronic document;

embed a digital watermark representing the one-way hash in an audio signature file;

based on a user input, alter a sound of the audio signature file having the embedded digital watermark; and

associate the electronic document with the audio signature file, wherein the electronic document and the audio signature file together comprise a signed electronic document.

63. The computer program product of claim 62, further comprising instructions operable to:

encrypt the one-way hash; and

wherein instructions operable to embed a digital watermark representing the one-way hash in an audio signature file comprise instructions operable to embed a digital watermark representing the encrypted one-way hash in the audio signature file.

64. The computer program product of claim 63, wherein:

instructions operable to encrypt the one-way hash comprise instructions operable to use a private key associated with a device used to calculate the one-way hash.

65. A computer program product, tangibly stored on a computer-readable medium, comprising instructions operable to cause a programmable processor to:

receive a signed electronic document comprising an electronic document and an audio signature file, the audio signature file including an electronic signature applied to an audio recording and a digital watermark representing a first one-way hash embedded in the audio recording;

obtain the first one-way hash from the audio recording;

calculate a second one-way hash for the electronic document;

compare the first one-way hash to the second one-way hash; and

verify the signed electronic document based at least in part on the one-way hash comparison.

66. The computer program product of claim 65, wherein the digital watermark represents an encrypted one-way hash, the instructions further operable to:

decrypt the one-way hash; and

compare the decrypted one-way hash to the second one-way hash.

67. The computer program product of claim 66, wherein instructions operable to decrypt the one-way hash comprise instructions operable to use a public key associated with a device used to encrypt the one-way hash.