Electronic document verification system and method

• US 5,606,609 A
• Filed: 09/19/1994
• Issued: 02/25/1997
• Est. Priority Date: 09/19/1994
• Status: Expired due to Term

• Current Assignee: Silanis Technology Inc. (OneSpan, Inc.)
• Original Assignee: Scientific-Atlanta (Cisco Systems, Inc.)
• Inventors: Adler, James M., Houser, Peter B.
• Primary Examiner(s): Cain, David C.
• Application Number:
  US08/306,447
• Time in Patent Office: 890 Days
• Field of Search: 380/23, 380/54, 380/4, 380/25
• US Class Current: 713/179
• CPC Class Codes: H04L 2209/608 Watermarking
• CPC Class Codes: H04L 9/3236 using cryptographic hash functions
• CPC Class Codes: H04L 9/3247 involving digital signatures

Abstract

The integrity or the signator of an electronic document can be verified by embedding a security object, for example, supported by an object linking and embedding (OLE) capability, in the electronic document at a location selected by the signator. The embedded security object includes security information and an identifier for invoking the processing of the security information. The security information may include a document digest that characterizes the electronic document at the time the security object was embedded, a signature digest that identifies the signator and that characterizes the instance of the embedded security object, and the signator'"'"'s electronic chop, which may be the signator'"'"'s digitized signature or other graphic image. In addition, the security information can be encrypted using either private key encryption or public key encryption. When the electronic document is later displayed, the identifier invokes processing that decrypts the security information and calculates the document digest based on the current state of the electronic document. The signator of the electronic document can be verified based upon the result of the decryption. The integrity of the electronic document can be verified if the decrypted document digest matches the calculated document digest. If the signator and the document integrity are confirmed, the electronic chop is displayed in the document. If, however, the signator or document integrity are not verified, the electronic chop is not displayed. In addition, a warning message may be displayed if verification fails.

Claims

1. An apparatus for embedding select information in an electronic document, comprising:

an information assembler, responsive to a user'"'"'s request, for assembling said select information into a predetermined format; and

an object embedder for embedding said select information and information for invoking a predetermined application for processing said select information in an electronic document.

2. The apparatus according to claim 1, wherein said select information includes an electronic chop associated with the user.

3. The apparatus according to claim 1, further comprising an encrypter for encrypting the select information.

4. The apparatus according to claim 3, wherein said encrypter encrypts the select information using private key encryption.

5. The apparatus according to claim 3, wherein said encrypter encrypts the select information using public key encryption.

6. The apparatus according to claim 1, wherein said information assembler comprises a calculator for calculating a data item that characterizes the current state of the electronic document, wherein said select information includes said data item.

7. The apparatus according to claim 6, wherein said data item comprises a hash value of the electronic document.

8. The apparatus according to claim 6, wherein said electronic document comprises a text portion including character information and a code portion for controlling a presentation of the character information, and wherein said data item comprises a data item that characterizes the text portion of said electronic document.

9. The apparatus according to claim 1, further comprising a serial number generator, and wherein said select information includes said serial number.

10. The apparatus according to claim 1, wherein said select information comprises a public key-encrypted value indicative of said apparatus for embedding the information in the electronic document.

11. The apparatus according to claim 1, wherein said object embedder is an OLE object embedder.

12. The apparatus according to claim 1, wherein said information for invoking a predetermined application for processing said select information comprises an identifier that identifies the predetermined application.

13. The apparatus according to claim 1, wherein said object embedder embeds said select information and information for invoking processing of said select information in the electronic document at a location selected by the user.

65. The apparatus according to claim 1, wherein said select information includes security information.

14. An embedded object interpreter for verification of an electronic document, comprising:

an information extractor, responsive to an embedded object in an electronic document, for extracting select information from the embedded object; and

a verification processor for verifying an aspect of said electronic document using said extracted select information.

15. The embedded object interpreter according to claim 14, wherein the select information includes an electronic chop associated with a party that caused the select information to be embedded in the electronic document, and said embedded object interpreter further comprises:

a display controller for controlling a display device to display the electronic chop in said electronic document only if said verification processor verifies said aspect of said electronic document.

16. The embedded object interpreter according to claim 15, further comprising a watermark generator for generating a watermark graphic, wherein said display controller, responsive to said watermark generator, controls the display device to display the electronic chop superimposed on said watermark graphic if said verification processor verifies said aspect of said electronic document.

17. The embedded object interpreter according to claim 16, wherein the watermark generator generates the watermark graphic using the extracted select information.

18. The embedded object interpreter according to claim 17, wherein the watermark graphic comprises a time-dependent watermark graphic.

19. The embedded object interpreter according to claim 18, wherein the time-dependent watermark graphic is predictable from the extracted select information and appears random.

20. The embedded object interpreter according to claim 14, further comprising a decrypter for decrypting the extracted select information.

21. The embedded object interpreter according to claim 20, wherein said decrypter decrypts said extracted select information using a private key.

22. The embedded object interpreter according to claim 20, wherein said decrypter decrypts said extracted select information using a public key.

23. The embedded object interpreter according to claim 14, wherein said extracted select information includes a value indicative of an object embedder used to embed the embedded object in the electronic document, and wherein said verification processor verifies the authenticity of the object embedder.

24. The embedded object interpreter according to claim 14, wherein said extracted select information comprises an extracted document digest including an extracted data item that characterizes the content of the electronic document at the time that the select information was embedded, and wherein said verification processor verifies electronic document integrity using the extracted document digest.

25. The embedded object interpreter according to claims 24, wherein said verification processor comprises:

a calculator for calculating a data item that characterizes a current content of the electronic document, said calculated data item corresponding to the extracted data item;

a comparator for comparing the extracted data item with the calculated data item; and

a verification detector, responsive to said comparator, for detecting that said electronic document was modified if said extracted data item does not match said calculated data item and for detecting that said electronic document was not modified if said extracted data item matches said calculated data item.

26. The embedded object interpreter according to claims 25, wherein said extracted data item comprises an extracted hash value and said calculator calculates a hash value using the electronic document.

27. The embedded object interpreter according to claim 26, wherein the select information includes an electronic chop associated with a party that caused the select information to be embedded in the electronic document, and said embedded object interpreter further comprises:

a display controller for controlling a display device to display the electronic chop in said electronic document only if said verification detector detects that said electronic document was not modified.

28. The embedded object interpreter according to claim 27, further comprising a watermark generator for generating a watermark graphic, wherein said display controller, responsive to said watermark generator, controls the display device to display the electronic chop superimposed on said watermark graphic if said verification detector detects that said electronic document was not modified.

29. The embedded object interpreter according to claim 14, wherein said extracted select information includes an extracted serial number and said verification processor verifies the identity of the party that caused the select information to be embedded in said electronic document by comparing said extracted serial number to a stored serial number.

30. The embedded object interpreter according to claim 29, wherein the select information includes an electronic chop associated with a party that caused the select information to be embedded in the electronic document, said embedded object interpreter further comprising:

a display controller for controlling a display device to display the electronic chop in said electronic document only if said verification processor verifies the identity of the party that caused the select information to be embedded in said electronic document.

31. The embedded object interpreter according to claim 30, further comprising a watermark generator for generating a watermark graphic, wherein said display controller, responsive to said watermark generator, controls the display device to display the electronic chop superimposed on said watermark graphic if said verification processor verifies the identity of the party that caused the select information to be embedded in said electronic document.

66. The embedded object interpreter according to claim 14, wherein said select information includes security information.

32. An electronic document verification system, comprising:

an information assembler, responsive to a user'"'"'s request, for assembling select information into a predetermined format;

an object embedder for embedding an object into a target electronic document at a location selected by the user, wherein the embedded object includes the assembled select information and an identifier for invoking processing of the select information;

an embedded information extractor, responsive to an embedded object in a signed electronic document, for extracting select information from the embedded object; and

a verification processor for processing said extracted select information to verify an aspect of said signed electronic document.

33. The electronic document verification system according to claim 32, further comprising:

an encrypter for encrypting the assembled select information; and

a decrypter for decrypting the extracted select information.

34. The electronic document verification system according to claim 33, wherein said encrypter encrypts the assembled select information using public key encryption and said decrypter decrypts said extracted select information using public key decryption.

35. The electronic document verification system according to claim 33, wherein said encrypter encrypts the assembled select information using private key encryption and said decrypter decrypts said extracted select information using private key decryption.

36. The electronic document verification system according to claim 32, wherein:

said information assembler comprises a first hash value calculator for calculating a hash value of the target electronic document, wherein the hash value is included in said assembled select information; and

said verification processor comprises a second hash value calculator for calculating a hash value of the signed document, a comparator for comparing the calculated hash value with a hash value in the extracted select information, and a verification detector, responsive to said comparator, for detecting that the signed electronic document was modified if the calculated hash value differs from the hash value in the extracted select information and for detecting that the signed electronic document was not modified if the calculated hash value matches the hash value in the extracted select information.

37. The electronic document verification system according to claim 32, further comprising:

a serial number generator for generating a serial number associated with the instance of the users request, wherein said information assembler includes the serial number in the select information; and

a memory for storing said select information assembled by said information assembler, including the serial number,

wherein said verification processor comprises a comparator for comparing a serial number in the extracted select information with the stored serial number and a verification detector for detecting that the signed electronic document is authentic if said stored serial number matches the serial number in the extracted select information and for detecting that the signed electronic document is not authentic if the stored serial number does not match the serial number in the extracted select information.

38. The electronic document verification system according to claim 32, wherein said extracted select information includes an electronic chop, and further comprising:

a display controller for controlling a display device to display the electronic chop in the signed electronic document only if said verification processor verifies said aspect of said signed electronic document.

39. The electronic document verification system according to claim 38, further comprising a watermark generator for generating a watermark graphic, wherein said display controller, responsive to said watermark generator, controls the display device to display the electronic chop superimposed on said watermark graphic if said verification processor verifies said aspect of said signed electronic document.

40. The electronic document verification system according to claim 39, wherein the watermark generator generates the watermark graphic using the extracted select information.

41. The electronic document verification system according to claim 40, wherein the watermark graphic comprises a time-dependent watermark graphic.

42. The embedded object interpreter according to claim 41, wherein the time-dependent watermark graphic is predictable from the extracted select information and appears random.

67. The electronic document verification system according to claim 32, wherein said select information includes security information.

43. An electronic document verification method for verifying the integrity of an electronic document having an object embedded therein, the embedded object including a document digest, said document digest including a data item indicative of the content of the electronic document at the time that the embedded object was embedded and chop graphics information associated with a party that caused the embedded object to be embedded in the electronic document, said electronic verification method comprising the steps of:

extracting the document digest and the chop graphics information form the embedded object;

calculating a data item indicative of a current content of the electronic document;

displaying the chop graphics data in the electronic document if the data item in the extracted document digest matches the calculated data item and displaying the electronic document without the chop graphics data if the data item in the extracted document digest does not match the calculated data item.

44. The method according to claim 43, wherein the document digest and the chop graphics data in said embedded object are encrypted, and said method further comprises the step of:

decrypting the extracted document digest and extracted chop graphics information.

45. The method according to claim 44, wherein said step of decrypting comprises decrypting the extracted document digest and the extracted chop graphics information using a private key.

46. The method according to claim 44, wherein said step of decrypting comprises decrypting the extracted document digest and the extracted chop graphics information using a public key.

47. The method according to claim 43, wherein the data item in the document digest comprises a hash value, and wherein said step of calculating comprises calculating a hash value based on the current content of the electronic document.

48. The method according to claim 43, wherein said step of displaying further comprises displaying a warning message in the electronic document if the data item in the extracted document digest does not match the calculated data item.

68. The method according to claim 43, wherein said embedded object includes security information.

49. An electronic document verification system, comprising:

a verification processor for verifying an aspect of an electronic document approved by a signator; and

an indication controller for presenting a chop graphic associated with the signator in the electronic document only if said verification processor verifies said aspect of said electronic document, wherein the chop graphic is omitted from said electronic document if said verification processor contradicts said aspect of said electronic document.

50. The electronic document verification system according to claim 49, wherein said electronic document is displayed on a display and said indication controller controls the display to display a video chop graphic associated with the signator in the displayed electronic document only if said verification processor verifies said aspect of said electronic document.

51. The electronic document verification system according to claim 50, further comprising an electronic watermark generator for generating an electronic watermark and for supplying the electronic watermark to said indication controller, wherein the electronic watermark generates a video watermark when displayed and wherein said indication controller controls the display to display the video chop graphic superimposed over the video watermark in the displayed electronic document only if said verification processor verifies said aspect of said electronic document.

52. The electronic document verification system according to claim 51, wherein said electronic watermark comprises information related to the signator and the electronic document.

53. The electronic document verification system according to claim 51, wherein said electronic watermark comprises a time-varying icon.

54. The embedded object interpreter according to claim 53, wherein the time-dependent watermark graphic is predictable from the extracted security information and appears random.

55. The electronic-document verification system according to claim 50, wherein said electronic document is printed using a printer and said indication controller controls the printer to print a printed chop graphic associated with the signator in the printed electronic document only if said verification processor verifies said aspect of said electronic document.

56. The electronic document verification system according to claim 51, further comprising an electronic watermark generator for generating an electronic watermark and for supplying the electronic watermark to said indication controller, wherein the electronic watermark generates a printed watermark when received by the printer and wherein said indication controller controls the printer to print the printed chop graphic superimposed over the printed watermark in the printed electronic document only if said verification processor verifies said aspect of said electronic document.

57. The electronic document verification system according to claim 52, wherein said electronic watermark comprises information related to the signator and the electronic document.

58. The electronic document verification system according to claim 57, wherein said printed watermark comprises the information related to the signator and the electronic document in a small font so as to appear substantially as a gray area.

59. The electronic document verification system according to claim 57, wherein said printed watermark comprises the information formatted randomly to thereby inhibit subsequent modification.

60. A verification system comprising:

an electronic watermark generator for generating a watermark icon that varies chaotically in time from a set of initial states; and

a display controller for displaying the watermark icon on a display.

61. The verification system according to claim 60, wherein said electronic watermark generator generates a watermark icon that varies chaotically in discrete stages.

62. The verification system according to claim 61, wherein said watermark icon comprises a clock icon having at least an hour hand and a minute hand that varies chaotically in discrete stages.

63. The verification system according to claim 60, wherein said electronic watermark generator generates a watermark icon that varies in accordance with a Lorenz system.

64. The verification system according to claim 63, wherein said watermark icon comprises a clock icon having at least an hour hand and a minute hand that varies chaotically in discrete stages according to the Lorenz system.