Document modification detection and prevention

• US 20040230891A1
• Filed: 05/16/2003
• Published: 11/18/2004
• Est. Priority Date: 05/16/2003
• Status: Active Grant

• Current Assignee: Adobe Inc.
• Original Assignee: Adobe Systems Incorporated (Adobe Inc.)
• Inventors: Agrawal, Sunil C., Pravetz, James D., Chaudhury, Krish
• Granted Patent: US 7,735,144 B2
• Time in Patent Office: Days
• US Class Current: 715/511
• CPC Class Codes: G06F 21/6218 to a system of files or objects, e.g. local or distributed file system or database
• CPC Class Codes: H04L 63/18 using different networks or channels, e.g. using out of band channels cryptographic mechanisms or cryptographic arrangements for key distribution involving distinctive intermediate devices or communication paths H04L9/0827; cryptographic mechanisms or cryptographic arrangements for authentication using a plurality of channels H04L9/3215
• CPC Class Codes: H04L 9/3247 involving digital signatures

Abstract

Methods and apparatus, including computer program products, implementing and using techniques for document authentication. An electronic document is presented to a user. The electronic document has data representing a signed state and a current state. A disallowed difference between the signed state and the current state is detected, based on one or more rules that are associated with the electronic document. A digital signature associated with the electronic document is invalidated in response to the detecting.

Claims

1. A computer-implemented method, comprising:

presenting an electronic document to a user, the electronic document having data representing a signed state and a current state;

detecting an unauthorized difference between the signed state and the current state, based on one or more rules that are associated with the electronic document; and

invalidating a digital signature associated with the electronic document in response to the detecting.

2. The method of claim 1, further comprising:

presenting the signed state of the electronic document to the user.

3. The method of claim 1, wherein:

the electronic document includes an object hash representing the signed state of the electronic document, the object hash being generated subject to the rules that are associated with the electronic document.

4. The method of claim 3, wherein:

the object hash is based on content items of the electronic document that are invariant to a set of one or more operations authorized by the rules associated with the electronic document.

5. The method of claim 4, wherein:

the set of one or more operations is authorized by an author providing the signed state of the electronic document.

6. The method of claim 3, wherein detecting a difference includes:

generating an object hash of the current state according to a set of rules associated with the signed state of the electronic document; and

comparing the generated object hash with the object hash in the electronic document.

7. The method of claim 3, wherein:

the electronic document includes a byte range hash.

8. The method of claim 7, wherein detecting a difference includes:

generating a byte range hash according to a saved version of the electronic document; and

comparing the generated byte range hash with the byte range hash in the electronic document.

9. The method of claim 1, wherein:

the difference between the signed state and the current state relates to one or more of the following operations performed on data in the electronic document;

digitally signing the electronic document, entering data into predefined fields of the electronic document, and annotating the electronic document.

10. The method of claim 1, further comprising:

receiving an input defining a second signed state; and

detecting a difference between the second signed state and the current state.

11. The method of claim 10 further comprising:

invalidating a digital signature relating to the second signed state if the detected difference between the current state and the second signed state represents a difference that is not permitted by the rules associated with the electronic document.

12. The method of claim 1, further comprising:

validating a digital signature associated with the electronic document prior to detecting a difference.

13. The method of claim 1, wherein invalidating the digital signature comprises:

invalidating the digital signature if the detected difference between the current state and the signed state represents a difference that is not permitted by an author providing the digital signature.

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

present an electronic document to a user, the electronic document having data representing a signed state and a current state;

detect an unauthorized difference between the signed state and the current state, based on one or more rules that are associated with the electronic document; and

invalidate a digital signature associated with the electronic document in response to the detecting.

15. The computer program product of claim 14, further comprising instructions to:

present the signed state of the electronic document to the user.

16. The computer program product of claim 14, wherein:

the electronic document includes an object hash representing the signed state of the electronic document, the object hash being generated subject to the rules that are associated with the electronic document.

17. The computer program product of claim 16, wherein:

the object hash is based on content items of the electronic document that are invariant to a set of one or more operations authorized by the rules associated with the electronic document.

18. The computer program product of claim 17, wherein:

the set of one or more operations is authorized by an author providing the signed state of the electronic document.

19. The computer program product of claim 16, wherein the instructions to detect a difference include instructions to:

generate an object hash of the current state according to a set of rules associated with the signed state of the electronic document; and

compare the generated object hash with the object hash in the electronic document.

20. The computer program product of claim 16, wherein:

the electronic document includes a byte range hash.

21. The computer program product of claim 16, wherein the instructions to detect a difference include instructions to:

generate a byte range hash according to a saved version of the electronic document; and

compare the generated byte range hash with the byte range hash in the electronic document.

22. The computer program product of claim 14, wherein:

the difference between the signed state and the current state relates to one or more of the following operations performed on data in the electronic document;

digitally signing the electronic document, entering data into predefined fields of the electronic document, and annotating the electronic document.

23. The computer program product of claim 14, further comprising instructions to:

receive an input defining a second signed state; and

detect a difference between the second signed state and the current state.

24. The computer program product of claim 23, further comprising instructions to:

invalidate a digital signature relating to the second signed state if the detected difference between the current state and the second signed state represents a difference that is not permitted by the rules associated with the electronic document.

25. The computer program product of claim 14, further comprising instructions to:

validate a digital signature associated with the electronic document prior to detecting a difference.

26. The computer program product of claim 14, further comprising instructions to:

invalidate the digital signature if the detected difference between the current state and the signed state represents a difference that is not permitted by an author providing the digital signature.