Document digest allowing selective changes to a document

• US 8,660,960 B2
• Filed: 11/27/2002
• Issued: 02/25/2014
• Est. Priority Date: 11/27/2002
• Status: Active Grant

• Current Assignee: Adobe Inc.
• Original Assignee: Adobe Systems Incorporated (Adobe Inc.)
• Inventors: Chaudhury, Krish, Pravetz, James D.
• Primary Examiner(s): Augustin, Evens J
• Application Number:
  US10/306,779
• Publication Number:
  US 20130219451A1
• Time in Patent Office: 4,108 Days
• Field of Search: 707/9, 715/530, 713/176, 705/51
• US Class Current: 705/51
• CPC Class Codes: G06F 21/10 Protecting distributed programs or content, e.g. vending or licensing of copyrighted material protection in video systems or pay television H04N7/16 ; Digital rights management [DRM]
• CPC Class Codes: G06F 21/60 Protecting data

Abstract

Methods and apparatus, including computer program products, implementing and using techniques for digital rights management. A set of content items is defined in an electronic document based on a set of rules. The rules in the set of rules are associated with one or more operations that can be performed on content items in the electronic document. The set of content items include only content items that are invariant to the operations associated with the rules in the set of rules. A representation of the content items in the set of content items is generated. An electronic document is also described.

Claims

1. A computer-implemented method comprising:

receiving, by an electronic document reader, an electronic document that includes (a) a plurality of content items, (b) a set of rules that defines a set of allowed operations which are authorized to be performed on the plurality of content items included in the electronic document, and (c) a first selective digest generated by a document author;

identifying, by a processor, one or more invariant content items from amongst the plurality of content items, wherein the invariant content items remain unchanged when the set of allowed operations are performed on the plurality of content items included in the electronic document;

generating, by the processor, a second selective digest of the one or more invariant content items;

performing, by the processor, a comparison of the first selective digest generated by the document author and the second selective digest generated by the processor, wherein the comparison results in validation information;

disabling, by the electronic document reader, the allowed operations when the comparison of the first and second selective digests indicates that operations have been performed on the electronic document which are not allowed under the set of rules; and

saving, on a computer readable storage device, a version of the electronic document that includes the set of rules and the validation information.

2. The method of claim 1, wherein the second selective digest is represented as a hash having a lower layer containing functionality for digesting a basic content item, an intermediate layer containing functionality for digesting a semi-complex content item, and an upper layer containing functionality for digesting a complex content item.

3. The method of claim 1, wherein the second selective digest is represented as a hash having a lower layer containing functionality for digesting a basic content item that consists of a string, an intermediate layer containing functionality for digesting a semi-complex content item that consists of an annotation, and an upper layer containing functionality for digesting a complex content item that consists of a page.

4. The method of claim 1, wherein disabling the allowed operations further comprises providing, by the electronic document reader, an error message indicating that an unauthorized operation has been performed.

5. The method of claim 1, further comprising receiving, by the electronic document reader, user input that defines the set of rules.

6. The method of claim 1, wherein the set of allowed operations includes an operation selected from the group consisting of a form fill-in operation, a signature field signing operation, and an annotation operation.

7. The method of claim 1, wherein the set of allowed operations does not include an annotation operation.

8. The method of claim 1, wherein the one or more invariant content items includes a content item selected from the group consisting of an annotation region, a text label, an annotation flag, and an appearance state.

9. A system for validating an electronic document, the system comprising:

one or more processors;

an electronic document reader; and

a non-transient computer-readable medium having an electronic document stored thereon, the electronic document comprising;

a plurality of content items including one or more invariant content items;

a set of rules that defines a set of allowed operations which are authorized to be performed on the plurality of content items by the electronic document reader, wherein performing the allowed operations does not result in any changes being made to the one or more invariant content items;

a first selective digest that is generated by a document author based on a first digesting of the one or more invariant content items;

validation information that results from a comparison of the first selective digest and a second selective digest that is generated by the one or more processors based on a subsequent digesting of the one or more invariant content items, wherein the validation information indicates whether operations have been performed on the electronic document which are not allowed under the set of rules; and

instructions configured to cause the electronic document reader to disable the allowed operations when the comparison of the first and second selective digests indicates that operations have been performed on the electronic document which are not allowed under the set of rules.

10. The system of claim 9, wherein the second selective digest is represented as a hash having a lower layer containing functionality for digesting a basic content item that consists of a string, an intermediate layer containing functionality for digesting a semi-complex content item that consists of an annotation, and an upper layer containing functionality for digesting a complex content item that consists of a page.

11. The system of claim 9, wherein one or more of the rules in the set of rules are associated with an operation selected from the group consisting of a form fill-in operation, a signature field signing operation, and an annotation operation.

12. The system of claim 9, wherein the set of allowed operations does not include an annotation operation.

13. The system of claim 9, wherein the one or more invariant content items includes a content item selected from the group consisting of an annotation region, a text label, an annotation flag, and an appearance state.

14. A non-transient machine-readable medium having instructions encoded thereon that, when executed by a processor, causes an electronic document validation process to be carried out, the process comprising:

receiving, by an electronic document reader, an electronic document that includes (a) a plurality of content items, (b) a set of rules that defines a set of allowed operations which are authorized to be performed on the plurality of content items included in the electronic document, and (c) a first selective digest generated by a document author;

identifying, by the processor, one or more invariant content items from amongst the plurality of content items, wherein the invariant content items remain unchanged when the set of allowed operations are performed on the plurality of content items included in the electronic document;

generating, by the processor, a second selective digest of the one or more invariant content items;

performing, by the processor, a comparison of the first selective digest generated by the document author and the second selective digest generated by the processor, wherein the comparison results in validation information;

disabling, by the electronic document reader, the allowed operations when the comparison of the first and second selective digests indicates that operations have been performed on the electronic document which are not allowed under the set of rules; and

saving, on a computer readable storage device, a version of the electronic document that includes the set of rules and the validation information.

15. The non-transient computer-readable medium of claim 14, wherein disabling the allowed operations further comprises providing an error message indicating that an unauthorized operation has been performed.

16. The electronic document reader of claim 14, wherein the process further comprises receiving user input that defines the set of rules.

17. The non-transient computer-readable medium of claim 14, wherein the second selective digest is generated based on all of the invariant content items identified from amongst the plurality of content items.

18. The non-transient computer-readable medium of claim 14, wherein the second selective digest is generated by recursively digesting the one or more invariant content items.

19. The non-transient computer-readable medium of claim 14, wherein the second selective digest is represented as a hash having a lower layer containing functionality for digesting a basic content item, an intermediate layer containing functionality for digesting a semi-complex content item, and an upper layer containing functionality for digesting a complex content item.

20. The non-transient computer-readable medium of claim 14, wherein the set of allowed operations includes an operation selected from the group consisting of a form fill-in operation, a signature field signing operation, and an annotation operation.