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Document modification detection and prevention

  • US 8,533,480 B2
  • Filed: 06/07/2010
  • Issued: 09/10/2013
  • Est. Priority Date: 05/16/2003
  • Status: Active Grant
First Claim
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1. A computer-implemented method comprising:

  • receiving, by a computing device processor, an electronic document including content items, a rule and a digital signature, wherein the rule specifies what parts of the electronic document are allowed to change based on user interaction with the electronic document;

    generating a digest for the electronic document by digesting all of the content items, using multiple functions based upon complexity of the content items, except for at least a first content item that is ignored in the digestion based on the rule;

    comparing the generated digest with a stored digest that is associated with the electronic document; and

    invalidating the digital signature if the generated digest indicates a difference in any of the digested content items,wherein if the generated digest indicates no difference in any of the digested content items, the method further comprises;

    subsequently receiving a user input attempting to create a new state of the received electronic document;

    determining whether the user input is allowed by the rule; and

    invalidating the digital signature if the user input is not allowed by the rule, andwherein the rule applies differently to a first author and a second author, such that the user input causes a first digital signature of the first author to be invalidated but does not cause a second digital signature of the second author to be invalidated.

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