Patent ID: 7502934
Filing Date: 2009-03-10
Classification: G06F,H04L

Abstract:
1. A method comprising: receiving a signed electronic document comprising an electronic document and a signature document, the signature document including an electronic handwritten signature applied to first image and a digital watermark, wherein the digital watermark is a second image representing a watermark that overlays at least a portion of the first image and embeds in the signature document a first one-way hash calculated using the electronic document, and where the applied electronic signature altered an appearance of the signature document; verifying an integrity of the digital watermark based, at least in part, on an integrity of the electronic handwritten signature applied to the image; obtaining the first one-way hash from the first image in connection with at least determining the integrity of the digital watermark; calculating a second one-way hash for the electronic document; comparing the first one-way hash to the second one-way hash; and verifying by a receiving device contents of the signed electronic document based at least in part on the one-way hash comparison.