Patent Document ID: 8181850
Application ID: 12939423

Base Claim:
1. A method of authenticating a first document including content and a barcode, said barcode comprising barcode elements each having a predetermined form, said method comprising the steps of: detecting a plurality of the barcode elements of the barcode in a representation of the first document; determining a visual difference between each of the detected barcode elements and the predetermined form of the barcode element; decoding the barcode to determine a second document; and comparing the first document and the second document based on the determined visual difference, in order to authenticate the first document, wherein at least the determining and decoding steps are implemented using a processor.

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Claim 7:
7. The method of claim 1 , wherein the visual difference is determined by estimating one or more of a point spread function (PSF) for the detected plurality of barcode elements, higher order image moments for the detected plurality of barcode elements, non-linear dot gain for the detected plurality of barcode elements, a change in contrast in the detected plurality of barcode elements, a change in gamma in the detected plurality of barcode elements, and a change in brightness in the detected plurality of barcode elements, and wherein the method further comprises the step of convolving the PSF with the content of the second document.