Patent ID: 8595503

Claim:
A document authentication method comprising: (a) obtaining a first digital document; (b) generating a second digital document from the first digital document, including: (b1) segmenting the first digital document to extract at least one segment containing critical content and at least one segment containing a non-critical image, the non-critical image including a plurality of pixels; (b2) processing the critical content to generate a bit string of processed data; (b3) modifying the non-critical image to embed the bit string in it, wherein each data bit of the bit string is embedded into predetermined low bits of one or more pixels of the modified non-critical image; (b4) calculating a hash code from the bit string of processed data using a hash function; and (b5) encoding the hash code in barcode; wherein the second digital document includes the segment containing the critical content, the segment containing the non-critical image which has been modified, and the barcode; (c) printing the second digital document to produce a printed document; (d) scanning the printed document to generate a third digital document; (e) analyzing the third digital document to determine whether it is authentic, including: (e1) segmenting the third digital document to extract at least the segment containing the critical content and the segment containing the non-critical image which has been modified; (e2) recovering the bit string embedded in the non-critical image; (e3) processing the recovered bit string to obtain re-generated critical content; (e4) comparing the re-generated critical content with the critical content obtained in step (e1) to determined whether they are substantially identical, wherein if they are not substantially identical, the third digital document is determined to be not authentic; (e5) identifying the barcode in the third digital document and extracting the hash code encoded therein; (e6) obtaining a hash code from the recovered bit string; and (e7) comparing the hash code obtained in step (e6) with the hash code extracted from the barcode to determine if they are identical, wherein if they are not identical, the third digital document is determined to be not authentic; and (f) displaying or storing a result indicating whether the third digital document is authentic.