Patent ID: 7711140

Claim:
A method for processing N-level source information to determine if tampering has taken place, the method comprising the steps of: (a) resolving, in regard to an N-level image of the source information to be recorded, at least one pixel of the image into a major component having N possible values, (b) selecting a pattern element from at least one predetermined pattern, said selection depending upon (ai) the major component and (aii) the position of the at least one pixel in the image; (c) recording the selected pattern element for said at least one pixel onto a transfer medium to thereby form a secure document; (d) extracting, from the recorded secure document, a retrieved pattern element for said at least one pixel; (e) determining a pattern element depending upon (di) a major component extracted from said retrieved pattern element and (dii) the position of the at least one pixel on the recorded document; and (f) comparing the retrieved pattern element and the determined pattern element to thereby determine if the secure document has been tampered with, wherein at least said determining step and said comparing step are performed by a processor.