Patent ID: 7986806

Claim:
A method comprising: steganographically encoding, using at least a processor of a computer system, plural-bit auxiliary data onto a substrate at a specific location out of a plurality of distinct locations on the substrate, wherein the plural-bit auxiliary data is based at least in part on the specific location, wherein the plural-bit auxiliary data is substantially imperceptible to casual human inspection, but is detectable through normal ambient visible light imaging of the substrate without use of non-visible light lenses or filters, wherein the plural-bit auxiliary data is encoded such that decoding of the plural-bit auxiliary data relies on a Fourier transform that produces data in which scale and rotation can be ignored, and wherein the plural-bit auxiliary data comprises or links to information regarding use of an electronic version of a document that is placed onto the substrate; and storing, in a memory of the computer system, at least a portion of the plural-bit auxiliary data in association with data identifying a location at which the electronic version of the document is stored.