Methods for encoding security documents
First Claim
1. A substrate having a pattern formed over at least a portion thereof, characterized in that the pattern has a substantially uniform visible appearance to casual human inspection, but the pattern marks the substrate to include N-bits of digital data, where N is greater than one, said N-bits being detectable through computer analysis from visible light scan data corresponding to said substrate, but wherein the marking is not apparent through human inspection of the document.
6 Assignments
0 Petitions
Accused Products
Abstract
Line art on a banknote or other security document is slightly changed to effect the encoding of plural-bit digital data (i.e. the banknote is digitally watermarked). When such a banknote is thereafter scanned, the resulting image data can be recognized as corresponding to a banknote by detection of the encoded data. (Alternatively, the image data can be recognized as corresponding to a banknote by machine detection of other forms of watermarking, or by reference to visible structures characteristic of banknotes.) In response to detection of a banknote, the detecting apparatus (e.g., a scanner, photocopier, or printer) can intervene so as to prevent or deter counterfeiting. For example, the apparatus can interrupt a copying operation, and display a message reminding the operator that it is illegal to reproduce currency. Another option is to dial a remote service and report the attempted reproduction of a banknote. Yet another option is to permit the copying, but to insert forensic tracer data (e.g. steganographically encoded binary data) in the resultant copy. The tracer data can memorialize the serial number of the machine that made the copy and/or the date and time the copy was made. To address privacy concerns, such tracer data is not normally inserted in photocopied output, but is so inserted only when the subject being photocopied is detected as being a banknote.
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Citations
11 Claims
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1. A substrate having a pattern formed over at least a portion thereof, characterized in that the pattern has a substantially uniform visible appearance to casual human inspection, but the pattern marks the substrate to include N-bits of digital data, where N is greater than one, said N-bits being detectable through computer analysis from visible light scan data corresponding to said substrate, but wherein the marking is not apparent through human inspection of the document.
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2. A check formed on the substrate of claim 2.
- 3. A method of marking a check to convey plural binary bits, thereby facilitating machine-recognition thereof, the check having a visible structure formed thereon, the method being characterized in that the marking is not apparent to human observers of the document, yet can be detected from image data generated by visible light scanning of said check.
- 6. A method of marking a security document to convey plural bit information, thereby facilitating machine-recognition thereof through detection of image data generated by visible light scanning of the security document, the marking including a visible pattern formed over at least a portion of the security document, wherein the pattern does not betray the existence of the plural bit information to casual human observers of the document.
Specification