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Product and Document Security Method

Utilizing microdrop combinatorics, ink set and ink composition used therein, and products formed

SLAC National Accelerator Laboratory

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Technology Marketing SummaryResearchers at the Stanford Linear Accelerator Center have invented a patented, inexpensive security method for uniquely marking and identifying of physical objects (such as documents or labels). This technology uses the mixing of inks in numerous different ratios in printing arbitrary marks on a given object. The ink mixture used in a printed mark produces a unique, nonlinear spectral response or pattern upon its optical excitation. This spectral pattern can then be easily measured for authentication of the object, but cannot be replicated by a counterfeiter without a specific information key, which is knowledge of exactly what inks are used and what their original mixing ratios are. As such, a truly hard-to-break cryptographic approach in a document security method is simply implemented.

The basic method can be implemented with low-cost hardware - a computer, a specialized inkjet printer, and an optical reader - to create unique security labels for individual items, and is scalable for both low and high security applications. The invention has a wide variety of applications, including legal and financial documents, consumer goods, food and drug labeling, entertainment tickets, and access control cards.DescriptionThis technology implements trap-door printing on a substrate with combinatorial microdrop arrays to form arbitrary patterns on the substrate as a means to authenticate products and documents.
One method of implementing difficult reversibility in the printing and readout relationship utilizes the combination of pigments and phosphors having non-additive color mixing characteristics to make colored microdots.  These microdots are produced by microdroppers or inkjet ejectors, each having a certain proportion of pigments and, therefore, would be producing a unique spectral response.  Creating and characterizing a microdot having a unique spectral response holds the “cryptographic key.”  A re-measurement of the spectral response of a microdot that matches the “key” authenticates the document on which the microdot is placed.

Without knowledge of the “key” and because of the non-additive color mixing characteristics of pigments behind a microdot’s spectral response, a counterfeiter, taking the spectral measurement of a microdot from an original document, and then attempting to determine from this spectral information what pigments and what proportions of each were used to make this microdot, will find it very difficult, indeed almost impossible, to replicate an illegitimate copy of the document.  Furthermore, utilizing computer controlled microdrop or inkjet technology adds additional layers of security.  The first is that the very small amount of material used for each microdot precludes easy, direct chemical analysis of the deposited microdots.  The second security factor is that microdrop or inkjet technology can be used to create very dense two-dimensional arrays of up to tens of thousands of microdots.  This means that the reverse engineering to identify the “key” to a multi-thousand element array is an intractably difficult problem in nonlinear combinatorial chemistry.  Furthermore, printing marks at “secret” locations on a document—that can be a certain “secret” collection of marks on a document or “secret” marks that are integrated into other patterns or letter prints on a document—adds an extra  layer of security.
Benefits Low-cost:
  • Consumer-grade hardware could be used to print secure documents
  • Economically practical to print and have archived unique security labels for each individual item
Highly resistant to counterfeiting:
  • Duplication of security pattern is dependent on access to the information key
  • Resistant to compromise by thefts of raw materials
  • Allows for direct printing on objects to remove the risk of label transfer
  • Difficult to replicate spectral pattern
  • For both low and high security applications
  • Can be combined with conventional security printing methods to further enhance security
  • Easy authentication - potentially low cost optical reader, combined with verification of patterns over the internet can allow the average consumer or employee to check
Applications and IndustriesDocument security - unique marking and identification of legal and financial documents
Consumer goods authentication - for trademarked products, copyrighted content (e.g. music, video, and software), food labels, drugs
Card verification - such as access badges and credit cards
Entertainment tickets
More InformationPatent Issued: 6,786,954 (USA)Technology Status
Development StageAvailabilityPublishedLast Updated

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To: Patrick C. Lui<>