Forensic feature for secure documents

Abstract

A forensic feature for a secure document comprises a base document layer and a covert material applied to the base document layer. The covert material includes a carrier and forensic material within the carrier. The forensic material includes a ratio of salts or oxides of metals, such as rare earth metals. The ratio is selected to correspond with a source of the document. The forensic material may be mixed into a coating or ink that is applied at predetermined locations on a secure document. The ratio is then measurable from metal ion signals of the salts or oxides. This ratio, or some metric derived from it, may be linked with information embedded elsewhere in the document to enable verification of the document. Another forensic document feature has a forensic metric that is measurable from a covert material in the document, and this forensic metric corresponds to a source of the document. A blocking layer applied over the covert material prevents access to the covert material such that at least partial destruction of the document is required to measure the forensic metric. The blocking layer may have a blocking property that blocks electromagnetic waves from activating the covert material, or blocks the electromagnetic waves from the covert material in response to the activating waves. The blocking layer is deconstructed to access the forensic feature, verify the document and perform forensic tracking.

Claims

1. A method of making a forensic feature for a document comprising: providing a base document layer of a document; applying a covert material to a portion of the base document layer, the covert material including a carrier and a mixture of forensic materials within the carrier, the mixture of forensic materials including a ratio of materials selected from the group comprising a salt and an oxide of metal; applying a blocking layer over the covert material, the blocking layer obscuring the covert material on the base document layer and preventing access to the covert material without damaging the blocking layer; and applying a machine readable data carrier to the document, the machine readable carrier storing data indicating at least one forensic metric of the covert material.

2. The method of claim 1 wherein the blocking layer prevents access to the mixture of forensic materials such that at least partial destruction of the blocking layer by tearing or combustion is required to measure the ratio.

3. The method of claim 1 further comprising computing a metric related to the ratio and embedding the metric in a layer in the document.

4. The method of claim 3 further comprising embedding the metric in a layer that includes the covert material.

5. The method of claim 3 further comprising steganographically embedding the metric in the document.

6. The method of claim 3 further comprising embedding a digital watermark carrying the metric in an image on the document.

7. The method of claim 1 wherein the covert material is printed on the base layer.

8. An identification document comprising: a first document layer; a covert material applied to a portion of the first document layer, the covert material including a carrier and a mixture of forensic materials within the carrier, the mixture of forensic materials including a ratio of materials selected from the group comprising a salt and an oxide of metal; a blocking layer applied over the covert material, the blocking layer obscuring the covert material and preventing access to the covert material without damaging the blocking layer; and a machine readable data carrier applied to the identification document, the machine readable carrier storing data indicating at least one forensic metric of the covert material.

9. The identification document of claim 8 wherein the machine readable data carrier is steganographically embedded in the document.

10. The identification document of claim 9 wherein the machine readable data carrier is a digital watermark embedded in information printed on the document.

11. The identification document of claim 8 wherein the data indicating at least one forensic metric of the covert material includes data indicating a forensic metric mathematically related to the ratio.

12. The identification document of claim 8 wherein the data indicating at least one forensic metric of the covert material includes data identifying a location of the covert materials on the first document layer.

13. The identification document of claim 8 wherein the covert material is the same color as the first document layer such that the covert material is not visible.

14. The identification document of claim 8 wherein the mixture of forensic materials including the salt and the oxide of metal is white in color such that it can be mixed with a colored ink without affecting the color of the ink.

15. The identification document of claim 8 wherein the data indicating at least one forensic metric of the covert material includes a key for decrypting the forensic metric of the covert material.

16. The identification document of claim 8 wherein the covert material comprises a coating.

17. The identification document of claim 8 wherein the covert material is printed on the first document layer.

18. The identification document of claim 8 wherein the ratio is measurable from metal ions of the mixture of forensic materials.

19. The identification document of claim 8 wherein the blocking layer prevents access to the mixture of forensic materials such that at least partial destruction of the blocking layer by combustion is required to measure the ratio.

20. An identification document comprising: a first document layer; a covert material applied at a location on the first document layer, the covert material including a carrier and a mixture of forensic materials within the carrier, the mixture of forensic materials including a ratio of materials; a blocking layer applied over the covert material, the blocking layer obscuring the covert material; and a machine readable data carrier, different from the covert material, applied to the identification document, the machine readable carrier storing data indicating the location of the covert material on the first document layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The advantages, features, and aspects of embodiments of the invention will be more fully understood in conjunction with the following detailed description and accompanying drawings, wherein:

(2) FIG. 1 is an illustrative example of an identification document;

(3) FIG. 2 is an illustrative cross section of the identification document of FIG. 1, taken along 10 the A-A line;

(4) FIG. 3 is a diagram illustrating a cross section of a document structure including one example of a forensic feature;

(5) FIG. 4 is a diagram illustrating a cross section of a document structure with an alternative example of a forensic feature;

(6) FIG. 5 is a diagram illustrating an example of identification document with forensic features embedded at one or more locations on the document, including areas with fixed and variable information.

(7) FIG. 6 is a flow diagram illustrating a method for making a document structure including a forensic feature.

(8) FIG. 7 is a flow diagram illustrating a method of making a document structure having forensic feature comprised of a ratio of salts or oxides.

(9) FIG. 8 is a flow diagram illustrating a method of making a document structure having a forensic layer and a blocking layer, where the blocking layer prevents access to the forensic layer.

(10) FIG. 9 is a flow diagram illustrating a method for evaluating a forensic feature for document authentication and forensic tracking.

(11) Of course, the drawings are not necessarily drawn to scale, with emphasis rather being placed upon illustrating the principles of the invention. In the drawings, like reference numbers indicate like elements or steps. Further, throughout this application, certain indicia, information, identification documents, data, etc., may be shown as having a particular cross sectional shape (e.g., rectangular) but that is provided by way of example and illustration only and is not limiting, nor is the shape intended to represent the actual resultant cross sectional shape that occurs during manufacturing of identification documents.

DETAILED DESCRIPTION

(12) FIG. 3 is a diagram illustrating a cross section of an identification document including a covert material (e.g., 104a-c) between document layers 100 and 102. The covert material comprises a forensic material, such as a predetermined ratio of salts or oxides of metals (preferably rare earth metals). Document layers can be made of a variety of materials used in secure documents. In our implementations, the covert material is applied to a base layer 102 and one or more additional layers 100 are then applied over the covert material. For identification documents, the base layer is typically a core or substrate of the document, and the additional layers typically comprise laminates or coatings. Our implementations are particularly suited for multi-layer ID document architectures (e.g., TESLIN-core, PVC-core or Polycarbonate-core, multi-layered ID documents), but a forensic material comprising a unique ratio of salts or oxides could be used in other secure document structures.

(13) We use salts or oxides of unique (e.g., rare earth metals) to provide a unique forensic feature in both CI and OTC ID cards. The feature is such that destruction of the card or, at least, a portion of the card is necessary to authenticate and validate the card as genuine. In other words, the presence of the feature cannot be detected by even knowledgeable professionals without tearing the card open in the correct location or by destroying the card (or portions of the card) by combustion.

(14) Additionally, more than one salt or oxide can be used so that the ratio of the individual metal ion signals can be used to verify authenticity. Analytical testing such as AE (atomic emission) or X-Ray fluorescence (ESCA) or other suitable techniques for which these metal ion compounds have distinctive signals are used to measure a forensic metric corresponding to the ratio. The use of combinations of salts or oxides offers up several advantages: 1) One does not have to be concerned with the amount of material laid down opening up the manufacturing/operational window considerably; 2) Matching the color or the base stock (TESLIN for example in our CI or OTC cards) becomes a much easier task allowing for the printing via offset or screen on any location (front or back) of the card; 3) Ratios can be chosen such that they are specific to a given issuer (e.g., a State or country) or device; and finally, 4) Multiple salts or oxides can be used to generate a forensic tracking scheme using specific ratios of compounds to define a given lot of material or day of manufacture. For example, a 4/2/1 ratio of Erbium oxide to Lanthanum oxide to Yttrium oxide could be used to indicate lot #23 for the State of Wisconsin and then a 4/1/1 ratio could be used to indicate lot #24 for the State of Illinois and so on. More specific identification of particular documents can be achieved using unique patterns and/or locations of covert material including the forensic material.

(15) In our card implementations, the requirements of the salts or oxides chosen for government issued ID cards are: 1) They are stable over time and in a wide range of temperature and humidity conditions; 2) They can be milled or dissolved into a carrier such as offset, litho, gravure, or flexo inks and that they then present viable printing ink materials; 3) They have essentially the same color (white) if they are to be applied to the base stock in an invisible fashion; and 4) If not white, then they allow formulation into a known colored ink with standard vehicles and that the resultant ink is a commercially viable one.

(16) Though not necessary, these materials can be printed in a known pattern. Preferably, the covert material comprising the salts or oxides is applied at a particular, predetermined location on the cardfront or back. The back is preferred since there is less chance for either contamination of other printing mechanisms or interference with other printing processes or card function.

(17) FIG. 4 is a diagram illustrating a cross section of a document structure with an alternative example of a forensic feature. In this example, a covert material 110 is applied to a base document layer 112. The covert material provides a forensic metric, which is measurable from the covert material for authentication and forensic tracking of the document to a source (e.g., issuer, time of manufacture and lot). A blocking layer 114, which partially or fully covers the covert material 110, is applied over the covert material. The blocking layer prevents access to the covert material such that at least partial destruction of the document is required to measure the forensic metric.

(18) Another protective layer 116 is applied over the blocking layer in this example. In ID document applications, this protective layer 116 may comprise a laminate and the base document layer 112 may comprise a core of the ID document, with the blocking and covert materials comprising layers of printed material.

(19) In one implementation, the covert material is activated by electromagnetic waves in a first band, and responds with electromagnetic waves in a second band. For example, the covert material becomes activated when exposed to electromagnetic radiation in the first band. It then responds by transmitting, emitting, reflecting or fluorescing electromagnetic waves in a second band, which may or may not differ from the first band. The blocking layer comprises a blocking property that blocks the first band, the second band, or both the first and second bands.

(20) In one particular embodiment, the blocking layer allows the waves of the activating band to substantially pass through to the covert material, yet it blocks the response from the covert material. In another embodiment, the block layer substantially blocks the waves of the activating band such that the covert material is not activated so long as the blocking layer remains in tact on the document. In both cases, the blocking layer makes the covert material undetectable without destruction of the document.

(21) In one specific embodiment, the covert material comprises a covert ink such as an IR ink. For example, an IR ink pattern is printed on the core of an ID document via offset printing. The blocking layer either blocks the waves needed to activate the IR material (e.g., cause it to fluoresce) or it allows these waves, yet blocks the response from the IR material, such as blocking the waves from the fluorescing of the IR material (which may be in a different band from the activating band). The blocking of waves in or out of the blocking layer may be achieved by putting a material in the blocking layer that absorbs light in a particular band. For example, a carbon pigment may be used to block both the activating band and the response that would otherwise result from the covert material in the absence of the blocking layer. This carbon pigment may be printed over the covert material, or contained in a coating, laminate, film or other layer applied over the covert material.

(22) Referring again to FIG. 4, the covert material 11Oa-c may be intermingled and interlocked with other material 118a-c printed on the document. Both the covert material 110 and other material 118 may be variable or fixed information. Variable information includes personal information unique to the bearer, such as photo, biometric, name, birth date, address, document number. Fixed information includes information that is common to at least a batch or lot of documents, such as issuer seal or graphic, issuer name, etc. The interlocking may be a physical interlocking: physical connection between items 110 and 118. The interlocking may also be a logical interlocking of data: the information conveyed in items 110 and 118 is the same or related through a predetermined relationship. This relationship may be a mathematical relationship, such as a hash, or a spatial relationship, such as a unique pattern comprised of the location of both items 110 and 118. Finally, the interlocking may be both physical and logical.

(23) The interlocking relationship may be conveyed through the use of machine readable data carriers (chip, RFID, magnetic strip, bar code, optical readable media, digital watermark, etc.). Items 110 and 118 themselves may be conveyed in carriers, such as inks or other media, which constitute machine readable data carriers. The machine readable data carriers may be used to: 1. store data used to logically interlock security elements on the document; 2. store the forensic metric of the covert material, such as a pattern, hash, ratio of materials, location, or other measurable attribute of the covert material; 3. store a key or other information necessary to locate, decrypt or decode the forensic metric of the covert material. In one implementation, inks used to print visible or covert inks, including the inks used to convey the covert forensic material are used to print images that include steganographically embedded information, such as digital watermarks. These digital watermarks, in turn, are used to store the information to identify, locate and verify other security features, including the forensic feature embedded in the document.

(24) FIG. 5 is a diagram illustrating an example of identification document with forensic features embedded at one or more locations on the document, including areas with fixed and variable information. The document includes a variety of features such as a photo of the bearer 118, security feature 120 physically interlocked in the photo 118, image of signature 122, bar code 124, printed issuer and bearer information 126, security feature 128 (ghost image of bearer), and other information 130, such as a biometric image, chip, optical media, etc. These various features may reside at one or more of the document layers 132, 134. The covert material may be printed in one or more of these areas so as to be interlocked with these features. The covert material may also be embedded in different document layers 132, 134. Finally, the covert material may have attributes, such as a pattern, forensic metric, etc. that are stored on the machine readable data carriers on the document. The machine readable information may then be read and used to locate, decode, decrypt and/or verify the validity of the forensic feature in the covert material.

(25) FIG. 6 is a flow diagram illustrating a method for making a document structure including a forensic feature. The covert material formulation is prepared, such as by mixing a carrier with forensic material, such as mixing an ink with particular ratio of compounds or covert pigments (200). This covert material is then applied to the base document layer, which can vary depending on the document architecture at issue (e.g., a core, laminate, film, etc.) (202). Next, one or more layers are applied over the covert material (204). Finally, forensic data in the document is captured and stored in a database to maintain the association between the document and forensic data that it includes.

(26) The left hand side of FIG. 6 shows that the document layers including a link to the forensic feature may be applied to the document at various stages in document production, including before, during or after application of the covert material (208-212). For example, each of these layers, including the layer that includes the covert material itself, may include a machine readable data carrier that stores attributes of the forensic feature, such as the forensic metric (ratio of materials, pattern of covert material, etc.). The link need not be implemented with a machine readable data carrier; it may be a human verifiable relationship as well. However, machine readable data carriers facilitate machine verification, as well as the use of machine computing to implement encryption of the forensic metric and forensic data, secure hashing to create unique relationships between the forensic feature and its hash stored elsewhere on the document or database, and steganographic techniques for hiding forensic metrics and data within other data on the document. These techniques enable complex relationships among the data carriers and data stored in the database that are used to verify authenticity with high degree of certainty and detect document tampering by identifying where these relationships have been broken (e.g., hashes do not match, data cannot be decrypted into usable form because key decoded form document is invalid, forensic feature has invalid pattern in invalid location, forensic feature absent in location specified within encrypted data carrier, etc.). One example is to derive data from the forensic feature, such as the forensic metric (including a hash of the metric), scramble this data (encrypting with one or more private or public keys), encode it in a data message (using error correction coding), and steganographically embed this data message on the document. This steganographic embedding may take the form of a digital watermark embedded in an image printed on the document by subtly altering that image as well as embedded in data stored on a machine readable data carrier on the document (e.g., embedded in image or other biometric data in chip, bar code, or optical memory element). Methods for embedding digital watermarks are described in U.S. Pat. Nos. 6,122,403 and 6,614,914, which are hereby incorporated by reference.

(27) FIG. 7 is a flow diagram illustrating a method of making a document structure having forensic feature comprised of a ratio of salts or oxides. The method includes mixing the salt or oxide of rare earth metal into a carrier, such as an ink or coating (300). The carrier is then applied to the document by printing or coating (302). This printing operation may be adapted for printing and coating machines used in either CI or OTC ID document production. For example, it may include printing with offset, litho, or gravure equipment. Alternatively, the carrier may comprise a thermal transfer printer panel (such as a panel used in D2T2 printer ribbons). Alternatively, the carrier may comprise an ink used in ink jet printing or a toner for use in Xerographic printing. One or more layers may then be applied over the carrier of the forensic material (304). Finally, the forensic data conveyed in the forensic material, such as the ratio of salts/oxides, is added to the database, which stores data about the document (306). This data may also include information about the equipment used to print the equipment, the issuer or operator, the issuer location, the time and date of manufacture or issue, etc. Preferably, data referring back to this database entry, such as a document identification number, is embedded, printed and/or otherwise stored on the document.

(28) Block 308 illustrates that the process includes computing a relationship between the forensic metric and information to be embedded on the document. In one implementation, this relationship means that the metric is embedded elsewhere or some mathematical derivative of it is embedded elsewhere on the document. This relationship may be encoded in a pattern and embedded on the document. In some cases, it is preferable to apply the forensic material, measure the metric, and then encode this metric in the database and/or document. This enables any changes to the metric due to application of the metric to the document to be taken into account before recording it. Alternatively, if the forensic metric is expected not to change, it may be embedded on the document before the forensic material is applied to the document.

(29) FIG. 8 is a flow diagram illustrating a method of making a document structure having a forensic layer and a blocking layer, where the blocking layer prevents access to the forensic layer. The forensic layer comprises a layer with forensic material, such as a ratio of rare compounds or covert material. The blocking layer comprise a material used to prevent access to the forensic material, such that deconstruction of the document is required to access the forensic material. The method creates the forensic and blocking layers (400), applies the forensic layer (402) and applies the blocking layer (404). In particular implementations, the blocking and forensic layers may be created and applied at different times, such as at the time of creating ID card stock and at the time of personalizing the ID card stock with information of an applicant. An additional layer may also be added (406) to cover the blocking layer, such as a protective overlaminate or hard coat (e.g., a UV or EB curable hard coat). As discussed in connection with FIG. 7, the relationship between a forensic metric and the information embedded within one or more layers of the document may be created and used at various stages in the process.

(30) FIG. 9 is a flow diagram illustrating a method for evaluating a forensic feature for document authentication and forensic tracking. The method begins by reading information embedded in the document (500). For example, the document is scanned and information is extracted from machine readable data carriers. Preferably, information related to the forensic feature is steganographically embedded in the document through the use of a digital watermark as described previously. In this case, the reading may include scanning an image, detecting the digital watermark in the image, decoding the message payload of the watermark (e.g., using one or more public or private watermark decoding keys), and decrypting the message (e.g., using one or more private or public encryption keys). The watermark message may include information identifying the location of the forensic feature, or may provide an index to a database that provides information about the document, including the expected forensic information. This or other predetermined information is used to determine the location of the forensic feature (502). The document is then deconstructed, and preferably, it is deconstructed at the forensic feature location (504). At this stage, an additional reading of embedded information may be performed after one or more layers (e.g., layers blocked by the blocking layer) have been exposed through the deconstruction process (506). This information may include information used to verify the forensic feature as described previously.

(31) Next the forensic feature is analyzed to measure the forensic feature (508). This may include an analysis of metal ion signals to measure the ratio of compounds. It may also include analyzing covert pigments revealed after deconstruction of a blocking layer. The covert pigment may be designed to have a unique signature, or convey a unique pattern as a forensic metric. The validity of the document is checked by evaluating the relationship between this measured metric and the metric stored in the embedded information on the document and/or information in a database. Further, the forensic metric itself conveys data as to the source of the document in cases where the metric is specifically chosen to correspond to the source (lot, time of manufacture, issuer, issuer location, device of manufacture, etc.). To check the source, the metric may be looked up in a database to find the source information corresponding the metric measured in the document.

(32) Concluding Remarks

(33) Having described and illustrated the principles of the technology with reference to specific implementations, it will be recognized that the technology can be implemented in many other, different, forms, and in many different environments.

(34) The technology disclosed herein can be used in combination with other technologies. Also, instead of ID documents, the inventive techniques can be employed with product tags, product packaging, labels, business cards, bags, charts, smart cards, maps, labels, etc. The term ID document is broadly defined herein to include these tags, maps, labels, packaging, cards, etc.

(35) It should be understood that, in the Figures of this application, in some instances, a plurality of method steps may be shown as illustrative of a particular method, and a single method step may be shown as illustrative of a plurality of a particular method steps. It should be understood that showing a plurality of a particular element or step is not intended to imply that a system or method implemented in accordance with the invention must comprise more than one of that element or step, nor is it intended by illustrating a single element or step that the invention is limited to embodiments having only a single one of that respective elements or steps. In addition, the total number of elements or steps shown for a particular system element or method is not intended to be limiting; those skilled in the art will recognize that the number of a particular system element or method steps can, in some instances, be selected to accommodate the particular user needs.

(36) To provide a comprehensive disclosure without unduly lengthening the specification, applicants hereby incorporate by reference each of the U.S. patent documents referenced above.

(37) The technology and solutions disclosed herein have made use of elements and techniques known from the cited documents. Other elements and techniques from the cited documents can similarly be combined to yield further implementations within the scope of the present invention.

(38) Thus, the exemplary embodiments are only selected samples of the solutions available by combining the teachings referenced above. The other solutions necessarily are not exhaustively described herein, but are fairly within the understanding of an artisan given the foregoing disclosure and familiarity with the cited art. The particular combinations of elements and features in the above-detailed embodiments are exemplary only; the interchanging and substitution of these teachings with other teachings in this and the incorporated-by-reference patent documents are also expressly contemplated.

(39) In describing the embodiments of the invention illustrated in the figures, specific terminology is used for the sake of clarity. However, the invention is not limited to the specific terms so selected, and each specific term at least includes all technical and functional equivalents that operate in a similar manner to accomplish a similar purpose.