U.S. patent application number 15/387145 was filed with the patent office on 2017-04-13 for authenticating printed objects.
The applicant listed for this patent is Tony F. Rodriguez, Ravi K. Sharma. Invention is credited to Tony F. Rodriguez, Ravi K. Sharma.
Application Number | 20170103493 15/387145 |
Document ID | / |
Family ID | 36337170 |
Filed Date | 2017-04-13 |
United States Patent
Application |
20170103493 |
Kind Code |
A1 |
Rodriguez; Tony F. ; et
al. |
April 13, 2017 |
AUTHENTICATING PRINTED OBJECTS
Abstract
The application discloses printed objects including encoded
information, and methods, apparatus and systems for authenticating
such printed objects. Some such objects, methods and apparatus
involve data hiding and/or encoded signals.
Inventors: |
Rodriguez; Tony F.;
(Portland, OR) ; Sharma; Ravi K.; (Portland,
OR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Rodriguez; Tony F.
Sharma; Ravi K. |
Portland
Portland |
OR
OR |
US
US |
|
|
Family ID: |
36337170 |
Appl. No.: |
15/387145 |
Filed: |
December 21, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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14805233 |
Jul 21, 2015 |
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15387145 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G07D 7/12 20130101; G07D
7/20 20130101; G06T 1/0021 20130101; B42D 25/23 20141001; B42D
25/333 20141001; B42D 25/00 20141001; G07D 7/0051 20170501; B41M
3/10 20130101; G07D 7/0057 20170501; G06K 9/46 20130101; G06T
1/0028 20130101; G06T 2201/0051 20130101; G06K 9/22 20130101; G07D
7/0055 20170501; B42D 25/328 20141001; G07D 7/0053 20130101; B42D
2033/20 20130101; B42D 2035/24 20130101 |
International
Class: |
G06T 1/00 20060101
G06T001/00 |
Claims
1. An image processing method for encoding auxiliary data within a
digital image, in which the digital image includes a plurality of
line elements, said method comprising: determining a dominate angle
associated with the plurality of line elements; and in a digital
space, and using an electronic processor, varying line angles of at
least a set of the plurality of line elements relative to the
dominate angle, in which the varying line angles conveys the
auxiliary data.
2. The image processing method of claim 1 in which the encoding
comprises steganographic encoding.
3. The image processing method of claim 1 in which the encoding
comprises digital watermarking.
4. The image processing method of claim 1 in which the auxiliary
data comprises plural-bit information.
5. The image processing method of claim 1 in which the set
comprises at least two (2) line elements.
6. The image processing method of claim 1 in which the plurality of
line elements comprise vertical and horizontal lines.
7. An image processing method for encoding information within an
image, in which the image includes a plurality of line structures,
said method comprising: identifying a dominate orientation
associated with the plurality of line structures; and, using an
electronic processor, varying line orientation of at least a set of
the plurality of line structures relative to the dominate angle, in
which the varying line orientation conveys the information.
8. The image processing method of claim 7 in which the encoding
comprises steganographic encoding.
9. The image processing method of claim 7 in which the encoding
comprises digital watermarking.
10. The image processing method of claim 7 in which the information
comprises plural-bit information.
11. The image processing method of claim 7 in which the set
comprises at least two (2) line structures.
12. The image processing method of claim 7 in which the plurality
of line structures comprise vertical and horizontal lines.
13. The image processing method of claim 7 in which the dominate
orientation comprises a base orientation.
14. A physical object comprising: a first surface; and an image
printed on the first surface, the image comprising a plurality of
line elements encoding auxiliary data, the plurality of line
elements comprising a dominate angle associated therewith, in which
a set of the plurality of line elements comprise varied line angles
relative to the dominate angle, and in which the varied line angles
convey the auxiliary data.
15. The physical object of claim 14 in which the encoding comprises
steganographic encoding.
16. The physical object of claim 14 in which the encoding comprises
digital watermarking.
17. The physical object of claim 14 in which the auxiliary data
comprises plural-bit information.
18. The physical object of claim 14 in which the set comprises at
least two (2) line elements.
19. The physical object of claim 14 in which the plurality of line
elements comprise vertical and horizontal lines.
20. The physical object of claim 14 in which the auxiliary data
comprises a machine recognizable pattern.
21. A document comprising the physical object of claim 14.
22. A physical object comprising: a first surface; and an image
printed on the first surface, the image comprising a plurality of
line structures, the plurality of line structures comprising a
dominate orientation associated therewith, in which a set of the
plurality of line structures comprise varied orientation relative
to the dominate orientation, and in which the varied line
orientation conveys information.
23. The physical object of claim 22 in which the information
comprises steganographic encoding.
24. The physical object of claim 22 in which the information
comprises digital watermarking.
25. The physical object of claim 22 in which the information
comprises plural-bit information.
26. The physical object of claim 22 in which the set comprises at
least two (2) line structures.
27. The physical object of claim 22 in which the plurality of line
structures comprise vertical and horizontal lines.
28. The physical object of claim 22 in which the dominate
orientation comprises a base orientation.
29. The physical object of claim 22 in which the information
comprises a machine recognizable pattern.
30. The physical object of claim 22 in which the varied orientation
comprises a plurality of varied orientations.
31. A document comprising the physical object of claim 22.
Description
RELATED APPLICATION DATA
[0001] This application is a division of U.S. patent application
Ser. No. 14/805,122, filed Jul. 21, 2015 (published as US
2016-0189326 A1), which is a continuation of U.S. patent
application Ser. No. 13/488,942, filed Jun. 5, 2012 (now U.S. Pat.
No. 9,087,376) which is a continuation of U.S. patent application
Ser. No. 12/970,629, filed Dec. 16, 2010 (now U.S. Pat. No.
8,194,919), which is a continuation of U.S. application Ser. No.
11/270,802, filed Nov. 8, 2005 (now U.S. Pat. No. 7,856,116) which
claims the benefit of U.S. Provisional Patent Application Nos.:
60/626,529, filed Nov. 9, 2004; 60/670,773, filed Apr. 11, 2005;
and 60/674,793, filed Apr. 25, 2005. This application is related to
assignee's U.S. Pat. Nos. 6,754,377 (including Appendix A);
5,850,481; 5,636,292; 5,710,834; 5,748,763; 5,748,783; 5,841,978;
5,832,119; 5,822,436 (including the entire certificate of
correction); 5,862,260; 6,122,403; 6,026,193; 5,809,160; and
publication Nos. US 2004-0250080 A1 and US 2005-0041835 A1, and US
Provisional Application No. 60/651,814, filed Feb. 10, 2005. Each
of the above patent documents is hereby incorporated by reference
in its entirety.
BACKGROUND AND SUMMARY
[0002] The present disclosure relates to steganography, digital
watermarking and security enhancements.
[0003] Digital watermarking is a form of steganography that
encompasses a great variety of techniques by which plural bits of
digital data are hidden in some other object without leaving
human-apparent evidence of alteration.
[0004] Digital watermarking may be used to modify media content to
embed a message or machine-readable code into the content. The
content may be modified such that the embedded code is
imperceptible or nearly imperceptible to the user, yet may be
detected through an automated detection process.
[0005] Most commonly, digital watermarking is applied to media such
as images, audio signals, and video signals. However, it may also
be applied to other types of data, including documents (e.g.,
through line, word or character shifting, through texturing,
graphics, or backgrounds, etc.), software, multi-dimensional
graphics models, and surface textures of objects.
[0006] Digital watermarking systems typically have two primary
components: an embedding component that embeds the watermark in the
media content, and a reading component that detects and reads the
embedded watermark. The embedding component embeds a watermark by
altering data samples of the media content (e.g., pixel values, DCT
coefficients, wavelet coefficients, etc). The reading component
analyzes content to detect whether a watermark is present. In
applications where the watermark encodes information, the reading
component extracts this information from the detected watermark.
Commonly assigned U.S. Pat. No. 6,614,914 and 5,862,260 discloses
various encoding and decoding techniques.
[0007] Some aspects of the disclosure relate to inconspicuously
embedding binary data in line art images (such as are used in
currency, graphics, identification documents and the like), and
associated methods/systems for decoding such data from such images
Other aspects of the disclosure relate to security features and
confidence clues for identification documents, currency, graphics
and the like. Still other aspects of the disclosure provide related
systems and methods.
[0008] In the following disclosure it should be understood that
references to watermarking encompass not only the assignee's
watermarking technology, but can likewise be practiced with any
other watermarking technology.
[0009] Some of the prior art in image watermarking has focused on
pixelated imagery (e.g. bit-mapped images, JPEG/MPEG imagery,
VGA/SVGA display devices, etc.). In some watermarking techniques,
the luminance or color values of component pixels are slightly
changed to effect subliminal encoding of binary data through the
image (This encoding can be done directly in the pixel domain, or
in another domain, such as the DCT domain.) In some systems,
isolated pixels are changed in accordance with one or more bits of
the binary data; in others, plural domain-related groupings of
pixels (e.g. locally adjoining, or corresponding to a given DCT
component) are so changed. In all cases, however, pixels have
served as the ultimate carriers of the embedded data.
[0010] One inventive technique for authentication and copy
detection employs ink pairs to provide authentication clues for
security documents (e.g., banknotes, currency, checks, financial
instruments, etc.) and identification documents (e.g., driver's
license, passport, visa, ID card, bank cards, etc.). An ink pair
cooperates to provide a diffraction grating (or other reflective
pattern) while obscuring the location of a metallic ink--one of two
inks in an ink pair.
[0011] According to one aspect, a document includes a first surface
and a second surface. The first surface comprises a first set of
print structures and a second set of print structures. The first
set of print structures and the second set of print structures
cooperate to obscure the location on the first surface of the
second set of print structures. The second set of print structures
is arranged on the first surface so as to provide a reflective
pattern.
[0012] In a related example, the reflective pattern forms a
diffraction grating.
[0013] In another related example, the first set of print
structures is provided on the first surface with a first ink and
the second set of print structures is provided on the first surface
with a second different ink. The second different ink is a metallic
ink.
[0014] In still another related example, the first set of print
structures and the second set of print structures collective convey
a steganographic signal (e.g., a digital watermark) that is
discernable from optical scan data representing at least a first
portion of the first surface.
[0015] According to another aspect of the disclosure, a photo
identification document includes a first surface and a second
surface. The second surface includes a photographic representation
(e.g., a picture or photo) of an authorized bearer of the photo
identification document. The first surface comprises a first set of
print structures provided thereon with a first ink having a first
color and a second set of print structures provided thereon with a
second ink having a second color. The first color and the second
color are visually similar colors. The first set of print
structures and the second set of print structures cooperate to
obscure the location on the first surface of the second set of
print structures. The second ink comprises metallic characteristics
so when arranged on the first surface, the second set of print
structures provide a diffraction grating.
[0016] According to still another aspect of the disclosure, a
security document (e.g., a banknote, check, note, draft, etc.)
includes a first surface; a first set of print structures provided
on the first surface with a first ink having a first color; and a
second set of print structures provided on the first surface with a
second ink having a second color. The first color and the second
color are visually similar colors. The first set of print
structures and the second set of print structures cooperate to
obscure the location on the first surface of the second set of
print structures. The second ink comprises metallic characteristics
so when arranged on the first surface, the second set of print
structures provide a pattern that, in response to a signal or
radiation, reflects a predetermined signal or pattern.
[0017] The foregoing features and advantages of the disclosure will
be more readily apparent from the following detailed description,
which proceeds with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIGS. 1A and 1B show prior art techniques for achieving
grayscale effects using line art.
[0019] FIG. 2 shows a virtual array of grid points that can be
imposed on an image according to one embodiment of the present
disclosure.
[0020] FIG. 3 shows a virtual array of regions that can be imposed
on an image according to the FIG. 2 embodiment. FIG. 4 shows an
excerpt of FIG. 3 with a line from a line art image passing
therethrough.
[0021] FIG. 5 shows changes to the width of the line of FIG. 3 to
effect watermark encoding according to one embodiment of the
present disclosure.
[0022] FIG. 6 shows changes to the position of the line of FIG. 3
to effect watermark encoding according to another embodiment of the
present disclosure.
[0023] FIG. 7 is a block diagram of a photocopier according to
another embodiment of the disclosure.
[0024] FIG. 8 shows a line angle modulation watermark signal.
[0025] FIG. 9a shows a first surface of a document including a
transparent or semi-transparent window; and FIG. 9b shows of a
second surface of the document including the transparent or
semi-transparent window.
[0026] FIG. 10 shows a relationship between cash and
confidence.
[0027] FIG. 11 illustrates a document including a first
surface.
[0028] FIG. 11A illustrates an ink pair arranged in a pattern on
the first surface of FIG. 11. This area is enlarged for the
reader's convenience.
[0029] FIGS. 11B and 11C illustrate ink pairs arranged in
alternative patterns.
[0030] FIG. 11D illustrates ink dots or blobs arranged to provide a
reflective pattern. The dots or blobs are enlarged for the reader's
convenience.
[0031] FIG. 12 illustrates the appearance of the FIG. 11A pattern
to a casual human observer.
[0032] FIG. 13 highlights a portion of a diffraction grating for
the FIG. 11A pattern.
[0033] FIG. 14 illustrates pattern detection for a
transceiver/authenticator.
[0034] FIG. 15 illustrates an exaggerated view of a security
document including security fibers.
[0035] FIG. 16 illustrates a spatial mapping of the fibers shown in
FIG. 15.
[0036] FIG. 17 illustrates a portable consumer device displaying
the spatial mapping of FIG. 16.
[0037] FIG. 18 is a diagram illustrating observation of a
watermarked image at an off-normal viewing angle.
DETAILED DESCRIPTION
Line Art
[0038] While pixelated imagery is a relatively recent development,
line art goes back centuries. One familiar example is U.S. paper
currency. On the one dollar banknote, for example, line art is used
in several different ways. One is to form intricate webbing
patterns around the margin of the note (generally comprised of
light lines on dark background). Another is so form grayscale
imagery, such as the portrait of George Washington (generally
comprised of dark lines on a light background).
[0039] There are two basic ways to simulate grayscales in line art.
One is to change the relative spacings of the lines to effect a
lightening or darkening of an image region. FIG. 1A shows such an
arrangement; area B looks darker than area A due to the closer
spacings of the component lines. The other technique is to change
the widths of the component lines--wider lines resulting in darker
areas and narrower lines resulting in lighter areas. FIG. 1B shows
such an arrangement. Again, area B looks darker than area A, this
time due to the greater widths of the component lines. These
techniques are often used together.
[0040] Some specific embodiments of steganographic encoding using
line art techniques are provided below.
[0041] One embodiment posits a virtual grid of points imposed on a
line art image (e.g. a U.S. one dollar banknote), with the points
spaced at regular intervals in vertical and horizontal directions.
(The horizontal and vertical intervals need not be equal.) The
virtual points may be imposed over some or all of the bill at equal
vertical and horizontal spacings of 250 pm. In regions of the
banknote having line art, the component lines of the art snake in
and amongst these virtual grid points.
[0042] Each grid point is considered to be the center of a
rounded-square region. The luminance of the region is a function of
the proximity of any line(s) within the boundary of the region to
the region's centerpoint, and the thickness of the line(s).
[0043] To change the luminance of the region, the contour of the
line(s) is changed slightly within the region. In particular, the
line is made slightly thicker to decrease luminance; or thinner to
increase luminance (Unless otherwise noted, dark lines on light
backgrounds are presumed.) The ability to effect these slight
changes is then employed, in accordance with known pixelation-based
watermarking techniques, to encode binary data in the line art. If
such a banknote is thereafter scanned by a scanner, the values of
the pixel data produced by the scanner will reflect the foregoing
alterations in luminance values, permitting embedded watermark data
to be decoded. In an alternative embodiment, the line widths are
not changed. Instead, the positions of the lines are shifted
slightly towards or away from certain virtual grid points to effect
an increase or decrease in the corresponding area's luminosity,
with the same effect. Other embodiments are also detailed.
[0044] By the techniques disclosed herein, line art images can be
encoded to subliminally convey binary data. This capability permits
various hardware systems to recognize banknotes, and to change or
limit their actions in a predetermined manner (e.g. a photocopier
equipped with this capability can refuse to reproduce banknotes, or
can insert forensic tracer data in the copy).
[0045] Advances in digital imaging and printing technologies have
vastly improved desktop publishing, yet have provided
counterfeiters with low cost technologies for illegally
counterfeiting security documents (e.g., banknotes, checks, notes,
drafts, and other financial instruments) and identification
documents (e.g., driver's licenses, passports, ID documents, visa,
etc.). While there are many technologies that make counterfeiting
more difficult, there is a need for technologies that can quickly
and accurately detect originals and distinguish copies. Preferably,
these technologies integrate with existing processes for handling
such documents.
[0046] Referring to FIG. 2, an illustrative form of the disclosure
employs a grid 10 of imaginary reference points arrayed over a line
art image. The spacing between points is 250 .mu.m in the
illustrated arrangement, but greater or lesser spacings can of
course be used.
[0047] Associated with each grid point is a surrounding region 12,
shown in FIG. 3. As described below, the luminosity (or
reflectance) of each of these regions 12 is slightly changed to
effect the subliminal encoding of binary data.
[0048] Region 12 can take various shapes; the illustrated
rounded-rectangular shape is representative only. (The illustrated
shape has the advantage of encompassing a fairly large area while
introducing fewer visual artifacts than, e.g., square regions.) In
other embodiments, squares, rectangles, circles, ellipses, etc.,
can alternatively be employed.
[0049] FIG. 4 is a magnified view of an excerpt of FIG. 3, showing
a line 14 passing through the grid of points. The width of the
line, of course, depends on the particular image of which it is a
part. The illustrated line is about 25 pm in width; greater or
lesser widths can naturally be used.
[0050] In a first embodiment of the disclosure, shown in FIG. 5,
the width of the line is controllably varied so as to change the
luminosity of the regions through which it passes. To increase the
luminosity (or reflectance), the line is made narrower (i.e. less
ink in the region). To decrease the luminosity, the line is made
wider (i.e. more ink).
[0051] Whether the luminance in a given region should be increased
or decreased depends on the particular watermarking algorithm used.
Any algorithm can be used, by changing the luminosity of regions 12
as the algorithm would otherwise change the luminance or colors of
pixels in a pixelated image.
[0052] In an exemplary algorithm, the binary data is represented as
a sequence of -1 s and 1 s, instead of 0 s and 1 s. (The binary
data can comprise a single datum, but more typically comprises
several. In an illustrative embodiment, the data comprises 100
bits.)
[0053] Each element of the binary data sequence is then multiplied
by a corresponding element of a pseudo-random number sequence,
comprised of -1 s and 1 s, to yield an intermediate data signal.
Each element of this intermediate data signal is mapped to a
corresponding sub-part of the image, such as a region 12. The image
in (and optionally around) this region is analyzed to determine its
relative capability to conceal embedded data, and a corresponding
scale factor is produced. Exemplary scale factors may range from 0
to 3. The scale factor for the region is then multiplied by the
element of the intermediate data signal mapped to the region in
order to yield a "tweak" value for the region. In the illustrated
case, the resulting tweaks can range from -3 to 3. The luminosity
of the region is then adjusted in accordance with the tweak value.
A tweak value of -3 may correspond to a -5% change in luminosity;
-2 may correspond to -2% change; -1 may correspond to -1% change; 0
may correspond to no change; 1 may correspond to +1% change; 2 may
correspond to +2% change, and 3 may correspond to +5% change. (This
example follows the basic techniques described in the Real Time
Encoder embodiment disclosed in patent 5,710,834.)
[0054] In FIG. 5, the watermarking algorithm determined that the
luminance of region A should be reduced by a certain percentage,
while the luminance of regions C and D should be increased by
certain percentages.
[0055] In region A, the luminance is reduced by increasing the line
width. In region D, the luminance is increased by reducing the line
width; similarly in region C (but to a lesser extent).
[0056] No line passes through region B, so there is no opportunity
to change the region's luminance This is not fatal to the method,
however, since the watermarking algorithm redundantly encodes each
bit of data in sub-parts spaced throughout the line art image.
[0057] The changes to line widths in regions A and D of FIG. 5 are
exaggerated for purposes of illustration. While the illustrated
variance is possible, most implementations will modulate the line
width 3-50% (increase or decrease).
[0058] (Many watermarking algorithms routinely operate within a
signal margin of about +/-1% changes in luminosity to effect
encoding. That is, the "noise" added by the encoding amounts to
just 1% or so of the underlying signal. Lines typically don't
occupy the full area of a region, so a 10% change to line width may
only effect a 1% change to region luminosity, etc. Banknotes are
different from photographs in that the art need not convey
photorealism. Thus, banknotes can be encoded with higher energy
than is used in watermarking photographs, provided the result is
still aesthetically satisfactory. To illustrate, localized
luminance changes on the order of 10% are possible in banknotes,
while such a level of watermark energy in photographs would
generally be considered unacceptable. In some contexts, localized
luminance changes of 20, 30, 50 or even 100% are acceptable.)
[0059] In the illustrated embodiment, the change to line width is a
function solely of the tweak to be applied to a single region.
Thus, if a line passes through any part of a region to which a
tweak of 2% is to be applied, the line width in that region is
changed to effect the 2% luminance difference. In variant
embodiments, the change in line width is a function of the line's
position in the region. In particular, the change in line width is
a function of the distance between the region's center grid point
and the line's closest approach to that point. If the line passes
through the grid point, the full 2% change is effected. At
successively greater distances, successively less change is
applied. The manner in which the magnitude of the tweak changes as
a function of line position within the region can be determined by
applying one of various interpolation algorithms, such as the
bi-linear, bi-cubic, cubic splines, custom curve, etc.
[0060] In other variant embodiments, the change in line width in a
given region is a weighted function of the tweaks for adjoining or
surrounding regions. Thus, the line width in one region may be
increased or decreased in accordance with a tweak value
corresponding to one or more adjoining regions.
[0061] Combinations of the foregoing embodiments can also be
employed.
[0062] In the foregoing embodiments, it is sometimes necessary to
trade-off the tweak values of adjoining regions. For example, a
line may pass along a border between regions, or pass through the
point equidistant from four grid points ("equidistant zones"). In
such cases, the line may be subject to conflicting tweak
values--one region may want to increase the line width, while
another may want to decrease the line width. (Or both may want to
increase the line width, but differing amounts.) Similarly in cases
where the line does not pass through an equidistant zone, but the
change in line width is a function of a neighborhood of regions
whose tweaks are of different values. Again, known interpolation
functions can be employed to determine the weight to be given the
tweak from each region in determining what change is to be made to
the line width in any given region.
[0063] In the exemplary watermarking algorithm, the average change
in luminosity across the image is zero, so no generalized
lightening or darkening of the image is apparent. The localized
changes in luminosity are so minute in magnitude, and localized in
position, that they are essentially invisible (e.g.
inconspicuous/subliminal) to human viewers.
[0064] An alternative embodiment is shown in FIG. 6, in which line
position is changed rather than line width.
[0065] In FIG. 6 the original position of the line is shown in
dashed form, and the changed position of the line is shown in solid
form. To decrease a region's luminosity, the line is moved slightly
closer to the center of the grid point; to increase a region's
luminosity, the line is moved slightly away. Thus, in region A, the
line is moved towards the center grid point, while in region D it
is moved away.
[0066] It will be noted that the line on the left edge of region A
does not return to its nominal (dashed) position as it exits the
region. This is because the region to the left of region A also is
to have decreased luminosity. Where possible, it is generally
preferable not to return a line to its nominal position, but
instead permit shifted lines to remain shifted as they enter
adjoining regions. So doing permits a greater net line movement
within a region, increasing the embedded signal level. Again, the
line shifts in FIG. 6 are somewhat exaggerated. More typical line
shifts are on the order of 3-50 .mu.m.
[0067] One way to think of the FIG. 6 embodiment is to employ a
magnetism analogy. The grid point in the center of each region can
be thought of as a magnet. It either attracts or repels lines. A
tweak value of -3, for example, may correspond to a strong-valued
attraction force; a tweak value of +2 may correspond to a
middle-valued repulsion force, etc. In FIG. 6, the grid point in
region A exhibits an attraction force (i.e. a negative tweak
value), and the grid point in region D exhibits a repulsion force
(e.g. a positive tweak value).
[0068] The magnetic analogy is useful because the magnetic effect
exerted on a line depends on the distance between the line and the
grid point. Thus, a line passing near a grid point is shifted more
in position than a line near the periphery of the region.
[0069] Each of the variants discussed above in connection with FIG.
5 is likewise applicable to FIG. 6.
[0070] Combinations of the embodiments of FIGS. 5 and 6 can of
course be used, resulting in increased watermark energy, better
signal-to-noise ratio and, in many cases, less noticeable
changes.
[0071] In still a further embodiment, the luminance in each region
is changed while leaving the line unchanged. This can be effected
by sprinkling tiny dots of ink in the otherwise-vacant parts of the
region. In high quality printing, of the type used with banknotes,
droplets on the order of 3 .mu.m in diameter can be deposited.
(Still larger droplets are still beyond the perception threshold
for most viewers.) Speckling a region with such droplets (either in
a regular array, or random, or according to a desired profile such
as Gaussian), can readily effect a 1% or so change in luminosity.
(Usually dark droplets are added to a region, effecting a decrease
in luminosity. Increases in luminosity can be effected by speckling
with a light colored ink, or by forming light voids in line art
otherwise present in a region.)
[0072] In a variant of the speckling technique, very thin mesh
lines can be inserted in the artwork--again to slightly change the
luminance of one or more regions.
[0073] Although not previously mentioned, it is contemplated that
the banknote will include some manner of calibration information to
facilitate registration of the image for decoding. This calibration
information can be steganographic or overt. Several techniques for
steganographically embedding calibration information are disclosed
in my prior patents and applications. Other techniques can be found
in others of the cited work.
[0074] To decode watermark data, the encoded line art image must be
converted into electronic form for analysis. This conversion is
typically performed by a scanner. Scanners are well known, so a
detailed description is not provided here. Suffice it to say that
scanners conventionally employ a line of closely spaced
photodetector cells that produce signals related to the amount of
the light reflected from successive swaths of the image. Most
inexpensive consumer scanners have a resolution of 300 dots per
inch (dpi), or a center to center spacing of component
photodetectors of about 84 .mu.m. Higher quality scanners of the
sort found in most professional imaging equipment and photocopiers
have resolutions of 600 dpi (42 .mu.m), 1200 dpi (21 .mu.m), or
better.
[0075] Taking the example of a 300 dpi scanner (84 .mu.m
photodetector spacing), each 250 .mu.m region 12 on the banknote
will correspond to about a 3.times.3 array of photodetector
samples. Naturally, only in rare instances will a given region be
physically registered with the scanner so that nine photodetector
samples capture the luminance in that region, and nothing else.
More commonly, the line art is skewed with respect to the scanner
photodetectors, or is longitudinally misaligned (i.e. some
photodetectors image sub-parts of two adjoining regions). However,
since the scanner oversamples the regions, the luminance of each
region can unambiguously be determined.
[0076] In one embodiment, the scanned data from the line art is
collected in a two dimensional array and processed--according to
one of the techniques disclosed in my prior patents and
applications--to detect the embedded calibration information. The
array is then processed to effect a virtual re-registration of the
image data. A software program then analyzes the statistics of the
re-registered data (using the techniques disclosed in my prior
writings) to extract the bits of the embedded data.
[0077] In a variant embodiment, the scanned data is not assembled
in a complete array prior to the processing. Instead, it is
processed in real-time, as it is generated, in order to detect
embedded watermark data without delay. (Depending on the parameters
of the scanner, it may be necessary to scan a half-inch or so of
the line art image before the statistics of the resulting data
unambiguously indicate the presence of a watermark.)
[0078] In accordance with another aspect of the disclosure, various
hardware devices are provided with the capability to recognize
embedded watermark data in any line art images they process, and to
respond accordingly.
[0079] One example is a color photocopier. Such devices employ a
color scanner to generate sampled (pixel) data corresponding to an
input media (e.g. a dollar bill). If watermark data associated with
a banknote is detected, the photocopier can take one or more steps.
One option is simply to interrupt copying, and display a message
reminding the operator that it is illegal to reproduce
currency.
[0080] Another option is to dial a remote service and report the
attempted reproduction of a banknote. Photocopiers with dial-out
capabilities are known in the art (e.g. U.S. Pat. No. 5,305,199)
and are readily adapted to this purpose. The remote service can be
an independent service, or can be a government agency.
[0081] Yet another option is to permit the copying, but to insert
forensic tracer data in the resultant copy. This tracer data can
take various forms. Steganographically encoded binary data is one
example. An example is shown in U.S. Pat. No. 5,568,268. 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. (Such an arrangement is shown in
FIG. 7.)
[0082] Desirably, the scan data is analyzed on a line-by-line basis
in order to identify illicit photocopying with a minimum of delay.
If a banknote is scanned, one or more lines of scanner output data
may be provided to the photocopier's reprographic unit before the
banknote detection decision has been made. In this case the
photocopy will have two regions: a first region that is not
tracer-marked, and a second, subsequent region in which the tracer
data has been inserted.
[0083] Photocopiers with other means to detect not-to-be-copied
documents are known in the art, and employ various response
strategies. Examples are detailed in U.S. Pat. Nos. 5,583,614,
4,723,149, 5,633,952, 5,640,467, and 5,424,807.
[0084] Another hardware device that can employ the foregoing
principles is a standalone scanner. A programmed processor (or
dedicated hardware) inside the scanner analyzes the data being
generated by the device, and responds accordingly.
[0085] Yet another hardware device that can employ the foregoing
principles is a printer. A processor inside the device analyzes
graphical image data to be printed, looking for watermarks
associated with banknotes.
[0086] For both the scanner and printer devices, response
strategies can include disabling operation, or inserting tracer
information. (Such devices typically do not have dial-out
capabilities.)
[0087] Again, it is desirable to process the scanner or printer
data as it becomes available, so as to detect any banknote
processing with a minimum of delay. Again, there will be some lag
time before a detection decision is made. Accordingly, the scanner
or printer output will be comprised of two parts, one without the
tracer data, and another with the tracer data.
[0088] We sometimes refer to the above techniques as "Line Width
Modulation" or "LWM." And, as mentioned above, other techniques for
embedding information may include spots and holes for floods and
blank areas and directed holes.
[0089] Another technique, as disclosed in assignee's U.S. patent
application Ser. No. 10/723,181 (published as US 2004-0263911 A1)
is referred to as "Line Continuity Modulation or "LCM". This method
embeds watermarks by modulating a continuity of line structures.
For example, an auxiliary signal is embedded in a line image by
selectively breaking the lines where the embedding location value
is zero. Another example encodes watermark information by
introducing subtle modifications in a design structures to create
light and dark areas corresponding to watermark components or data
carriers.
[0090] LWM and LCM can be thought of as part of a broad class of
techniques that encode a digital watermark by modulating
characteristics of a design structure to create subtle light and
dark areas corresponding to binary 1 s and 0 s.
[0091] Additional inventive techniques and combinations are
described below.
[0092] Line Angle Modulation--Line structures often have a dominant
angle or orientation. One way of embedding watermark information is
to vary (modulate) the line angles within the design to create 0 s
and 1 s. For example, the vertical lines represent 0 s and the
horizontal lines represent is (or a distance between horizontal
lines represents data.) In another implementation a transition
between a first angle (e.g., a horizontal) and a second angle
(e.g., a vertical) conveys data. In still another implementation,
lines or graphics can be oriented with respect to a know angle of
structure provided on a document. For example, a visible fiducial
or graphic provides a base orientation through its own orientation.
Then, orientation of line structures around the document are
evaluated to determine their orientation with respect to the
visible fiducially or graphic. These techniques can be used to
embed robust watermarks. This method embeds a watermark using Line
Angle Modulation such that the watermark is preferably not visible
in the original, e.g., the line structures appear as a uniform
field in the original document. After copying, due to limitations
of the copying process, certain angles alias, and cause the
watermark to appear in the copy. An example of such a watermark is
shown in FIG. 8. A watermark
[0093] Line Frequency Modulation--A digital watermark can also be
embedded by modulating the frequency of the line structures. This
technique provides additional flexibility in tying the watermark
feature closely with the design structures. For example, for line
structures having constant width (thickness), the frequency of the
structures can be increased or decreased to embed 1 s and 0 s. The
frequency is used to convey the data.
[0094] An alternative method of using frequency modulation "warps"
or contorts an image to carry the watermark information. Consider
that a design is laid out on a stretchable surface. Now imagine
compressing the design structures in some areas and stretching the
design structures in other areas to create dense and sparse regions
respectively. Compressed regions will appear darker (more ink in
given area) while stretched regions appear lighter (less ink in
given area). This process can be used to encode watermark
information.
[0095] Line Thickness Modulation--This technique is a modification
of the LWM technique. Here, the width of each line structure, or of
a set of line structures, is maintained constant throughout its
length. However, the width of adjacent line structures are varied
to embed 0 s and 1 s. In contrast with LWM, this technique may
apply to sparser design structures.
[0096] Combination of techniques--Multiple techniques can be
combined in the design elements throughout the design depending
upon the characteristics of the design structures. These techniques
can be used to embed multiple watermarks at different resolutions
as well. For example, LCM can be used for higher resolution
watermarks whereas Line Frequency Modulation and Line Thickness
Modulation are favorable for encoding lower resolution
watermarks.
[0097] Some possible combinations of this disclosure include the
following. Of course, other combinations will be evident to those
of ordinary skill in the art. We reserve the right to present these
and other combinations as claims in this or continuing
applications.
[0098] A1. A method of watermarking an image to convey auxiliary
data, wherein the image including a plurality of line elements, the
method comprises:
[0099] determining a base line width;
[0100] varying a frequency of at least a set of line element
relative to the base line width to convey a plural-bit message.
[0101] A2. A method of watermarking an image to convey auxiliary
data, wherein the image including a plurality of elements, the
method comprises: receiving the image;
[0102] selectively contorting the image to provide relatively dense
and sparse regions of elements, wherein the dense and sparse
regions convey a plural-bit message.
[0103] A3. The method of A2, wherein said contorting comprises at
least one of resizing, scaling, stretching and warping.
[0104] A4. A method comprising:
[0105] determining a base orientation for media from a graphic or
visible fiducial; determining an orientation for a plurality of
line structures relative to the base orientation, and
[0106] deciphering a plural-bit code based on the foregoing.
Document Authentication
[0107] Cell phones continue to proliferate throughout the world's
population. Many of today's cell phones and personal digital
assistants (PDAs) are sophisticated computing devices, including
optical sensors (e.g., CCD or CMOS sensors) for image and video
capture. These optical sensors typically provide a color (or
monochrome) output. A few examples include NEC's 525 phone,
Fujitsu's F900 phone and Nokia's 3620 phone. Of course, these
examples are provided by way of example only. Many of these phones
and PDAs include robust processing and memory capability, allowing
for sophisticated signal processing (e.g., digital watermark
decoding and pattern recognition). In the case of color images or
video, the color channels include, e.g., Red, Green and Blue. The
image or video is typically displayed to a user of the device via a
display. A population, armed with these types of mobile computing
devices, have new authentication techniques available to them.
[0108] In the past, identification documents and banknotes
(sometimes referred to hereafter as "currency") have included
several lines of defensive (or authenticating) security features.
First line-security features, those that are distinguishable by
casual inspection, include optical variable devices (OVD),
including holograms, kinegrams, optical variable ink, visible or
analog watermarks, and intaglio inks. Second line-security features
are generally more covert, like digital watermarks.
[0109] The proliferation of mobile computing devices allows us to
blur these lines of defenses.
[0110] Consider an identification document that includes a
plurality of colors (e.g., via ink or dye) provided on a first
surface. One of the colors is yellow. We provide a visual graphic
in the yellow channel, e.g., like an image of an eagle or snake.
The yellow graphic is hard--but not impossible--to see with an
unaided human eye. The visual graphic might also be further
obscured by adjusting an overall luminance in an area in which the
graphic is printed by offsetting or lowering the color values of
other colors (e.g., black) in that area. Related techniques are
disclosed in assignee's U.S. Published Patent Application No. US
2002-0164052 A1 and in PCT Application No. PCT/US02/20832
(published in English as WO 03/005291). Each of these patent
documents is hereby incorporated by reference.
[0111] A consumer--armed with an imaging mobile device--captures
optical scan data representing the identification document. As
mentioned above, the mobile device includes an optical sensor that
provides a plurality of colors (e.g., RGB). The mobile device
selects the blue channel for display (or at least emphasizes the
blue channel) to the consumer. (Imaging software, e.g., products by
Adobe provided tools to allow separation of color channels. Other
software provides similar tools. Indeed, display drivers can be
programmed to selectively display a particular color channel like a
blue color channel.) The yellow channel graphic is pronounced in
the blue channel display, since the yellow color graphic results in
more light being absorbed, which is readily detectable in the blue
channel. The consumer views the graphic on her mobile display to
ascertain an authentication clue. For example, the mere presence of
the graphic provides some confidence that the identification
document is authentic. A related approach can be used with
ultraviolet or infrared inks, if the mobile optical sensor is
fitted (e.g., IR or UV filtering) to accommodate such.
[0112] Printing alignment continues to be a cornerstone in the
secure printing world. Precise or aligned printing can be used to
provide precisely located features, fine-lined graphics, etc.
Precise front to back alignment also provides authentication
clues.
[0113] An improvement is to combine aligned printing with digital
watermarking. In a first implementation, a visual feature is
provided on a surface of an identification document. The visual
feature might be obscured, as discussed above with the yellow
channel graphic. The identification document includes
steganographic encoding, perhaps in the form of digital
watermarking. The encoding includes plural-bit data. The data
carries or links to registration information associated or
cooperating with the visual feature. In a first example, the
registration information includes information to reproduce a
related feature. In this example, the first feature includes a
first geometric pattern (like a circle). The registration
information includes spatial coordinates and dimensions for a
second feature. The second feature preferably includes a second
geometric pattern (like a matching circle).
[0114] A mobile device captures optical scan data representing the
encoded identification document. Software (or dedicated circuitry)
executing on a mobile device decodes the steganographic encoding
from the captured optical scan data to obtain the registration
information. Software uses the registration information to generate
(e.g., graphically displayed relative to the image of the first
feature) the second geometric pattern and align it for display on
the mobile device. In some cases the first and second patterns are
intended to overlap or intertwine in an expected manner
Misalignment or mis-registration relative to the first feature
indicates a potential counterfeit.
[0115] (Unless extreme care is taken with the printing of the first
feature--and corresponding alignment of the second feature--the
expected alignment of the first and second features may be
spatially mis-registered. We note here that alignment and
registration of the second feature may be eased with pattern
recognition software. For example, the pattern recognition software
identifies the first feature based on its shape (or pattern). A
placement location of the second feature can be based on a location
of the first feature, once found. Edge detection software can also
be used to determine a location of the first feature. An edge of
the document or feature can be used to identify a location. If a
counterfeiter makes the first feature too small, or offsets the
first feature, the rendering of the second feature will not
correspond as expected. Of course, we can use a registration
component carried by steganographic encoding to resize, translate
or rotate the captured imagery if needed.)
[0116] In some cases, the first feature is laid down on a substrate
using a first printing plate (and color), while the steganographic
encoding is laid down on the substrate using a second printing
plate (and color). In the first example discussed above,
registration or alignment between the two printing plates provides
additional security, since alignment is required in order to
properly generate a second feature relative to the first
feature.
[0117] Another example uses printing alignment of a front surface
and a back surface. Consider the document in FIGS. 9a and 9b. FIG.
9a shows a first surface (e.g., front surface) of an identification
document. The document includes a first window. The window may
include a transparent or semi-transparent polymer or may include a
pressed area (e.g., pressed paper) to provide some transparency,
perhaps aided by a light source. The first surface window may
include a graphic, image, texturing or background printing. The
graphic, image, texturing or background printing includes first
steganographic encoding.
[0118] FIG. 9b shows a second surface (e.g., back surface) of the
identification document. The window is seen on the second surface
as well. The second surface window may include a graphic, image,
texturing or background printing. The graphic, image, texturing or
background printing includes second steganographic encoding.
[0119] The first and second steganographic encodings cooperate to
provide an authentication clue.
[0120] For example, a mobile device captures an image of the window
from either a viewpoint of the first or second surface. Since the
window is transparent or semi-transparent, both the first and
second stegangraphic encoding is optically captured with a
single-sided scan of the window. The spatial relation of the first
and second steganographic encoding can be used to determine whether
the document was properly registered when originally printed.
Mis-registration signals a potential counterfeit document.
[0121] The first and second steganographic encoding can cooperate
in other ways as well. For example, the first steganographic
encoding may include a plural-bit payload that indicates a relative
and expected spatial location of the second steganographic
encoding.
[0122] The scale, rotation and/or translation of the first and
second steganographic encoding, relative to each other, is another
indication of original printing misalignment (a telltale sign of a
counterfeited document). Watermark orientation parameters are even
further discussed, e.g., in assignee's U.S. Pat. Nos. 6,614,914,
6,704,869 and 6,385,329, which are each hereby incorporated by
reference.
[0123] Of course, plural-bit payloads, each carried by the first
and second steganographic encoding can be redundant or
cross-correlated for authentication.
[0124] Digital watermarking can also be used to provide anonymity
for currency substitutes. We envision users to one-day print cash
substitutes at home, at mall kiosks or on the road.
[0125] Digital watermarks are used in these situations to provide
related information. A digital watermark may include a message or
payload that is used to indicate a "one-use" only requirement. The
message, once decoded, is used to interrogate a data structure
which keeps track of whether the cash substitute has ever been used
before. The watermark may also include a "good-until" indicator,
issuing authority, amount, etc.
[0126] Some possible combinations of this disclosure include the
following. Of course, other combinations will be evident to those
of ordinary skill in the art. We reserve the right to present these
and other combinations as claims in this or continuing
applications.
[0127] B1. An identification document or banknote comprising:
[0128] a substrate including a first surface and a second
surface;
[0129] a transparent or semi-transparent window disposed in the
substrate, wherein the window is viewable from both the first
surface and the second surface,
[0130] first steganographic encoding on the first surface window
side; and
[0131] second steganographic encoding on the second surface window
side.
[0132] B2. The document or banknote of B1, wherein the first
steganographic encoding and the second steganographic encoding
cooperate to yield authentication clues.
[0133] B3. The document or banknote of B2, wherein the cooperation
provides a relative spatial alignment of the first steganographic
encoding and the second steganographic encoding.
[0134] B4. The document or banknote of B3, wherein the relative
spatial alignment of the first steganographic encoding and the
second steganographic encoding comprises at least one of rotation,
scale and translation.
[0135] B5. The document or banknote of any one of B1-B4, wherein
the first steganographic encoding comprises a first plural-bit
message and the second steganographic encoding comprises a second
plural-bit message, and wherein the cooperation comprises a
redundancy or cross-correlation of the first and second
messages.
[0136] B6. The document or banknote of any one of B1-B4, wherein
the first steganographic encoding and the second steganographic
encoding are both detectable from a single optical scan of either
the first surface or second surface.
[0137] B7. The document or banknote of any one of B1-B6, wherein
the substrate comprises a first material and the window comprises a
second, different material.
[0138] B8. The document or banknote of B7, wherein the first
material comprises paper or a paper synthetic.
[0139] B9. The document or banknote of B7 or B8, wherein the second
material comprises a plastic or polymer.
[0140] C1. A banknote or identification document comprising:
[0141] a substrate;
[0142] multi-color printing on the substrate, wherein the
multi-color printing includes a first feature printed therein in a
yellow color, wherein the yellow color first feature is obscured to
an unaided human eye.
[0143] C2. A method of analyzing the banknote or identification
document of C1 with a handheld computing device, wherein the
handheld computing device comprises at least an optical sensor,
electronic processing circuitry and a display, said method
comprising:
[0144] receiving optical scan data of the banknote or
identification document from the optical sensor;
[0145] providing blue channel color information for display on the
display, wherein the first feature is readily perceptible on the
display to an unaided human eye.
[0146] C3. The method of C2, wherein the device comprises a cell
phone or personal digital assistant.
[0147] C4. The method of any one of C2 and C3, wherein the banknote
or identification document comprises steganographic indicia encoded
therein.
[0148] C5. The method of C4, wherein the steganographic indicia
comprises registration data.
[0149] C6. The method of C5, wherein the registration data
comprises or links to a second feature.
[0150] C7. The method of C6, wherein the device comprises
instructions for execution on the electronic processing circuitry
to: i) recognize the first feature; ii) generate for display on the
display the second feature at an alignment relative to the first
feature.
[0151] C8. The method of any one of C1-C7 wherein only blue channel
color information is provided for display on the display.
[0152] C9. The method of any one of C1-C7 wherein the blue channel
color information is emphasized relative to other color information
when displayed.
[0153] Metallic Inks
[0154] Specialized, metallic inks have emerged which allow
electronic circuitry (e.g., RFIDs) to be "printed" on document
substrates.
[0155] Some examples of electronic circuitry are shown, e.g., in
assignee's U.S. Pat. No. 6,608,911 and published U.S. patent
application Ser. No. US 2003-0178495 A1 (allowed). Each of these
documents is herein incorporated by reference.
[0156] One improvement embeds a digital watermark in a circuit
layout itself. Subtle changes to line widths or ink contrast are
employed in the circuit layout when it is printed, laid down,
etched, or fabricated. For example, the line modulation techniques
disclosed herein may be used to encode a watermark signal in a
circuit layout. The subtle changes convey a digital watermark,
which is detectable through optical scan data of the circuit. Even
a circuit diagram can include the watermark embedded therein.
Imagine a product label or product packaging that is printed with
an RFID metallic ink layer. The layer is optically scanned and the
watermark is discerned there from.
[0157] Identification documents and banknotes may include
electronic circuitry. The circuitry may be passive, in that it
requires an external energy or frequency source to excite the
circuitry. The circuitry may be responsive at any desired frequency
(e.g., even extending into the high Gigahertz range). The circuitry
may include a variety of elements like miniature light emitting
diodes and piezoelectronic or audio devices.
[0158] When excited by an appropriate stimulus (e.g., exposure to a
particular energy or transmission frequency) the electronic
circuitry is energized. In a first example, the identification
document or banknote "shines" via the LED. The shinning provides an
authentication clue. In a second example, the identification
document or banknote vibrates via a miniature piezoelectronic
transducer upon exposure to an appropriate stimulus. In a third
example, the identification document or banknote emits an audible
sound via a miniature piezo-audio device upon exposure to an
appropriate stimulus. In a fourth example, a digital watermark
carried by the identification document or banknote includes a key
or seed value. The key or seed value, once decoded from the digital
watermark, is used to tune the external stimulus to a particular
frequency or setting. Once tuned, the stimulus excites or energizes
the electronic circuitry.
[0159] In a related implementation, an identification document or
banknote includes passive (or active) electronic circuitry. The
electronic circuitry emits (perhaps only after external
stimulation) a first frequency. A reader emits a second frequency,
and employs a heterodyning process to generate a third frequency
based on the first and second frequencies. The third frequency is
used to determine authenticity of the document or banknote. In some
implementations, the first frequency emitted by the electronic
circuitry is used as a key or seed, which is used to select an
appropriate second frequency for the heterodyning process.
[0160] Some possible combinations of this disclosure include the
following. Of course, other combinations will be evident to those
of ordinary skill in the art. We reserve the right to present these
combinations as claims in this or continuing applications.
[0161] D1. A banknote comprising:
[0162] a substrate;
[0163] printing on the substrate; and
[0164] electronic circuitry carried on or in the substrate, wherein
the electronic circuitry is passive and activates in response to a
predetermined energy or frequency.
[0165] D2. The banknote of D1, wherein the electronic circuitry
includes a piezo-electronic device.
[0166] D3. The banknote of D2, wherein the piezo-electronic device
vibrates when the electronic circuitry is activated in response to
the predetermined energy or frequency, the vibration providing a
sensory authentication clue.
[0167] D4. The banknote of D2, wherein the piezo-electronic device
emits an audible sound when the electronic circuitry is activated
in response to the predetermined energy or frequency, the sound
providing an audible authentication clue.
[0168] D5. The banknote of D1, wherein the electronic circuitry
comprises a light emitting element which is activated in response
to the predetermined energy or frequency, the activated light
emitting element comprising a visual authentication clue.
[0169] D6. A reader cooperating with the banknote of any one of
D1-D5, comprising:
[0170] an energy or frequency source;
[0171] a receiver to receive a first frequency emitted by the
electronic circuitry;
[0172] a determination module to determine whether a frequency
corresponds to an expected frequency, and if so, to provide a
signal indicating such determination.
[0173] D7. The reader of D6, wherein the energy or frequency source
excites the electronic circuitry.
[0174] D8. The reader of D6, wherein the energy or frequency source
emits a second frequency, and wherein the determination module
heterodynes the first and second frequencies to yield a third
frequency, wherein the third frequency compared for correspondence
to the expected frequency.
[0175] D9. A method comprising:
[0176] providing an electronic circuit on a surface through
metallic ink, wherein the electronic circuit yields a plural-bit
identifier when excited, and wherein the electronic circuit is
provide so that an optical scan of the electronic circuit will
yield a steganographic signal.
[0177] D10. The method of D9, wherein the steganographic signal is
provided through subtle changes to lines of the electronic
circuit.
[0178] D11. The method of D11 wherein the steganographic signal
comprise plural-bit data.
[0179] D12. The method of any one of D9-D11 wherein the plural-bit
identifier and the plural-bit signal coincide.
[0180] D13. The method of any one of D9-D12 wherein the electronic
circuit comprises an RFID.
[0181] Now with reference to FIG. 10, we detail a relationship
between cash and consumer confidence. We refer to this figure as a
"dumbbell" model. One the left side, cash (or money) is represented
both in the physical world (e.g., paper banknotes and checks, etc.)
and electronic or cyber world (e.g., digital cash and financial
records/credit). The left side of the dumbbell is balanced by
confidence and brand protection on the right side. In order for the
cash to have any meaningful significance, a consuming base must
believe or have confidence in the physical or electronic
manifestation of the currency. An example is currency brand.
Historically the US currency has been a strong "brand" of
currency.
[0182] Digital watermarks are used to support the FIG. 10 model.
For example, a digital watermark is used to bridge the gap between
physical and electronic cash. A unique identifier is associated
with an account or "credit". The watermark or unique identifier is
associated with the electronic cash, and is conveyed when the
credit is converted to a physical form. The watermark is used for
authentication, as discussed above.
Security through Metameric Ink Pairs
Inks and Dyes
[0183] A first embodiment of this aspect of the present disclosure
employs a pair of similarly colored inks or dyes. For example,
these inks may be termed so-called "metameric" inks.
[0184] Metameric inks work on a principle of metamerism; that is,
two colors matching or approximating one another under one set of
conditions can appear or behave quite differently under another set
of conditions.
[0185] We preferably employ a pair of metameric inks that appear
(visually) about the same under normal or visible lighting
conditions. The term "about" in this application takes on its
typical meaning of "approximately," "similar" or "close to,"
etc.
[0186] The inks differ, however, in that one ink in the ink pair is
a metallic ink. The metallic ink includes metal pigments, platelets
or other portions that provide the ink with metallic
characteristics (e.g., radiation reflectance).
Arrangement on a Surface
[0187] We arrange a pair of metameric inks on a first surface 12
(FIG. 11) of an identification or security document 10 to achieve
at least two goals: 1) visual obfuscation of a metal ink; and ii)
creation of a diffraction grating on the first surface via the
metallic ink. Our use of the terms "diffraction grating" envisions
a grating or pattern that can at least "reflect" or "diffract"
energy or radiation. (We sometimes refer to a diffraction grating
or pattern as a "metal grating," "reflection pattern" or
"reflection grating.")
[0188] FIG. 11A illustrates a portion of the first surface 12. An
ink pair is provided in a pattern. As illustrated, the pattern
includes a line art image (e.g., such as are sometimes used in
security documents, graphics, identification documents and the
like). Of course, our techniques are not limited to line art images
and can be employed in many other graphics, images and patterns as
well.
[0189] The ink pair, Blue (B) and Metallic Blue (MB), is arranged
as shown in FIG. 11A. The Blue ink (B) and the Metallic Blue ink
(MB) are arranged to form continuous lines on a surface. The lines
appear continuous and about the same color (or at least very
similar in color) to a casual human observer of the surface (FIG.
12). This similar appearance results since the Blue (B) ink and
Metallic Blue (MB) ink are a metameric pair. A casual human
observer is preferably not aware of the location of the metal
ink--meeting goal no. 1 above. (We note that many ink and dye
manufactures, e.g., including Pantone, Inc., with a North American
office in Carlstadt, N.J. USA, provide matching metallic and
non-metallic inks.)
[0190] The Blue (B) and Metallic Blue (MB) inks transition at
position 20 as shown in FIG. 11A. Since some metallic inks have a
"shine" or "luster," human observation of the transition 20 can be
lessened by providing thin lines. In other embodiments, we provide
lines or shapes in a dot matrix-like fashion. In those embodiments,
we can overprint the Blue (B) ink into the Metallic Blue (MB)
regions to lessen a stark transition.
[0191] The inks can be arranged in accordance with, e.g., known
printing processes. In a preferred implementation, however, we
employ a printing process including at least two printing plates. A
first plate prints the Blue (B) ink and a second plate prints the
Metallic Blue (MB) ink. Tight plate registration is preferred to
achieve visually continuous patterns as shown in FIG. 11A. (We note
that high end printing presses, like those used for printing
security documents like currency, provide exceptional plate
registration capabilities.) Of course other printing techniques can
be used so long as sufficient printing registration of the
non-metallic ink and the metallic ink is maintained.
[0192] With reference to FIG. 13, a Metallic Blue (MB) ink is
provided to yield a reflection pattern (or diffraction grating).
That is, the Metallic Blue (MB) ink includes reflective properties
that, when arranged in a pattern on first surface 12, provide a
diffraction grating capable of reflecting or diffracting high
frequency radiation or illumination. A portion of the grating is
shown with bolded Metallic Blue (MB) sections in FIG. 13. The
illustration deemphasizes (shown with dashes) the non-metallic Blue
(B) ink since Blue (B) ink lacks any significant contribution to
the metal grating. The diffraction grating is designed to yield a
desired frequency response (or reflection pattern) when illuminated
with an energy or radiation source.
[0193] Some care is preferably taken when designing a diffraction
grating.
[0194] In a first situation, where a designer has somewhat
unfettered design discretion, a diffraction pattern is laid out
(perhaps computer-assisted to achieve a particular reflection
pattern, as is common nowadays), and then an obfuscation pattern is
formed around the diffraction grating. For example, Metallic Blue
(MB) ink is mapped to the diffraction grating design, and then Blue
(B) ink is provided in concert with the Metallic Blue (MB) ink to
form a visual design that helps conceal the location of the
Metallic Blue (MB) ink.
[0195] In a second, perhaps more common situation, a host or
carrier image is provided. For an identification document, the host
image may include, e.g., a state seal or graphic, and for a
security document, the host image may include, e.g., a bank logo,
line-art or background pattern. Using the host image as a template,
a diffraction grating is designed to blend within the host
image--sometimes this process is referred to as generating an
"interference" or "composite" image. The interference or composite
image represents both the host image and the diffraction grating.
If the host image includes line art, line segments are identified
to host metallic ink that will form a diffraction grating. If the
host image includes an image or graphic, regions within the image
are identified to receive grating portions.
[0196] A shading or tinting effect might be added to a host image,
where the shading or tinting comprises a plurality of parallel or
smoothly curving lines provided with metallic ink. Such shading
hosts the diffraction grating. A host image can also be filled in
or created with "dots" or "blobs" where a set of the dots or blobs
include fine lines or areas provided with metallic ink (FIG. 11D).
The set of dots or blobs collectively provide a diffraction
grating. Non-metallic ink dots or blobs can be intertwined with
their metallic cousins to obfuscate the location of the metal
dots--and consequently the location and design of the diffraction
grating. (More generally, metallic dots can be laid down to provide
a diffraction grating on a surface of a security or identification
document.)
[0197] Regardless of the technique used, identified areas of a
diffraction grating are used to guide metallic ink placement.
[0198] Line spacing for a diffraction grating is preferably
determined with consideration of the illumination source (e.g.,
60-75 GHz), so that the grating can accommodate the radiation or
illumination wavelengths and provide a desired reflection beam or
pattern response. We prefer that our lines be on the order of about
a millimeter or less, but other dimensions can be used according to
a given design criteria. Distance between lines or dots can be
adjusted to accommodate a desired reflection response, as is known
to those of ordinary skill in the art.
[0199] In some implementations we use a pseudo-randomly generated
spatial pattern to help identify locations for placing metallic
ink. Once locations are identified, metallic ink is laid down to
provide a reflectance pattern. A key (perhaps assigned to an
issuing authority) can be used to seed a pseudo-random pattern
generator.
[0200] Still other examples of arranging ink pairs are shown in
FIGS. 11B and 11C. FIG. 11B shows parallel lines, resulting in a
somewhat typical diffraction grating formation. The straight lines
contrast to the curvilinear grating shown in FIG. 11A. FIG. 11C
illustrates Metallic Blue (MB) ink that is over-printed or printed
adjacent to selected segments of Blue (B) ink. This technique lays
down a thin line or shadow at selected areas. This technique can be
advantageously used to obfuscate locations of the Metallic Blue
(MB) ink as well.
[0201] Of course there are still many other arrangements that can
be made to visually obscure a metal ink while providing a
diffraction grating. We note that some implementations will have a
transition area between first and second inks. This transition area
allows for a gradual change between first ink and the second ink,
which will help if inks noticeably differ in color or sheen.
Excitation or Energy Source
[0202] An excitation source excites the diffraction grating, e.g.,
excites the Metallic Blue (MB) ink, as seen in FIG. 14. An
excitation source (e.g., transceiver 40) preferably illuminates in
the range of 50-80 Gigahertz, but most preferably in the range of
60-75 Gigahertz. The source can be accommodated in a handheld
device (e.g., a keychain FOB, adapted cell phone, or the like) or
mounted at a stationary location (e.g., point of sale
location).
[0203] In a first implementation the excitation source 40 emits a
burst (or chirp) at a predetermined frequency (e.g., 72 Gigahertz).
The diffraction grating or pattern (metallic ink) reflects the
energy in a pattern in accordance with its design.
[0204] In a second implementation the energy sources emits a chirp
or burst that cycles through a range of frequencies (e.g., ramps up
from 60 GHz to 75 GHz, and then perhaps back down to 60 GHz again).
The chirp signal reflects from the diffraction grating or pattern
in accordance with the grating's pattern.
[0205] Illumination and resulting reflectance is shown, albeit in a
simplified manner, in FIG. 14. Transmitted radiation (or energy) is
shown with solid lines and reflected radiation is shown in
returning hashed lines.
[0206] The excitation source includes a receiver, perhaps even a
MIMO (multiple inputs, multiple outputs) or SIMO (single input,
multiple outputs) receiver, which includes multiple transmitters
and receptors.
[0207] An authenticator module 45 (FIG. 14) determines a signature
from reflected radiation patterns (e.g., reflection or beam
patterns or a plurality of "peaks" representing reflection angles
or phase relationships, etc.) over the cycled frequency range or a
reflection pattern corresponding to a single reflection. The
signature need not include all features from a reflected pattern,
but instead may include one or more attributes of a received
reflectance pattern. If using multiple transmitters and/or
receivers, a signature may contemplate received interference
patterns as well. The authenticator module 45 determines whether
the signature matches (or coincides within a predetermined
tolerance) an expected signature.
[0208] Different organizations (e.g., different states when issuing
driver's licenses) can each be assigned a unique signature (and
corresponding grating pattern). Different types of documents can be
similarly distinguished (e.g., a first signature for a passport,
and a second different signature for a visa, or a first signature
for a first denomination of currency and a second different
signature for a second denomination of currency).
[0209] The authenticator module 45 may cycle through a list of
expected patterns to determine whether a received pattern matches
at least one of the expected patterns.
[0210] The identification document or security document is
authenticated when a signature matches (or coincides within a
predetermined tolerance) an expected pattern or signal. The
document is considered suspect absent such a match.
Combined with Watermarking
[0211] In some cases we prefer a subtle color or contrast variance
between the first ink and the metallic ink. The color or contrast
variance is slight so as to be generally unnoticeable by a casual
human observer. The metallic and non-metallic inks are arranged to
provide both a diffraction grating and a digital watermark.
[0212] For example, Line Width Modulation techniques (LWM) or Line
Continuity Modulation (LCM) techniques can be used to pattern a
digital watermark (see, e.g., Published Application No. US
2005-0041835 A1 and U.S. Pat. No. 6,449,377).
[0213] The digital watermark pattern can be considered when
designing a diffraction grating. (Redundant encoding and error
correction encoding can help ensure that both a watermark signal
and a diffraction grating are sufficiently produced.) Thus, an
identification document includes both a watermark (observable from
scan data) and a diffraction grating (verified through received
radiation patterns) conveyed through the same pair of inks.
Organic Light Emitting Diodes
[0214] Organic polymers and other materials have recently led to
the commercial viability of so-called "organic light emitting
diodes" or "OLED" display (or "array" or "matrix"). OLEDs and
methods of manufacturing such are further discussed, e.g., in U.S.
Pat. Nos. 6,664,564, 6,670,052, 6,774,392 and 6,794,676, which are
each hereby incorporated by reference.
[0215] An improvement is to provide an OLED display on an
identification document or banknote.
[0216] One can imagine the possibilities. An OLED display can
provided a luminous pattern, perhaps to show an expected currency
denomination (e.g., text or number) or identification document
type, or a graphic or seal. The displayed graphic or seal may
include a hidden signal, e.g., a digital watermark embedded
therein. An optical scan of the OLED will include the hidden signal
embedded in the graphic or seal.
[0217] With the aid of micro-circuitry, the luminous pattern can
change. That is, the pattern can alternate between different
patterns, or between text and patterns, etc.
[0218] The OLED display is provided on or in a first area of the
document or banknote. In some implementations, but certainly not
required, the first area is a see-through, thin plastic window. The
OLED display can be activated with an on-document power supply,
e.g., a micro battery. In other implementations, the document or
banknote includes piezoelectric device(s). Friction or movement of
the document or banknote activates the piezoelectric devices, which
creates a current to activate the OLED display. In still other
implementations, the OLED display includes or cooperates with
passive circuitry; that is, circuitry that generates or responds to
an electric field. The current is provided to the OLED display for
activation. In still other implementations, a document or banknote
includes a contact, and power is transferred to the document or
banknote through the contact. Another possible power source is
solar energy or other light source.
[0219] Related to the above discussion, in other implementations
polymer thin film electronics are provided to create a layer of
plastic with an array of transistors and LEDs across the surface of
a film. The film layer is integrated within a document structure
(e.g., laminate onto core layer, for example). The circuitry can be
driven with a power supply, e.g., an on-document supply, such as a
battery, or a contact or interface that receives power from an
external power source. In either case the power energizes the LED
array. The LED array can be used to display information, e.g.,
including information stored in the document (biometric
information, demographic information, etc.). This is easy to
imagine when the document includes electronic memory circuitry,
e.g., such as is provided by a so-called smart card. Information
from the memory circuitry is communicated to the LED array for
display. But even paper thin documents, e.g., banknotes, can carry
information. A series of transistors (e.g., organic TFT) are
provided on the document, or in a layer of the document. The
transistors form a memory cell, which can include information like
a serial number, denomination, or hash of information printed on
the document.
[0220] Information carried by the document or banknote can interact
with external information supplied to the document through an
interface. Consider a document that includes a wireless interface.
The document receives information through the interface. In some
implementations the information is a key (e.g., of a key pair) that
decrypts information encrypted on the card with the other key of
the pair (e.g., a private/public key pair). The decrypted
information is displayed via the LED array. If the information is
legible or expected the document is considered authentic, otherwise
the document is considered suspect.
[0221] Of course, this technology has application in a wide variety
of secure documents, including bank cards, financial instruments,
bank notes, cards and documents, etc.
[0222] Some possible combinations of this disclosure include the
following. Of course, other combinations will be evident to those
of ordinary skill in the art. We reserve the right to present these
and other combinations as claims in this or continuing
applications.
[0223] E1. A financial instrument or identification document
comprising:
[0224] a substrate;
[0225] a power supply carried on or in the substrate;
[0226] electronic circuitry carried on or in the substrate; and
[0227] an organic light emitting diode (OLED) display carried on or
in the substrate and powered by the power supply and controlled or
driven, at least in part, by the electronic circuitry.
[0228] E2. The financial instrument or identification document of
El, wherein the power supply comprises at least one of a battery, a
passive-current generating device, solar or light conversion cell,
and a piezoelectric device.
[0229] E3. The financial instrument or identification document of
E1, wherein the electronic circuitry comprises memory with first
information stored therein.
[0230] E4. The financial instrument or identification document of
E3, wherein at least some of the first information is communicated
to the OLED display via the electric circuitry for display
thereon.
[0231] E5. The financial instrument or identification document of
E4, wherein the at least some of the first information that is
communicated to the OLED display comprises at least one of a
currency denomination, a graphic, seal, text, and number.
[0232] E6. The financial instrument or identification document of
E4 wherein the at least some of the first information that is
communicated to the OLED display comprises first display
information and second display information, wherein the electronic
circuitry provides timing of the first display information and the
second display information so that the first display information is
first displayed by the OLED display and then the second display
information is displayed by the OLED display.
[0233] E7. The financial instrument or identification document of
any one of E1-E6 wherein the instrument comprises at least one of a
banknote, currency, check, note, draft, traveler's check, security
interest, bond and certificate.
[0234] E8. An identification document comprising:
[0235] a substrate;
[0236] a power supply carried on or in the substrate;
[0237] electronic circuitry carried on or in the substrate; and
[0238] a light emitting diode (LED) matrix carried on or in the
substrate and powered by the power supply and controlled or driven,
at least in part, by the electronic circuitry.
[0239] E9. The identification document of E8 wherein the electronic
circuitry comprises polymer-based thin film electronics.
[0240] E10. The identification document of E8 wherein the
electronic circuitry and LED matrix are carried by a thin film
layer carried by the substrate.
[0241] E11. The identification document of E10 wherein the thin
film layer is laminated to the substrate.
[0242] E12. The financial instrument or identification document of
E3, wherein the first information comprises an encrypted form.
[0243] E13. The financial instrument or identification document of
E12, wherein the document or instrument further comprises an
interface to receive second information.
[0244] E14. The financial instrument or identification document of
E13, wherein the second information comprises a key to decrypt the
first information prior to display on the LED display.
[0245] E15. The financial instrument or identification document of
E3 wherein the substrate comprises at least one of printing,
engraving and a photograph, and the first information comprises
information that corresponds to or is redundant with the printing,
engraving and photograph.
[0246] E16. The financial instrument or identification document of
E15 wherein the substrate comprises multiple, separate layers.
[0247] E17. The financial instrument or identification document of
any one of E1-E7 and E12-E16, wherein the instrument or document
comprises at least one of a banknote, currency, check, note, draft,
traveler's check, security interest, bond and certificate, driver's
license, passport, visa and national id.
Interference of Thin Films
[0248] A phenomenon of light interference in thin films (e.g.,
think of soapy water) is well understood and has been leveraged to
create a broad array of security features since copying or altering
objects with these types of "light interference" features is
difficult.
[0249] Constructive and destructive interference of light due to
internal reflection at a boundary of the thin film creates a
desired effect of shifting spectral reflection as a function of
several different parameters, most notably an "angle of
incidence."
[0250] A simple example of this effect is shifting of spectral
reflection of soapy water from a center point of 536 nm to 455 nm
when the angle of incidence moves from normal to 45 degrees.
[0251] This property of shifting spectral reflection can be used to
create a digital watermark that can only be observed by viewing a
watermarked image at an angle off normal (see FIG. 18). The
modulation in spectral response (e.g., the watermark itself) is
created by varying a thickness of the film, which can be
accomplished by any number of techniques including screening of the
image (assuming it is being printed with pearlescent ink that
displays these properties) or the film itself can be produced to
vary in thickness.
[0252] To recover the watermark, the document is illuminated with
white light and viewed at the specified angle. The recover process
can be augmented by using an equivalent of, e.g., a notch-filter or
with illumination of a specific wavelength (e.g., truncating higher
spectral frequencies, with reference to the dashed line in FIG.
18).
[0253] The techniques centered on a single film can be easily
extended to multiple films that are stacked to create much larger
shifts in spectral response.
[0254] In another embodiment, this increase in spectral shifts,
combined with more complex behaviors, can be used to impart a
number of different behaviors on a watermark itself. For example:
[0255] Increased Fragility: Frequency band where a watermark
appears is tightly controlled, such that only with very narrow-band
illumination or with a notch filter can the watermark be read.
[0256] Tamper Evidence: By imparting fragility in the structure
itself (e.g., varying the adhesives between films) a watermark is
designed such that a component of the watermark is carried in the
fragile film, such that if the document is tampered with and the
film was separated, the watermark would no longer read. A variant
of this is having a watermark appear if tampering occurs. This can
be abstracted to create a system wherein integrity of a thin-film
based security feature can validated in an automated fashion, layer
by layer. [0257] Interdependence: Similar to physical security, a
watermark can only be read by knowing the "recipe" of where and how
to illuminate a structure to recover the watermark. This recipe may
include multiple observation points, illumination sources and
filtering. All requiring that all the observed spectral shifts are
co-located such that the watermark is still readable (e.g., think
of plate-registration, but taken to three dimensions. Each layer
must be registered (X,Y) and the thickness has to be correct (Z)).
[0258] Appearance of disappearance of wave-bands: In another
embodiment, a perceived double to single waveband shift (e.g., both
spectral responses shift, but one might shift into UV, hence making
it non-visible) is used to weaken or allow a watermark to
appear.
Retroreflection
[0259] Retroreflection as phenomena has been leverage from security
applications (e.g., 3M's Confirm laminate) for safety clothing
(e.g., a reflective vest for running at night). The angle of
reflection and spectral response can now be controlled through
various manufacturing processes.
[0260] Through the modulation of both of these parameters (i.e.,
angle of reflection and spectral response, as well as other
parameters) a watermark can be encoded in retroreflective material.
Similar to the prior embodiment using thin films, the watermark
appears, disappears or changes (including yielding a different
payload at different observation angles) as a function of the
observed angle.
WORM Watermark
[0261] Prior to the mass availability of CD Burners and acceptance
of such into the common vernacular (to "burn" something means the
permanent writing of) this functionality was referred to as Write
Once Read Many (i.e., "WORM"). Many embodiments of this existed,
where only portions of the disk were writeable, etc.
[0262] A digital watermark equivalent is one that allows its
payload (e.g., plural-bit message) to be encoded and embedded and
then altered in the field after a watermarked image is produced on
a substrate.
[0263] For example: [0264] Encode watermark template in a
substrate, but add/modify message to the substrate after production
by using techniques such as is used in DCards, where the substrate
itself is heated locally and causes a "browning" of the PVC
substrate where heated. [0265] Destroy specific "cells" within
retro-reflective laminate to locally change the spectral response
when viewed at a specific angle.
[0266] For statistics-based encoding or decoding, remarking
"resets" the statistics of the image, so that the image can be
re-marked. Remarking does have visual impacts though, so only a
limited number of overwrites are currently possible.
Physical Random Functions in Security Printing
[0267] Advances in digital imaging and printing technologies have
vastly improved desktop publishing, yet have provided
counterfeiters with low cost technologies for illegally
counterfeiting security documents (e.g., banknotes, checks, notes,
drafts, and other financial instruments) and identification
documents (e.g., driver's licenses, passports, ID documents, visa,
etc.). While there are many technologies that make counterfeiting
more difficult, there is a need for technologies that can quickly
and accurately detect originals and distinguish copies. Preferably,
these technologies integrate with existing processes for handling
such documents.
[0268] By way of some additional background, and with reference to
the semiconductor world, we often find naturally occurring
variances in circuit manufacturing. For example, doping levels of
production materials (e.g., semi-conductors) slightly vary from
device to device. These slight variations have been leveraged to
create addressable logic, and are sometimes referred to as
"Physical Random Functions" (or "PRFs" or "PUFs").
[0269] This addressable logic (or, more generally, the device's
unique variations) are used to uniquely identify a specific
circuit, used as a seed for a random number generator and even used
as a key for a cryptographic process. One advantage of Physical
Random Functions is that they are based on what is believed to be
fundamentally random process that is hard to control or predict;
hence, the random features are hard to counterfeit.
[0270] Many printing process have a number of PRFs as well. The
variations or functions have been used in forensic analysis of
documents and to identify types of printers. See, e.g.,
Mikkilineni, et al., "Printer identification based on graylevel
co-occurrence features for security and forensic applications," in
Security, Steganography, and Watermarking of Multimedia Contents
VII, edited by Edward J. Delp III, Ping Wah Wong, Proceedings of
the SPIE-IS&T Electronic Imaging, SPIE Vol. 5681, pages 430-440
(2005), which is herein incorporated by reference. Such variations
or functions might include plate registration, ink density, dot
gain, printer characteristics, and other printing characteristics.
For inkjet or toner based systems, variations or distinctive
patterns in ink/toner spray, banding artifacts or drop-outs can be
identified.
[0271] We extend the use of PRF features to create a
machine-readable (or at least a machine-observable) feature that
can be read in an automated fashion for printed security and
identification documents.
[0272] One implementation relies on a random placement of so-called
security fibers during security document manufacture. Security
paper fibers are sometimes mixed in with raw paper pulp during
paper manufacture. Some times the paper pulp is a cotton and linen
concoction. (For identification documents, fibers or fluorescent
particles can be mixed in a document substrate or layer during,
e.g., a molding process.) Some currencies leverage color fibers
(some of which are UV sensitive) in their paper making process,
see, e.g., the Crane & Co. paper. Due to the introduction of
the fibers in the paper pulp, the fibers are lodged in the
substrate as opposed to being on the surface. The fiber's placement
within the substrate protects them from undue soiling and wear. An
exaggerated example of such fibers in a document is shown in FIG.
15. These fibers find themselves arranged in a security document in
a random manner--akin to Physical Random Functions seen in
semiconductor devices.
[0273] The random arrangement of such fibers allows for a
calculation of a unique signature or fingerprint based on the
fibers. Such features can be observed with an optical imager (e.g.,
optical scanner or cell phone camera) or some other instrument
typically used in the field (e.g., magnetic head for magnetic
characteristics, IR or UV camera for out-of-visible spectrum
characteristics, etc.). The signature or fingerprint can include a
representation of a spatial relationship of all fibers or a set of
fibers. This representation, once determined, can be used to seed a
number generator or hashing algorithm. The resulting number is the
unique identifier. Or a slope of one or more of the security fibers
can be calculated and used as an identifier; related is a
calculation of a second derivative for one or more of the fiber's
shape (or slope curvature). The result is used as an identifier or
as a seed to a number generator or hashing algorithm Of course
other identifying techniques based on the security fibers can be
used as well.
[0274] The result of such calculations is an identifier that
uniquely represents a security document based on the PRF nature of
the security fibers.
[0275] Applications of PRF's
[0276] One application using PRFs is tracking and monitoring.
Documents are monitored as they flow through distribution centers.
An optical scanner scans each document (or a sampling of such
documents) as the documents flow by. The optical scan data is
analyzed by a monitor (e.g., software or hardware monitor) to
calculate unique identifiers for the respective documents.
[0277] One can imagine a counterfeiting scenario that includes
copying one document and reproducing it time and time again. (The
fibers are represented with color ink in the copies. Each copy will
then have the same PRF characteristic as its parent document.) If a
monitor recognizes the same or statistically similar identifiers
time and time again, the monitor can issue an alert for an emerging
counterfeiting threat.
[0278] PRF's combined with other machine readable features
[0279] As discussed above, a PRF can be used to create a unique
identifier for a document (e.g., a 256-bit identifier). A unique
identifier can be used in cooperation with digital watermarking and
other machine-readable indicia.
[0280] For example, a digital watermark embedded in a document may
carry a number resulting from PRF analysis.
[0281] (Behind the scenes, a PRF is read from an unprinted document
substrate, e.g., via optical scanning of the substrate. Resulting
optical scan data is analyzed and a unique identifier based on the
PRFs is generated there from. The unique identifier is provided to
an embedder. The embedder embeds the unique identifier as, e.g., a
digital watermark or overt 2-D symbology. The watermarking or
symbology is provided on the document during printing.)
[0282] In another, related embodiment, a document is modified each
time it is inspected and validated. For example, a document is
modified in some machine-recognizable fashion each time the
document passes through a centralized facility. A document can be
subtly reprinted to include another machine-readable component
(e.g., a digital watermark component). Perhaps the component is
only one or two bits (e.g., introduced through changing luminance
characteristics of the document at predetermined areas, or relative
to other digital watermark components). But the bit change
indicates an inspection and successful validation. The document is
subsequently modified each time it is inspected and deemed valid.
(A validity determination is made based on a successful calculation
and verification of the PUF. For example, the PUF is checked
against a "watch list" of suspected identifiers, or can be compared
to a machine-readable version of the same.). Instead of modifying
the document through printing, other techniques like exposure to
predetermined light or radiation may be used. In these later cases,
the document includes, e.g., photosensitive materials that change
with exposure to the light or radiation.
[0283] Some possible combinations of this disclosure include the
following. Of course, other combinations will be evident to those
of ordinary skill in the art. We reserve the right to present these
and other combinations as claims in this or continuing
applications.
[0284] F1. A method of monitoring for counterfeited documents
comprising:
[0285] optically scanning a plurality of documents;
[0286] identifying a physically random function associated with
each of the plurality of documents;
[0287] determining if the physically random function associated
with each of the plurality of documents are statistically similar;
and
[0288] signaling such a similarity when it arises.
[0289] F2. The method of F1 wherein the physically random function
is determined from fibers found in the documents.
[0290] F3. A method comprising:
[0291] determining a physically random function (PRF) associated
with a document;
[0292] representing the PRF as a plural-bit identifier; and
[0293] steganographically embedding the plural-bit identifier in
artwork or graphics carried by the document.
[0294] F4. The method of F3 wherein the graphics comprise at least
a photograph of an authorized bearer of the document.
Advances in First-Line Defenses
[0295] Historically, "first-line" inspection has referred to
inspection techniques that are carried out through visual
inspection and/or touch. First-line inspection has been a
cornerstone of security printing since its inception.
[0296] Technology proliferation has forced reevaluation of
first-line inspection techniques, both from a threat and benefit
side. Counterfeiting technology has advanced to a point where any
first-line techniques are now easily counterfeited. At the same
time high-quality imagers with significant resolution (300 DPI+)
are being widely distributed (e.g., on cell phone cameras).
[0297] A series of first-line "+" approaches are needed. We outline
a few "+" approaches below. Some of these approaches modify
existing features that are inspected with aid of widely available
consumer devices. Other approaches introduce new features and
functionality. Examples of available consumer devices include,
e.g., cell phones, PDAs (e.g., think Pocket PCs) and portable music
players, each that include an optical imager (or camera) and a
display. These devices are augmented to include software to
facilitate the functionality noted below. Instead of software,
hardware implementations are acceptable as well. (Artisans of
ordinary skill will be able to make and use such software without
undue experimentation given this disclosure relative to what is
already known in the art.)
[0298] In a first implementation a document includes
extraordinarily small micro-print that is imperceptible to the
naked human eye. A user (e.g., at a point of sale location)
optically scans a document with her camera-equipped cell phone.
Software executing on the cell phone analyzes the optical scan
data, finds and then magnifies the micro-printing, and presents the
magnified micro-printing via a device display. The software may
include a character recognition module that allows recognition of
the micro-printing. If an error is found in the micro-printing (or
if an expected error is not found) the device preferably prompts
the user of such. Preferably, only those document regions including
such micro-printing are provided via display for user inspection.
(In some cases the ASCII values of micro-printing are hashed and
compared against a predetermined or expected value. The user is
notified if the calculated and expected values differ
significantly.).
[0299] In some variations of this first implementation, the
micro-printing is provided on the document surface in proximity to
a fiducial or hash mark. The fiducial provides a recognizable
feature for the character recognition software. The fiducial's
presence signals an expected presence of micro-printing. Once a
region is identified as including the fiducial, a predetermined
area around the fiducial is searched for expected micro-printing.
The micro-printing is presented to a user via a device display.
[0300] In a second implementation, a document includes materials
that fluoresce in the near-IR spectrum (e.g., many available inks
have near-IR responses). While this fluorescence is beyond human
perceptibly, many of today's devices (e.g., camera-equipped cell
phones) are sensitive to this portion of the spectrum. The camera
picks up features conveyed in the near-IR, which are presented to
the user via the display. The use of near-IR in the art of security
printing is well known. One variation of this second implementation
includes a camera that picks up fluoresce or reflection from
"hidden" features. These hidden features may be visible solely in
the near-IR or may require an additional filter with a specific
spectral response to highlight the feature. Another variation of
this implementation involves illuminating a document with a light
or strobe (a feature that is becoming common on cell phones &
PDA's) that enable the feature to become visible.
[0301] A third implementation harkens back to our above discussion
of PRF's. Consider a document that includes security fibers or
other visually perceptible features. A spatial mapping of the
features is determined (see FIG. 16). The mapping is represented by
an identifier or other characteristics. The identifier or
characteristics are provided as a machine-readable component (e.g.,
as a digital watermark component or payload).
[0302] The digital watermark may also include a so-called
orientation component, which is helpful in resolving image
distortion such as rotation, scaling and translation. See, e.g.,
assignee's U.S. Pat. Nos. 6,704,869, 6,408,082, 6,122,403 and
5,862,260, which are each hereby incorporated by reference. In some
cases a spatial mapping of the features is conveyed as a watermark
orientation component, much like a mapping of fingerprint minutia
discussed in assignee's U.S. Published Patent Application No. US
2005-0063562 A1, published Mar. 24, 2005, which is hereby
incorporated by reference.
[0303] A user scans a document with her camera (e.g., cell phone or
PDA). A watermark reader reads a watermark from the scan data to
obtain the embedded identifier or characteristics. Cooperating
software reconstructs an expected, relative spatial placement of
the security fibers based on the embedded identifier or
characteristics. The expected spatial placement is provided to the
user via the device display. The presentation may include, e.g., a
graphical representation of an expected placement of security
fibers relative to the document (see FIG. 17). The representation
can include dots, lines, marks, etc. In some implementations, an
image of the document is shown in the display (as captured by the
device) and a graphical overlay is provided over the document to
show the expected placement of the security fibers. A user can
visually check the document to determine accurate placement.
[0304] Another variation automatically determines an actual
placement of PRF indicators (e.g., security fibers) and presents
via a device display the actual placement vs. the expected
placement. The actual placement of PRF indicators is found through,
e.g., analysis of optical scan data.
[0305] Instead of placement of security fibers, a watermark may
reveal an expected location, shape or details of other document
features such as designs, seals, etc.
[0306] A watermark payload may be secured through cryptographic
means to provide additional security. A public key is provided to a
user's device to decode a watermark payload. The public key can be
used to validate a digital signature issued by a document issuing
authority for the document being inspected. The hash used to create
the digital signature would be based on a PRF or PUF. The digital
signature would be created and embedded into a machine readable
feature during printing.
[0307] A fourth implementation relies on so-called high-resolution
watermarks (fragile, robust, tamper-evident, etc.). These
watermarks may only be detectable through high resolution scanning
Resolutions of 10K DPI are common in security printing, this allows
for machine readable features of the same resolution. By operating
at this resolution, successful attacks would be required to operate
at a similar resolution if not 2.times. (Nyquist). This places the
features well outside the range of current imaging workflows
(typically 1200-4800 DPI) and hence outside of all but the most
specialized of equipment usually reserved for security printers
(e.g., Simultan Printing Presses, Jura RIPs, etc.). This frequency
is also in a similar band to where naturally occurring PRF's
typically appear (ink bleed, dot gain, voids, etc.).
[0308] A fifth implementation relies on audible feedback. A tone is
generated by a device (e.g., cell phone, PDA, etc.) as an imager
sweeps across a document. The tone is triggered, e.g., when a
watermark is detected and/or when the watermark's payload matches
or otherwise corresponds to the predetermined PRF characteristics.
In some variations of this fifth implementation, an audible scale
(e.g., think ring-tone) is influenced by the speed of the optical
swipe. The ring tone will only sound or will vary in sound
depending on the speed of the optical sweep (a simple gyroscope
with speed measurement in the device can help facilitate this
functionality). Of course, speed of optical sweep and watermark/PRF
detection can be combined to generate a predetermined sound.
[0309] An important criteria in many of the above implementations
is to leave the decision process of whether a document is authentic
to a human observer, and not to a device. For example, if
authentication relies solely on a device flashing a green light,
signaling that a document is authentic, counterfeiting attacks will
target the device. Such attacks might render device-determined
authentication indications suspect.
[0310] Some possible combinations of this disclosure include the
following. Of course, other combinations will be evident to those
of ordinary skill in the art. We reserve the right to present these
combinations as claims in this or continuing applications.
[0311] G1. A method of authenticating a security or identification
document with a handheld computing device, the device comprising an
optical sensor and a display, the document comprising
micro-printing provided thereon, wherein the micro-printing is
generally imperceptible by an unassisted human observer, said
method comprising:
[0312] receiving from the optical sensor optical scan data
corresponding to the document;
[0313] analyzing the optical scan data to recognize the
micro-printing;
[0314] scaling or magnifying the micro-printing;
[0315] providing at least some of the scaled or magnified
micro-printing via the display.
[0316] G2. The method of G1 wherein the document further comprises
a micro-printed fiducial.
[0317] G3. The method of G2 wherein the micro-printing is
recognized at least in part through identification of the
fidicual.
[0318] G4. A handheld computing device comprising:
[0319] a display;
[0320] an optical sensor;
[0321] processing circuitry; and
[0322] electronic memory, wherein said memory comprises executable
instructions stored therein for execution by the processing
circuitry, said instructions comprising instructions to carry out
the method of any one of F1-F3.
[0323] G5. A method of authenticating a security or identification
document with a handheld computing device, the device comprising an
optical sensor, and at least a speaker, the document comprising
machine observable features provided thereon, said method
comprising:
[0324] receiving from the optical sensor optical scan data
corresponding to the document;
[0325] analyzing the optical scan data to observe the features;
[0326] based at least on observed features, providing an audible
signal via the speaker.
[0327] G6. The method of claim G5 wherein the audible signal is
dependent on a speed at which the optical sensor is moved for
scanning relative to the document.
[0328] G7. The method of claim G5 wherein the machine observable
features comprise digital watermarking.
[0329] G8. The method of claim G7 wherein the machine observable
features are randomly placed.
Concluding Remarks
[0330] 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. To provide a comprehensive disclosure without
unduly lengthening the specification, applicants hereby incorporate
by reference each of the patent documents referenced above.
[0331] The methods, processes, and systems described above may be
implemented in hardware, software or a combination of hardware and
software. The methods and processes described above may be
implemented in programs executed from a system's memory (a computer
readable medium, such as an electronic, optical or magnetic storage
device).
[0332] We have used Blue (B) ink and Metallic Blue (MB) ink in some
sections of the above discussion for consistency and to ease the
description. Use of these inks are for illustration only should in
no way limit the disclosure. Indeed, we contemplate many different
ink colors and finishes. We also contemplate use of more than two
types of ink, and more than two printing plates. Also, reference to
Pantone is for illustrative purposes also. There are many other
suitable ink manufacturers.
[0333] Of course, photocopying (color copying) a security document
including our metameric inks would be very difficult. First, the
copy would need to include metallic ink capabilities. Further, even
if a copying process included metallic ink, the metallic ink would
need to be arranged so that it was not readily distinguishable
(e.g., visually distinguishable) from the non-metallic ink and
would need to be arranged in a diffraction pattern to yield an
expected signature.
[0334] 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 patents/applications are also
contemplated.
* * * * *