Title of Invention

A METHOD OF DETERMINING WHETHER AN ANALOG FORM OF AN OBJECT IS AN ORIGINAL ANALOG FORM

Abstract Techniques for determining authenticity of analog forms such as packaging or documents (117). One of the techniques determines whether the analog form has been made directly from a digital representation (903) or by photocopying or scanning an analog form. The technique makes the determination by comparing (911) an original digital representation of a portion of the analog form with a digital recording (203) of the portion from the analog form and measuring differences in features that are affected by the operations of photocopying or scanning. The original digital representation (105) and the analog form may have a "noisy", i.e. random or pseudo random pattern. Such noisy patterns may further be used for other authentication purposes, such as determining whether the portion of the analog form that has the noisy pattern has been altered and to carry hidden messages. The noisy pattern may carry a logo or may be, part or all of a barcode.
Full Text A METHOD OF DETERMINING WHETHER AN ANALOG FORM OF AN OBJECT IS
AN ORIGINAL ANALOG FORM
Cross references to related applications
The present application claims priority from U.S. Provisional Application 60/380,189,
Method and Apparatus for Copy Protection with Copy-Detectable Patterns, having the same
inventors as the present application and filed 5/14/02 and further claims priority from and is
a continuation-in-part of USSN 10/287,206, J. Zhao, et al., Apparatus and methods for
improving detection of watermarks in content that has undergone a lossy transformation,
filed 11/4/2002. The sections Watermarks that are embedded using message-based keys and
Using watermarks to locate alterations in digital documents and analog documents made
from digital documents from that application are included in their entirety in the present
application. All of USSN 20/287,206 is further incorporated by reference herein for all
purposes.
Background of the invention
1. Field of the invention
The invention relates generally to security features in printed documents and more
specifically to visible authentication patterns in printed documents. The visible
authentication patterns can be used to distinguish original printed documents from
photocopies of those printed documents, to detect alterations in documents, and to carry
hidden and/or visible messages.
2. Description of related art
A prerequisite for a commercial society is being able to distinguish authentic items from
false or counterfeit items. With documents, the questions that may need to be answered to
determine a document's authenticity include the following:
• Is the document an original or a copy of an original?
• Has the document been altered since it was first made?
• Is the document authorized?
Many techniques have been developed to make it reasonably possible to answer these
questions from the document itself. Techniques which make it easier to determine whether a
document is an original or a copy include the complex etchings used in paper money, the

photographs used in ID cards, and special papers. Special papers and inks have been used to
detect alterations. Techniques for showing that a document is authorized have included
signatures and seals.
With the advent of digital scanning and printing techniques, digital watermarks have been
used to authenticate printed documents. A digital watermark is a message that is embedded
in a digital representation of a document by adding noise that carries the message to a
graphic element in the document. When used for authentication purposes, the message is
generally invisible and can be read only if the location of the information making up the
message in the graphic element is known. For a survey of digital watermarking techniques,
see Appendix A, beginning at col. 17, line 27 of United States Patent 6,345,104, Rhoads,
Digital watermarks and methods for security documents, issued 2/5/02, which is
incorporated herein by reference for all purposes. For an example of how digital watermarks
may be used for authentication purposes, see United States Patent 6,243,480, Jian Zhao,
Digital authentication with analog documents, issued 6/5/01.
Progress in the technology of copying has diminished the value of all of the techniques that
permit one to determine from the appearance of a document whether it is authentic. Because
of this progress, counterfeiting not only of money and financial instruments, but also of other
documents such as ID cards and diplomas as well as of packaging and labels causes huge
losses, ranging to 5% to 8% of worldwide sales of branded products, and endangers the
reputation and value of the brands themselves. Moreover, the growth of the Internet drives
the business of counterfeited documents (fake IDs, university diplomas, checks, and so on),
which can be bought easily and anonymously from hundreds of companies on the Web. As
the precision of scanners, digital imaging software and printers increase, the problem will
only get worse.
What is needed as the scanners, digital imaging software, and printers get better is new ways
of adding information to a document to make it possible to determine whether it is an
original or a copy, whether it has been altered, and/or whether it has been authorized. Efforts
in this area have included the following:
Embedding multiple watermarks in a document
U.S. patent 6,332,031, Rhoads, et al., Multiple watermarking techniques for documents and
other data, issued Dec. 18, 2001, discloses embedding several watermarks in the document,

each of them with different properties or in different domains. If the document is
photocopied or scanned and printed in order to produce a counterfeit, the embedded
watermarks will be altered or damaged. The properties of the watermark or the domain in
which it is embedded will affect the degree to which it is altered by the copying process.
Thus, the relative degree of alteration of each watermark can indicate whether the document
is an original or copy. The use of watermarks in this fashion has a number of advantages:
• It is flexible: a digital watermark can in theory be inserted into any document, because it
merely introduces unnoticeable modifications to the document.
• Because it is invisible, it can be used to determine the source of the counterfeits.
• The possible presence of watermarks forces the counterfeiter to reproduce the whole
document with very high fidelity.
The advantages of watermarks are also their disadvantages. Because digital watermarks
used for security purposes are made by adding invisible noise to a document, they often
cannot be read where the document that contains them has been subject to wear and tear.
Because they are hidden in the noise in a document, it is difficult to hide the watermarks in
documents such as banknotes where every element of the design is fixed and there is thus no
room for noise.
Embedding information that cannot be reproduced by a photocopier
A document may contain a part which is invisible in the visible light range because it is
printed with an ink that is visible in ultra-violet light. The photocopier, which operates using
visible light, cannot reproduce it. See US patent 5,868,432, Mantegazza, Documents with
anticopying means to prevent reproducibility by photocopying, issued 2/9/99.
The information may still require more resolution than the scanning-printing process is
capable of. See U.S. patent 5,708,717, Alosia, Digital anti-counterfeiting software method
and apparatus, issued 11/13/98, which discloses a method for combining a source image and
a latent image which is visible only when viewed through a special decoder lens. This latent
image can, for example contain the words "authentic" repeated several time, or more
document-specific information such as the personal information in the portrait of a ID card.
However, since the latent image is printed with "sub-pixel" precision, it cannot be easily
reproduced. Of course, what is "sub-pixel" today may be easily reproducible tomorrow.
Holograms are inserted on documents such as ID cards and banknotes because they are
assumed to be easy to detect by the human eye and hard to reproduce with high fidelity.

However, while anyone can see whether a hologram is present on a document, an untrained
observer will generally be unable to detect whether the hologram is authentic or a copy.
Common problems of invisible copy protection features
A problem that all of the invisible copy protection features have is that their invisibility
makes them completely useless to people who do not have the special instruments needed to
read them. Moreover, the invisibility of the features causes problems with printing and/or
detection. With the watermarks, the need to keep the watermarks invisible necessarily
makes them hard to detect, and that is particularly the case when wear and tear add extra
noise to a document. With invisible ink, both printing and detection are complicated, and
that is also the case with latent images printed with "sub-pixel precision".
What is needed is techniques that can reliably determine, at a lower cost, whether a
document is an original or a copy, whether the document has been altered, or whether it is
authorized, that make it possible for the public to see that a document may be easily
authenticated, and that can be easily integrated with other techniques for authenticating a
document. It is an object of the inventions disclosed herein to provide such techniques.
Summary of the invention
The object of the invention is attained in one aspect by techniques for determining whether
an analog form of an object is an original analog form, that is, an analog form made from an
original digital representation instead of by photocopying or scanning an analog form, In a
method employing the techniques, a portion of a digital recording made from the analog
form is compared with an original digital representation of the portion of the analog form to
determine a degree of dissimilarity between the recorded portion and the original digital
representation of the portion and using the degree of dissimilarity to determine whether the
analog form is an original analog form. A further characteristic of the invention is that the
dissimilarity that is determined is a dissimilarity that is caused by operations involved in
making a non-original analog form.
Other characteristics of this aspect are practicing the method in a node in a network which
receives the digital recording from another node in the network and returning an indication to
another node whether the analog form has been determined to be an original analog form, as
well as practicing the method in a processor to which a digital recording device and an

output device are attached. The processor makes the digital recording from input received
from the digital recording device and provides an indication whether the analog form has
been determined to be an original analog form to the output device.
In an advantageous embodiment of the invention, the original digital representation of the
portion has a noisy pattern. The original digital representation may be made using a key and
the original digital representation may have a function in the analog form in addition to
permitting determination of whether the analog form is original. The function may be to
serve as a barcode or a background image or to carry a message.
Another aspect of the invention is a method of performing an authenticity check on an
analog form. The method compares a digital recording of a noisy pattern in the analog form
with an original digital representation of the noisy pattern and the result of the comparison is
used to perform the authenticity check. The technique may be used to determine whether a
portion of the noisy pattern has been destroyed in the analog form. The noisy pattern may
further contain a message.
Still another aspect of the invention is a method of hiding a message in an analog form In
the method, a digital representation of a visible noisy pattern in which the message has been
hidden is made and is included in the analog form.
Other objects and advantages will be apparent to those skilled in the arts to which the
invention pertains upon perusal of the following Detailed Description and drawing, wherein:
Brief Description of the Accompanying Drawings
FIG. 1 is an overview of how a visible authentication pattern (VAP) is generated and
inserted into a document;
FIG. 2 how a VAP is recorded from a document;
FIG. 3 is a flowchart showing in overview how a VAP can be used in authentication;
FIG. 4 is an overview of printing and authentication of original and non-original analog
forms;
FIG. 5 shows GUIs for watermark detection and alteration detection;
FIG. 6 is a graph showing correlation between energies in bands of frequencies in an
original digital representation of a VAP and a VAP recorded from a non-original
document;

FIG. 7 is a graph showing correlation between energies in bands of frequencies in an
original digital representation of a VAP and VAPs recorded from original
documents;
Fig. 8 shows how a message-based key can be used to embed a contentless watermark in an
image;
FIG. 9 shows a technique for determining whether a particular digital representation is
derived from a digital representation which was watermarked using a message-
based key;
FIG. 10 shows how a VAP may be used to detect alteration of a document; and
FIG. 11 shows how a VAP may be incorporated into a bar code or into a logo.
Reference numbers in the drawing have three or more digits: the two right-hand digits are
reference numbers in the drawing indicated by the remaining digits. Thus, an item with the
reference number 203 first appears as item 203 in FIG. 2.
Detailed Description
Using the mere presence of watermarks to authenticate a document
Generally speaking, authentication techniques for documents which involve watermarks use
the watermark to hide some kind of authentication information for the document in a
graphical element in the document. An example is using the watermark to hide a digest
made from the document's character codes, as explained in U.S. patent 6,243,480, cited
above. A difficulty with techniques that use watermarks to hide authentication information
in a graphical element of a document is that wear and tear on the document often renders the
watermark unreadable.
USSN 10/287,206, the parent of the present application, explores ways of obtaining at least
some information from unreadable watermarks and ways of making watermarks more robust
in the face of lossy transformations such as those caused by wear and tear on a document.
Among the things that the inventors of USSN 10/287,206 realized in the course of their work
were first, that a watermark's mere presence could be used to authenticate a document, and
second, that the mere presence of a watermark could be used to discover where a document
had been altered. The portions of USSN 10/287,206 that deal with these realizations follow.

Watermarks that are embedded using message-based keys: FIGs. 8 and 9
The standard application of digital watermarks is to hide a message in a digital
representation. One of the uses of such a message is validating or authenticating the digital
representation: the digital representation being validated is believed to contain a watermark
which contains a particular message; the watermark is read and its contents are compared
with the particular message. If they agree, the digital representation is valid or authentic.
When the digital representation has undergone a lossy transformation, the watermark may
become unreadable; the techniques discussed in USSN 10/287,206 permit limited validation
or authentication in such situations. A general problem with validation by means of
messages contained in watermarks is that validation often involves long messages such as
social security numbers or account numbers, while watermarks containing such long
messages are less robust than watermarks containing short messages, and are therefore more
likely to be rendered unreadable by lossy transformations.
A solution to this general problem is based on the observation that for validation or
authentication purposes, there is no need that the watermark actually contain the message
that forms the basis for the validation or authentication; all that is required is that a given
watermark will be present in a digital representation only if the watermark was made using
the message that forms the basis for the validation. In that case, there is no need for the
watermark to be readable; instead, the mere presence of the watermark permits the digital
representation to be validated. Moreover, because it is the watermark's presence and not its
content that shows that the digital representation is valid or authentic, the watermark's
content need do nothing more than indicate the watermark's presence and need be no longer
than is required to do that; indeed, the watermark vector for a such a watermark need only
specify the value of a single bit. This in turn makes such watermarks far more robust than
watermarks that contain the message that forms the basis for the validation or authentication.
One way of making a watermark whose mere presence in a digital representation validates or
authenticates the digital representation is to use the message to determine the location of the
watermark in the digital representation. This is shown at 801 in FIG. 8. A key function 805
(f) is used to make a key 806(K2) from a message 803 (m): K2=f(m); where required, the
function 805 may use a secret key K1_as well as m to make the key: K2=f(K1,m). Key 806
is then provided to watermark embedder 809 along with a short (minimum 1 bit) watermark
vector WM 807 and watermark embedder 809 embeds a watermark made using watermark
vector 807 at the locations in watermarked digital representation 813 indicated by key 806.

The watermark is shown in FIG. 8 by the dotted boxes labeled 807 in digital representation
813. Since message 803 is now no longer contained in the watermark, but instead used to
make key 806 and short watermark vector 807 need only be 1 bit in length, the length of the
message has no effect whatever on the robustness of the watermark. As is well known in
mathematics, there are many functions which can be used to generate key 806 from message
803 in a fashion such that key 806, and thus the watermark made with it, is unique to the
message. The degree of uniqueness required may of course vary with the application. In
some cases, the function may be an identity function, i.e., the key is the message itself. An
advantage of the technique is that the function determines the length of the watermark key,
and thus, the key can be made as long as is required for a particular application.
FIG. 9 shows at 901 a system that determines whether a digital representation 903 that is
believed to contain a watermark made in the manner just described is authentic. Digital
representation 903 contains a set of locations 905 that should contain watermark vector 807
if digital representation 903 is in fact derived from digital representation 813. The locations
are at positions which in digital representation 813 were determined by key 806. The system
that is doing the authentication obtains message 803 and also obtains or is in possession of
key function 805. Key function 805 is applied to message 803 to produce key 806 as
described above. The system then provides key 806 to watermark reader 907, which uses it
to find locations 905. When a location is found, it is output to comparator 909, as shown at
909. Short watermark vector 807 is also in possession of system 901, and it is provided to
comparator 911 to compare with the value of each of the locations 905 in turn. The result
912 of each comparison goes to aggregator 913, where the results are aggregated to produce
overall result 915, which indicates whether the watermark that was embedded in digital
representation 813 is present in digital representation 903. Comparator 911 and aggregator
913 can use any of the techniques previously discussed with regard to unreadable
watermarks for doing the comparison and the aggregation. As described below for the
techniques used with unreadable watermarks, the pattern of locations 905 that match the
watermark in digital representation 813 may be used to show locations at which digital
representation 903 has been altered.
In some applications, aggregator 913 will produce a visual result of the comparison. An
example of such a comparison is shown at 501 in FIG. 5. There, the blocks to which the
watermark was applied have different shades depending on the extent to which the presence
of the watermark was detected. The lighter the block is, the stronger the presence of the
watermark in the block. Because image 501 has undergone lossy transformations, the

distribution of blocks with strong watermarks will not be the same as in the original, but the
errors caused by the lossy transformations are random, and consequently, if the image is
authentic, all areas which contain the watermark should have roughly the same distribution
of light blocks as shown at 501, This visualization technique can of course be used as well
with watermarks in which the message determines the watermark's contents.
Using watermarks to locate alterations in digital documents and analog documents
made from digital documents
One way of attacking a digital document or an analog form made from the digital document
is locally modifying an image in the document or form to change its semantic content.
Examples of local modifications can be:
• modifying the plate number on the image of a car captured by a DVR on the scene of an
accident/crime; or
• modifying areas of the portrait on an ID card; or
• replacing the portrait on an ID document.
If the document or form is watermarked, the counterfeiter's goal is to change the semantic
content of the digital document or form without rendering the watermark incorrect or
unreadable. In general, when a watermark is robust enough to be readable, it will not be
difficult for the counterfeiter to make small changes in the document or form without
rendering the watermark incorrect or unreadable. On the other hand, the very robustness of
the watermark makes it useful for detecting and tracking alterations.
In order to use a watermark to locate an alteration, one need only know the locations at
which the watermark is expected to be and its watermark vector. Since the technique does
not require that the watermark have any particular content, the watermark vector need only
be a single bit. Once the detector knows the watermark locations and the watermark vector,
the detector can use the watermark vector w' which is a replica of the original watermark's
watermark vector w and compare w' with the watermark w" in the questionable content.
Differences between w' and w" may show whether the digital document or analog form that
is the source of the questionable content has been modified and if so, which portions were
modified.
In more detail, the detector compares the watermark vector w" in each subpart (termed
herein a block) of the digital document or analog form with vector w'. The comparison
indicates whether each block of the document or form holds the correct watermark

infonnation. In a digital document, if there has been no alteration, most blocks will contain
the correct watermark information. With analog forms, the print-and-scan process
deteriorates the watermark, and consequently, not all blocks will hold the correct watermark
information (e.g. there can be in the order of 20% to 40% errors). These printing and
scanning errors are generally of random nature and therefore can be expected to be
distributed more or less uniformly on the analog form. Thus, if the image has been locally
altered and has thereby lost its watermark in the altered areas, the watermark detector will
respond to the altered areas in the same way that it responds to areas that are not
watermarked. In doing so, the watermark detector detects the alteration. The technique can
also be used to show the strength of the watermark in each area of the image.
The replica watermark vector used to detect alterations or watermark strength may come
from any source. Examples include the original image, a watermark vector from the
questionable content that has been successfully read, or a watermark vector which has been
generated anew from the message. Adaptive embedding and detection may be used to
increase the effectiveness of detecting alterations. For example, areas of the content that
need special protection against change may receive watermarking of a greater strength than
other areas of the content, and the greater strength of the watermarking in these areas may be
taken into account when the watermarks are analyzed as described above. Of course, the
technique as used to show the strength of the watermark in each area of the image may be
employed to aid in the design of masks for adaptive embedding and detection.
Different techniques inspired by statistics, signal processing or pattern recognition can be
applied to automatically detect areas that contain an abnormally large number of blocks that
hold incorrect information (or no information at all). For example, one technique inspired
from pattern recognition is to determining connections of incorrect blocks, and extract those
connections that are higher than a threshold. Another technique would be to determine in all
areas of size NxN of the analog form whether there are more than P incorrect blocks. Yet
another technique from signal processing is to assign positive values to correct blocks and
negative values to incorrect blocks and then low-pass filter the resulting matrix. The areas of
the filtered matrix in which values are under a threshold are detected as having been altered.
Finally, statistics can be applied in all approaches to characterize areas of the images that are
not altered and those that are altered, and to determine detection parameters relatively to the
user's expectation (e.g. minimum size of altered areas, probability of false alarm/rejection,
etc). It is also possible to display to the user an image with the incorrect and correct blocks in
different colors, to allow human interpretation of the data.

FIG. 5 shows the effect of alterations on watermark strength and also provides an example
of a graphical way of showing altered areas. Here, image 501 was modified after it was
watermarked by replacing the face in with another face which was not watermarked in the
way that the face in image 501 was watermarked. The result of the modification is image
502. When image 502 is compared with image 501, it will be seen that the facial area of
image 502 is darker than the facial area of image 501. This in turn shows that the blocks in
the facial area of image 502 are far more weakly watermarked than the blocks in the facial
area of image 501. The weak watermark in the facial area of image 502 is of course a direct
consequence of the modification. When a filter is applied that highlights areas with many
weak blocks, the result is image 503, in which modified area 505 clearly stands out.
Extensions of the technique
■ Detecting more than one altered area
■ Using external modules (e.g. face recognition), to focus detection of alteration on the
most semantically significant areas (e.g. the eyes in an ID photo)
■ Multiple scanning of physical document to cancel out scanning variability.
If the watermark is unreadable, the alteration detection may be used for analyzing the
reasons for its unreadability.
Visible authentication patterns
The foregoing realizations were followed by the realization that led to the present invention:
when a watermark's mere presence is being used to determine authenticity of an analog form,
the watermark is being used as a contentless pattern. Since the pattern has no content, there
is no longer any need for it to be invisible; instead, it can be added to the document as a
visible element. In the following, visible patterns that are used for authentication are termed
visible authentication patterns or VAPs. Because the VAP is visible, it is far easier to detect
than is a watermark. It is, however, still able to perform all of the authentication functions of
invisible watermarks and in addition lets consumers of the document know that the
document's authenticity is protected.
Terminology

The following terminology will be used in the Detailed Description to clarify the
relationships between digital representations and analog forms.
A digital representation of an object is a form of the object in which the object can be stored
in and manipulated by a digital processing system. Objects may be or include as
components documents, images, audio, video, or any other medium of which a digital
representation can be made.
an analog form of a digital representation is the form of an object or component that results
when the digital representation is output to an analog device such as a display, printer, or
loudspeaker.
a digital recording of an analog form is a digital representation made from the analog form.
The manner in which the digital recording is made depends upon the medium; for example,
for a documents or an image, digital recording is done by digitizing an image made from an
analog form of the document or image.
an original digital representation is a digital representation made or copied by someone
authorized to do so; an original analog form is one made from an original digital
representation.
a non-original digital representation is one that is made by digitally recording an analog
form without authorization; a non-original analog form is made from a non-original digital
representation or by photocopying an analog form.
a document will be given the special meaning of any analog form which is produced by a
printing process, including documents in the more usual sense of the word, labels,
packaging, and objects that are themselves imprinted. To the extent that reasonable
analogies can be made, everything in the following that is said about documents may be
applied also to other media. For example, an audio analog form may include an audible
authentication pattern that is the audio equivalent of the VAP.
Making a visible authentication pattern: FIG. 1
The paradox of the visible authentication pattern is that while the pattern is visible, a
possible counterfeiter must not be able to modify the pattern so that it will authenticate a

document that is not authentic. This end is achieved in a preferred embodiment by making
the pattern noisy, i.e., a large part of the value of the pixels making up the pattern is
apparently randomly determined. Because the pattern is noisy, it is impossible to tell what
values the pixels making up the digital representation of the pattern should have without
access to the original digital representation of the pattern. On the other hand, given the
original digital representation of a VAP, one can compare a digital recording of a VAP from
a document with the VAP's original digital representation, determine how the recorded VAP
has been altered with regard to the VAP's original digital representation, and can determine
from the differences how the document in question has been altered. As will be seen in more
detail in the following, alterations that can be detected include those involved in making non-
original documents and those involved in altering information in a document.
FIG. 1 shows one way of making a visible authentication pattern and inserting it into a
document. There are three steps:
• generating a digital representation of the pattern, shown at 101;
• an optional step of adding a visible logo or legend to the authentication pattern, shown at
107; and
• inserting the authentication pattern into the document, shown at 113.
The original digital representation of the pattern 105 can be generated in any way which
produces a result in which the pattern's pixels appear to have values with a strong random
component. The digital representation of pattern 105 may be a gray-scale pattern, or it may
employ colored pixels. It is particularly useful to employ a key to generate the pattern; the
key 103 is used as a seed for a pseudo-random number generator which produces the
sequence of values which are given to the pixels in the pattern. Uses of the key will be
explained in detail later. The original digital representation of pattern 105 may also include
components which aid in locating the pattern in a digital representation made by scanning a
document that contains pattern 105. In pattern 105, black border 106 performs this function.
A visible logo or legend 109 can be added to the original digital representation of pattern 105
to make the original digital representation of pattern 111 without compromising pattern 105's
noisiness because only a part of the value of the pixels making up the pattern need be
randomly determined. Thus, the logo or legend can be superimposed on pattern 105 by
manipulating the values of the pixels making the logo or legend in a way that preserves their
randomness while causing the logo or legend to appear. For example, if pattern 105 is a gray
scale pattern, the legend or logo can be made by making the pixels of the legend or logo

uniformly darker or lighter relative to their original random values. The technique is similar
to adding a visible watermark to an image, except that it preserves the noisiness of pattern
105.
Once the original digital representation of pattern 111 has been made, it is inserted into the
original digital representation of the document 115, as shown at 113. When document 117 is
printed from original digital representation 115, document 117 includes printed visible
authentication pattern 119. Of course, the document may be printed onto a substrate that
already has printed material on it. Thus, pattern 119 may be added to a preprinted substrate.
Using a visible authentication pattern to authenticate a document: FIGs. 2 and 3
When a document that contains a printed VAP 119 is authenticated, the following happens:
• a printed VAP 119 is detected in the document.
• a digital recording of the detected printed VAP 119 is made.
• the digital recording of the printed VAP is compared with the original digital
representation of the VAP; and
• authenticity is determined on the basis of the comparison.
The manner in which the digital recording of the printed VAP is compared with the original
digital representation of the VAP depends on the kind of authentication being done; further,
the authentication of a given document may involve several different kinds of comparisons
being made between the digital recording and the original digital representation. For
example, a digital recording of a visible authentication pattern on the amount field of a check
may first be compared with the original digital representation to determine whether the check
is a counterfeit and second to determine whether the amount in the amount field has been
altered.
FIG. 2 shows detecting the printed VAP and making a digital recording of the VAP in a
preferred embodiment. Both are done using the "Scanread" application program available
from MediaSec Technologies. Other applications that detect a portion of a document and
make a digital recording of it may also be employed. Scanread 201 uses black border 106 to
detect the presence of visible authentication pattern 119 in printed document 117 and then
makes digital recording 203 of visible authentication pattern 119. FIG. 3 shows a general
flowchart 301 of a program that uses digital recording 203 and original digital representation
111 of VAP 119 to determine authenticity. Original digital representation 111 of the VAP

may be the original itself, a copy of the original, or a new original digital representation 111
made in exactly the same way as the first original digital representation. Original digital
representations obtained by any of these methods aTe of course exactly equivalent, and which
method is used is a matter of implementation issues such as the cost of storage for the
original digital representation of the VAP, the cost of transmitting the original digital
representation of the VAP across a network, and the cost of generating the original digital
representation each time it is required.
Beginning at 303, features of digital recording 203 and original digital representation 111 are
compared at 305; what features are compared and how they are compared depends on the
kind of authentication being done. If the differences between digital recording 203 and
original digital representation 111 exceed a threshold (307), there is an authentication
problem and branch 309 is taken. The threshold will also depend on the kind of
authentication being done. In branch 309, the existence of a problem is indicated to the
application program that is doing the authentication at 311. Where it is useful, the program
may also provide information about the comparison (315); again, the kind of information and
the manner in which it is provided will depend on the kind of authentication. For example, if
the amount in the amount field appears to have been altered, the program may display an
image that shows which of the pixels of the original digital representation appear to have
been altered in the digital recording of the visible authentication pattern. If the differences
do not exceed the threshold, branch 317 is taken. There, the fact that no authentication
problem has been detected is indicated to the application program that is doing the
authentication. Both branches and the program terminate at 321.
Using visible authentication patterns to distinguish an original document from a non-
original document: Figs. 4, 5,
One way a visible authentication pattern can be used to authenticate a document is by
determining whether a document is an original, i.e., was printed from an original digital
representation or is a non-original, i.e., was photocopied from document or was printed from
a non-original digital representation, that is, a digital representation that was made from an
unauthorized digital recording of a document. The reason a visible authentication pattern
can be used in this way is that printing a document from its digital representation and making
a digital representation of a document from a digital recording of it or photocopying a
document always result in losses of information in the visible authentication pattern,
regardless of how precise the printing, digital recording, or photocopying processes are;

consequently, one can determine by comparing an original digital representation of a visible
authentication pattern with a digital representation made by recording the visible
authentication pattern from a document whether the document is an original or a non-
original. In the case of an original document, the visible authentication pattern will have
been printed once and digitally recorded once; in the case of a non-original document, the
visible authentication pattern will have been printed and digitally recorded once to produce
the original document from which the non-original document was made, and then, depending
on how the non-original document was made, either photocopied or again printed and
digitally recorded, resulting in a greater loss of information in the non-original document's
visible authentication pattern than in the original document's visible authentication pattern.
The basic technique is shown in detail in FIG. 4. At 401 is shown how authentication using
a visible authentication pattern works with an original document. Original digital
representation 403 of the document contains an original visible authentication pattern (ovap)
405. Original digital representation 403 is then printed at 407 to produce original analog
form 409. The printing operation causes loss1 in original analog visible authentication
pattern (oavap) 411 in analog form 409. When authenticator 421 authenticates analog form
409, it makes a digital recording of oavap 411, resulting in loss2. The recording appears as
roavap 415. Authenticator 421 then employs comparator 417 to compare ovap 406 with
roavap 415. The difference between them is the sum of loss1 and loss2. That will be true
when any otherwise undamaged roavap 415 is compared with ovap 405, and a difference of
that size is a dependable indication that analog form 409 is indeed an original analog form.
At 420 may be seen how authentication works with a non-original document. The difference
between the original document and the non-original document is that the non-original
document is not printed directly from original digital representation 403 of the document, but
instead from a non-original digital representation 423 of the document which has been made
by digitally recording an original document 409 (422). As a result of the digital recording,
the non-original visible authentication pattern 425 in digital representation 423 has suffered
an additional loss of information which appears in Fig. 4 as loss3. When non-original
analog form 429 is printed (427) from digital representation 423, another loss occurs in non-
original analog visual authentication pattern 431, indicated as loss4. When non-original
analog form 429 is authenticated by authenticator 421 as described above and moavap 435
made from noavap 431 is compared with ovap 405, the effect of loss3 and loss4 will show
up as a greater difference between ovap 405 and rnovap 435 than there was between ovap

405 and roavap 415. Since noavap 431 in a non-original analog form 429 will always
undergo the additional losses 3 and 4, the larger difference is a dependable indicator of a
non-original document.
Non-original analog form 429 can of course be produced by any photocopying process as
well as by the process of recording the original analog form (422) to make a non-original
digital representation 423 and then printing (427) digital representation 423 to produce non-
original analog form 429. The process of acquiring the image of original analog form 409
and then printing non-original analog form 429 from the image causes additional losses like
those of losses 3 and 4, and consequently, moavap 435 produced in this fashion will still be
less similar to ovap 405 than roavap 425.
Of course, if non-original digital representation 423 is itself made from a non-original digital
representation, rnovap 435 will include the additional losses resulting from the photocopying
or printing and digital recording of that non-original digital representation as well.
Obviously, if loss1 and loss2 were fixed values, the detector could always determine
correctly whether the document is original or non-original. However, in general some
variation will occur for each loss, for instance some originals could be printed with a better
quality (fidelity) than others. It seems then that a statistical approach to detection should be
employed.
Details of a preferred embodiment of the technique for distinguishing between an
original and a non-original document: FIGs. 6 and 7
An authentication technique is only as good as its reliability. The key to minimizing the
probability of detection errors is the method for measuring how "different" a visual
authentication pattern recorded from a document is from the original digital representation of
the visual authentication pattern. The measurement method chosen must be based on
properties of the VAP that are affected by the process of making a non-original document
and must clearly distinguish an original from a non-original document.
Our approach is to consider the photocopying, recording, and printing processes as filters,
more specifically as low-pass filters. Hence, high frequencies will be more attenuated than
low frequencies by the printing and recording processes, and will lose more information at
each record-and-print or photocopying step. For low frequencies in which a record and print
or photocopying process preserves nearly all energy, a VAP in a non-original document may

not have significantly less information the VAP in an original document. The very high
frequencies may also not be helpful, since most of the energy at these frequencies in the
VAP is lost the first time the VAP is |printed. Consequently, even the VAPs of original
documents contain very little information from those frequencies. Therefore, one must make
an appropriate selection and/or weighting, of the frequencies used by the detector. The
selection of frequencies for comparison, as well as the selection of a threshold for
determining whether a document is original or non-original is typically done by training the
comparison software on VAPs from original documents.
It should be pointed out here that the technique described above does not require a special
visual authentication pattern. Instead, the entire document or a part of it can be used as the
pattern. However, because many documents may not contain information at the energy
levels necessary to determine whether a document is an original or a copy, it is better to use a
visual authentication pattern which contains information at the proper energy levels. In the
following, such visual authentication patterns will be termed copy detection patterns, or
CDPs. The information in a CDP is distributed in appropriate frequencies. In a preferred
embodiment, the original digital representation of the CDP is generated pseudo-randomly by
a key, and consequently a program that has access to the key can create a new copy of the
original digital representation of the CDP at any time. This key can be kept secret or revealed
only to trusted parties. The copy detection pattern is inserted or printed on the document to
be secured. In a preferred embodiment, analysis of a copy detection pattern from a document
is done by digitally recording the document's CDP, using the key to generate a new copy of
the original digital representation of the CDP, and comparing the recorded CDP with the
original digital representation of the CDP. In other embodiments, the recorded CDP may
simply be compared with a preexisting copy of the original digital representation of the CDP.
Algorithms used in the technique
This section describes the algorithms used for (1) generating an original digital
representation of a CDP; (2) detecting and extracting a CDP from a document; (3) comparing
the original digital representation of a CDP with a recorded CDP; and (4) determining
whether a CDP is original or non-original. The manner in which the CDPs are compared in
algorithm (4) and the thresholds for determining whether a CDP is original or non-original
are determined by a training process in which algorithm (3) is used to gather training data.

Generating the original digital representation of the CDP
The function make_pattern is used to create a digital representation (pattern_img) of a copy
detection pattern that may be identified with a source of the digital representation from
which an original document is made. make_pattern generates a noisy gray-scale or color
pattern. A black border may also be added to the pattern to facilitate its detection in the
document. The CDP may optionally also display a logo. The logo will typically affect the
lowest frequency bands, and its impact on detection will be therefore limited. Typical values
are given in the explanation of parameters.
pattern_img = make_pattern(type, height, width, key, filename, border, logo_img,
logo_weight).
Parameters for pattern generation
Required:
1. Type: type of generated random number values, e.g. 'randn' (gaussian N(0,1)), 'rand'
(equiprobable distribution), 'randint (binary +1 or -1 distribution), or MD5, SHA algorithms
(0-255 integer number). The random number values are then used to compose a grayscale or
color image.
2. Height: height of pattern in pixels (e.g. 104).
3. Width: width of pattern in pixels (e.g. 304).
4. Key: integer-valued secret key or password used as a seed for the random number
generator.
Optional:
5. Filename: name of the file in which the pattern image is saved.
6. Registration mark (e.g. black border added on the sides of the pattern image, dots added
at the four corners of the pattern image).
7. Logo_img: image to be used as background logo, automatically scaled to the dimension
of the pattern image.
S. Logo_weight: value between 0 and 1 to weight the energy of the logo image (e.g. 0.2),
which is superimposed on the pattern image.

An example of the use of pattern generation algorithm:
1. Generate pattern in a specific domain (e.g. DCT luminance or spatial in color RGB
mode):
pattern = generate_pattern(type, height, width, key);
2. Transform the pattern to the spatial domain if the domain in the Step 1 is not spatial
(e.g. inverse DCT):
pattern _img=transform(pattern);
3. If required round up pixel values p to integer values 0

4. Combine logo with pattern, for example, the mixing following function can be:
pattern_img=(1-logo_weight) *pattern_img+ logo_weight*logo_img;
5. Add registration mark (e.g. black border).
6. Dump image.
A pattern image may consist of multiple components/channels such as Red, Blue, Green, or
YUV, which can be produced as described in Steps 1 and 2 above.
To combine a CDP with logo or background image, various mixing functions can be
adopted. For example when the CDP is merged with a barcode (image), the CDP replaces
only the black area of barcode and leave the white areas untouched.
Any shape (such as circle, oval) of the pattern image can be generated. A simple approach is
to use a "shape mask" which defines an arbitrary shape represented by a two-dimensional
array consisting of "1" and "0". Any shape can be created by applying the "shape mask" to
the rectangle pattern image.
Detecting and extracting the VAP from a document
In this implementation, a digital recording of the document being authenticated is made and
the black border on the VAP is used to locate the VAP in the digital recording. The black
border results in a strong variation of luminance in the transition region, which is easily
detectable. Other techniques for determining the location of the VAP may be used as well
(egg existing features in the documents, black dots, etc.). Once the VAP has been detected, a
digital representation is made of it which is comparable with the original digital
representation of the VAP. This digital representation is the recorded VAP.
The original digital representation of the VAP and the recorded VAP are compared using the
following function, that measures an index that indicates Row "close" the recorded VAP is

from the original digital representation of the VAP. The original digital representation of the
VAP can be stored in the memory of the detector, or can be re-generated if the parameters
used to create the original digital representation and the function make_pattern(..) are
available to the detector. The optional parameters used when combining the pattern with a
logo may not be required, because the logo generally affects the properties of the pattern
only slightly. The function for doing the comparison is analyze_pattern, which returns
Results, and may take different parameters depending on the scenario that is actually applied:
Results = analyze_pattern (type, height, width, key, ... , test_img);
OR
Results = analyze_pattern (orig_img, test_img);
Parameters and output:
1. type, height, width and key: these are as explained for pattern generation.
2. testjmg: test pattern image extracted from the document.
3. origjmg: original digital representation of the pattern
4. Results: contain all the results of the analysis For example, it may include different
measures of correlation or statistics, computed for different elements of the images eg
different frequencies, different areas, different color channels, etc.)
The following example shows the steps of the algorithm the original digital pattern is
regenerated and the subfunctions required for the algorithm:
1. (Optional) Remove the black border from the test CDP
2. Transform the test pattern image into the domain in which it was originally
generated, for example, 8x8 block DCT: test_pattern=transform(test_img);
3. Regenerate the original CDP:
pattern = make_pattern(type, height, width, key);
4. (Optional) Locally synchronize the test CDP with the original CDP as described
below. (Optional) Apply certain image filters (such as sharpening) to the test CDP in
order to produce a better correlation with the original CDP.

5. If required, convert the original CDP and test CDP into the domain where the
comparison is to be made (eg 8x8 block DCT). Note that the comparison can be made
in more than one domain, for example in both the spatial and frequency domains.
6. Compute several measurements of similarity between the original CDP and the test
CDP for each channel in the transformed domain. For example, if patterns are
generated and recorded in the color RGB domain, and the analysis is made in the 8x8
block DCT domain. Then there are 192 (i.e. 8x8x3) combinations by means of which
the two patterns can be compared, and hence 192 measurements of similarity can be
performed. The measure of similarity can itself be computed in several ways, for
example by binning values and keeping only the one where there is a higher
correlation, in order to exclude areas of the test CDP that may have been corrupted.
7. Collect and combine all similarity measures or measures based on other image
features, in order to measure one or more indices of quality or of the "closeness" of
the test CDP to the original CDP. The combination function can be any function that
combines the different inputs, for example a function that combines similarity
measures by assigning more weight or importance to features that are better
discriminants between the original CDP and the test CDP.
As already explained above, a duplication process will always degrade the original CDP, and
in general it is expected that the different measures of closeness or quality will be lower for a
CDP that is recorded from an analog form. However, due to statistical variations, an
adequate selection and combination of the different measures can be more effective in
determining whether a test CDP is recorded from an original analog form or from a non-
original analog form..
FIG. 6 shows the correlation (shown at 605) between the energies of the frequencies in the
original CDP and the test CDP from the document being authenticated for thirty bands of
frequencies (shown at 603). As expected, the correlation between the energies is highest in
the low frequency bands from which little information is lost in the copying process and
lowest in the high frequency bands where even a single printing operation causes the loss of
most of the information. If the correlations are substantially lower in the middle frequency
bands than they would on average be for CDPs from original documents, the CDP is not an
original, and therefore neither is the document being authenticated. That is the case for the
plot of FIG. 6, which thus shows that the document being authenticated is not an original.

Other image features can also be considered when the correlation values by themselves arc
not sufficient to determine whether a document is an original analog form or a non-original
analog form. Additional image features which can be used for producing correlation values
between the original CDP and the test CDP include :
- color histogram
- edge, line and outlines
- frequencies in other domains (such as Fourier and Wavelet domains)
- brightness and contrast
Detecting whether a CDP is from an original or a non-original document
The function detect_pattern analyzes the results returned by analyze_pattern and returns the
value Output, which indicates whether a CDP is from an original document or a non-original
document.
Output = detect_pattern (Results, Parameters)
Results: can be a scalar value or a vector, the output of the function analyze_pattern.
Parameters: values required to adjust the behavior of the detection function, which may
depend on the requirements of the application and the conditions under which it performs
detection.
Output: different output values are possible. In its simplest form, Output may take three
values: ORIGINAL, NON-ORIGINAL, or PROCESSING-ERROR. The last output may
occur when the pattern is badly recorded. Output may return more detailed information, for
example, NON-ORIGINAL can further indicate how the test pattern from the non-original
document was produced (eg duplication, photocopy, regeneration, etc.). Output can further
provide indexes of quality or closeness.
Here is an example of the algorithm for a simple detection function:
1. Combine the various Results values returned by analyze_pattern to obtain a scalar
value S. One way of doing this would be to make S by summing the returned Results.
2. If S> T1 then output is ORIGINAL, else if S>T2 then output is NON_ORIGINAL,
else the output is PROCESSING ERROR.

Here T1, and T2 are two scalar parameters typically obtained via a training process, with
typically T1>T2.
Local resynchronization of the CDP from the document with the original CDP
In order to compare the CDP recorded from the document with the original CDP, the
recorded CDP must be synchronized with the original CDP. One way to do this is to use
synchronization points in the recorded CDP, for example, black border 601, to synchronize
the original. Once the CDPs are synchronized, the comparison between them is done pixel-
by-pixel or block by block.
When there have been errors in printing the CDP in the document or in the digital recording
of the CDP from the document, the CDPs cannot be perfectly synchronized by this method.
For example, there might be less than a pixel shift between the original CDP and the one
recorded from the document. Furthermore, the shift may vary along the pattern: in some
cases the upper part of the recorded CDP may be shifted downward compared to the original
CDP and the lower part be shifted upward (or vice-versa, of course). These shifts may be
very hard to notice, may not occur consistently, and may vary locally in the recorded pattern.
They are generally caused by slight instabilities in the printer, but can also be caused by
similar instabilities in the recording device.
These unpredictable sub-pixel shifts may reduce the detector's performance: because of
these misalignments, some CDPs from original documents may be detected as being from
non-original documents. One method of handling these "pathological" CDPs from original
documents, and in general of improving the stability of the CDP detection is to locally
resynchronize the CDPs in order to correct the local misalignments. There are several ways
to perform local resynchronization, but the general idea is to use the recorded CDP itself for
local resynchronization.
One way to perform local resynchronization is to divide the original CDP into blocks (non-
overlapping blocks are preferred, but the blocks could also overlap) and find which block of
the recorded CDP has the closest match with a given block of the original CDP. If there were
no misalignment, the block of the recorded CDP that most closely matched the given block
would be at the same position in the recorded CPD that the given block had in the original
CDP: for example, the best match for the 10x10 block with starting position (80,80) and
ending position (89,89) of the original CDP would be the corresponding block (80,80) to

(89,89) of the recorded CDP. However, if there is a misalignment, the best match could as
well be with block (81,80) to (90,89) (shift of one pixel to the right). If that is the case,
then the recorded pattern will have the block (81,80) to (90,89) shifted 1 pixel to the left, to
position (80,80) to (89,89). The same idea can be applied to each block in the recorded CDP,
to produce a "locally resynchronized" CDP.
Local resynchronization requires a couple of parameters and functions. First, we must define
a measure of distance between each block of the original CDP and a block of same
dimensions of the recorded CDP. A convenient measure for this purpose is the standard
correlation coefficient. It is also necessary to set the dimensions of the blocks into which the
original CDP is divided: typically a block of dimension 8x8 or 16x16 can be used, but in
general blocks of size NxM can be used. As mentioned earlier, blocks can be overlapping, in
which case the amount of overlap between successive blocks needs to be defined. Another
parameter to set is the search range or search area: starting from matching positions, how far
should the algorithm look for a matching block? This is set with a parameter n, where for
block starting at position (x,y) of the original CDP, all blocks with position (x+/-i,y+/-i) ,
0 It is also possible to scale the digital and recorded CDPs before doing local
resynchronization: this allows a finer grain match. For example, by scaling the two CDPs by
2, we can recover half pixel shifts. And finally, the synchronization algorithm can be applied
iteratively on the resynchronized CDP until no further improvement is found.
Once the resynchronization is performed, an arbitrary measure of similarity/distance between
the resynchronized recorded CDP and the original CDP can be performed. A simple
correlation, or a local frequency analysis can be performed, perhaps with parameters based
on a training set. These measures, which typically make an average of certain quantities on
the whole CDP, may however not always be robust against some local damage to the
scanned CDP that may occur in certain applications. For example, in some cases one area of
the CDP may have been badly printed, or may have been damaged by scratches, writing, or
water. In other cases the scanning device may have inserted distortion into the scanned CDP;
that problem typically occurs with feed-through devices when the document is not correctly
inserted. To make the CDP more robust against these kinds of distortion, more robust
measures of similarities may be used: one such measure is the median local correlation
coefficient, where a correlation coefficient is computed for each block of the CDP, and the
median of all local correlation coefficients is computed. Here, computing a median instead
of an average makes the detector significantly more robust to local alterations. To cope with

a larger amount of corrupted areas in the CDP, it is also possible to compute the average of
only the 20% best local correlation coefficients, which can be assumed to be non-corrupted.
In one implementation, this procedure of computing is this sort of "biased" average is
applied separately to each frequency channel, and optionally to different color channels. Of
course, the foregoing synchronization techniques can be applied not just with CDP's, but
with any recorded visible authentication pattern that needs to be synchronized with an
original visual authentication pattern.
Applications of CDPs
CDPs can be used in any situation where it is useful to distinguish an original document
from a non-original document. A CDP may be printed by any process which prints the CDP
with sufficient fidelity so that a digital recording of the CDP is comparable with the original
digital representation of the CDP. The pattern may be particularly adapted to detect non-
original documents made by particular photocopying, scanning, or printing techniques.
Particular uses of CDPs include:
1. Printing a CDP on packaging for brand protection
2. Printing a CDP on checks and currency for copy detection
3. Printing a CDP on valuable documents including certificate, contracts, and the like for
verifying whether the document is the original or a copy.
4. Printing a CDP on holograms
5. Printing a CDP on labels on valuable goods such as aviation/automobile parts or
pharmaceuticals.
More generally, a CDP may be used in any application where it is desirable to be able to
determine what processes have been applied to a document. The pattern may of course be
varied as required to best detect the processes of interest.
CDP can also be used for the following applications:
1. Benchmarking of printing quality
When reading the CDP, a quality index of the digital recording of the CDP is computed. This
quality index will vary on printing quality, paper/substrate quality, or digitization/scanning

(device) quality. The CDP quality index can then be used to quantify the quality of a certain
printing process, a certain substrate or a certain scanner.
2. Quality control
In the same vein, a CDP reader can be used in a printing production process for automatic
quality control. The advantages of the CDP over manual inspection is that it gives an
automated, objective, and precise measure of quality.
3. Tracing
The CDP has a structure and characteristics that is associated with the printer, paper, camera,
and usage and wearing. In principle, analysis of the CDP can determine the general "history"
of the document: how it was printed and what "wear and tear" it has suffered.
Using visible authentication patterns to detect alterations in documents: FIG. 10
Certain classes of documents are always "modified" after they are printed. One common
example of this is a check that is printed with blank fields that are filled in when the check is
written. A problem with documents belonging to all of these classes is that what is placed in
the filled-in fields may be altered later. Thus, even though the check itself is authentic, the
semantic values of what was written in the blank fields may be changed. For example, a
payee of a check can modify the amount on a check that is addressed to him (e.g. from "one
hundred" to "nine hundred"), in a way that is difficult for a teller to notice.
This kind of problem is hard to solve because the forgers do not actually create counterfeit
documents; instead, they alter the semantic value of authentic documents. The problem is
made harder by the fact that the filled out authentic document already contains legal
modifications. The problem is, how are the legal modifications to the document to be
distinguished from later illegal modifications.
One of the solutions to this problem is forensic examination. If the teller suspects that the
check has been modified, he can bring it to another authority for further examination.
However this task is manual, costly, and time-consuming and it is clearly not possible to
apply it systematically to every document or check. Often, the counterfeiter forges a check
by first erasing a part of the writing. For example, to modify the amount from "two hundred"
to "nine hundred", he will probably erase the "two" and modify it to "nine". To erase
handwriting, he will often use chemical products. Another possibility is to scrape the
original amount from the check, repaint the background, and then write in the new amount.

Visible authentication patterns can be used to detect these illegal modifications. The general
idea is to print a VAP in each of the areas of the document where we may want to detect
illegal modifications. The legal modifications are then made by writing on the VAP. The
precise, unique and uncopyable VAP structure can be used later on to detect modifications
and to determine if the modifications are acceptable. The idea is that both writing on a VAP
and erasing something written on a VAP produce detectable modifications of the VAP.
Writing on the VAP destroys the pattern, as does scraping writing off of the VAP or
applying a chemical erasing agent to the VAP. A VAP{ that is used in this fashion is termed
in the following a modification detection pattern, or MDP.
How a MDP may be used to detect illegal modifications can be summarized as follows:
• insert an MDP in each area of the document which needs to be protected against
unauthorized modifications.
• When verifying the authenticity of the document, first record an image of each of the
MDPs in the document.
• for each recorded MDP, compare the recorded MDP with the original digital
representation of the MDP to detect areas where the MDP has been damaged.
The results of the comparison of the recorded MDP with the original digital representation of
the MDP can be used in a number of ways:
• Display the results of the comparison with the damaged areas highlighted to a decision
maker. This will show both the areas that contain writing and the erased areas.
• Display the results of the comparison with non-written damaged areas highlighted to the
decision maker.
• Compare the size of the damaged area with the size of the area that has been written on,
and if the difference is above a threshold, treat the field has having been modified.
FIG. 10 shows how a MDP can be used to detect modifications. At 1001 is shown a MDP
1002 that is used in an amount field for a document. As before, MDP 1002 is surrounded by
black border 106. As shown at 1003, the amount 250 has been written into MDP 1002. At
1005 may be seen how a forger has modified the amount $250 to the amount $950 by
erasing the "tail" of the 2 and adding a loop to make it into the number 9, To cover up the
erasure, the forger has imitated the pattern of the MDP. The imitation is still visible in 1005,
but even as shown, it is good enough to get by a harried teller and a skilled forger can easily
make the imitation better.

The problem for the forger is that the erasure has destroyed the MDP. By scanning the MDP
and locally analyzing it, it is possible to detect with high accuracy which part of the MDP
has changed from the original. Erasures can be detected by finding areas in the MDP which
neither contain neither text nor the original pattern. This is shown at 1009. Text areas are
easy to find because they are typically color-uniformed and darker than the MDP. All that
then need be done to find the erased areas is to compare the areas of the recorded MDP that
do not contain text with the original digital representation of the MDP. The erased areas
show up as parts of the recorded MDP that do not match the original digital representation,
as shown at 1011. In a preferred embodiment, such non-matching parts appear in red.
A few more details on the algorithm for using an MDP to detect alteration of a document:
• Making MDPs: A MDP may be made in any way that a VAP is made, but then the pixel
values are increased to make the MDP brighter (otherwise, the text written on the MDP
could not be easily distinguished from the MDP).
• Use registration marks (e.g. black border or corner marks) to extract the recorded MDP
from the document.
• Detect text areas: A low-pass filter is applied to the recorded MDP, and pixels with
values under a threshold are considered to be part of the text and legal modifications.
• Detect modifications of the MDP: after local resynchronization is applied, a correlation
coefficient is computed for each block of the MDP. As shown in 1009 one can see that
the areas of the text and the areas of the illegal modification were altered.
• By excluding the legal modifications (at 1003) from image 1001, several algorithms can
be applied to detect the illegal modifications. One possible way is to first classify areas
into modified or non-modified (by thresholding the local correlation), then apply a noise
processing algorithm or low-pass filter that removes individual or non-significant
modified areas. Region detection algorithms can also be applied to find significant
modified regions. The result is displayed in 1009: the non-allowed modifications are
displayed in red, while the allowed one (on the text) areas displayed in green.
• Depending on the amount of non-allowed modifications, a decision can optionally be
taken on the authenticity of the document to which the MDP belongs..
Implementation details of the VAP

Form of the VAP in the document
All that is required for using a VAP to detect alterations in an analog form is that there be an
area in the analog form that has a pattern which will serve the purpose and an original digital
representation of the pattern that can be compared with the pattern as recorded from the
analog form. It will thus be possible in some cases to use a preexisting pattern in an analog
form for the technique. More usually, though, the VAP will be included as part of the design
of a new analog form. There is of course no need to hide the VAP in the analog form, and
indeed in some cases, its presence may be advertised to reassure customers that illegitimate
analog forms can be detected. On the other hand, the VAP can have any shape, and thus can
easily be built into other features of the analog form. FIG. 11 shows two examples. Ar 1101
is shown a barcode whose bars make up the VAP. At 1103 is a logo which contains the
VAP. There may of course be more than one VAP in a document and more than one VAP
may share a location. This can be done by giving each pattern a weighted value such that the
weights of all of the patterns sum up to one, e.g.:
Final_pattern=a*pattern1+(1-a)*pattern2, where 0 One application of multiple patterns would be the authentication of contracts, where each
party adds its own pattern when it signs the contract or otherwise terminates a stage in the
negotiations.
It is also possible to insert several CDPs on a document at different places, typically
produced with different keys, to enable multiple parties to verify their own CDP without
being able to verify the CDP of the other parties (and consequently being able to duplicate
them). It is even possible to generate a CDP using different keys (each key may control
different spatial or frequency area of the CDP), to enable different parties to verify the CDP.
This way, if one party releases his key, this key is not sufficient to make an exact duplication
of the CDP (all keys are necessary), and the security is not compromised. This is analogue
to the concept of "Shared Secrets".
Registration of the VAP
The preferred embodiment employs black box 106 as registration for the VAP. However,
many other registration techniques are possible. For example, one could use visible patterns
such as frames, bar codes, or the like already displayed on the package to locate the VAP, as
well as OCR. One can also use UV marks or any techniques discussed in the parent patent
application USSN 10/287,206, J. Zhao, et al., Apparatus and methods for improving
detection of watermarks in content that has undergone a lossy transformation, filed

11/4/2002. Also, one could also make the Fourier-Mellin transform of the recorded VAP and
match it with the VAP's original digital representation.
For some applications, it is difficult to know if the orientation of the digital recording of the
VAP is correct, or if it should be flipped upside down (180 degrees rotation) before reading.
To avoid having to analyze the VAP one time, and then, if the analysis is not successful, to
rotate it in the opposite vertical orientation and analyze it again, it is possible to design a
symmetric VAP: the lower part is a mirror of the upper part. The VAP can then be analyzed
independently of its vertical orientation.
Properties of the VAP's pattern
The pattern can be a grayscale pattern or it can be a colored pattern. In the latter case,
different color channels can be employed, for example RGB and YUV. The pattern can also
be generated in various frequency domains, for example spatial, wavelet, DFT, or DCT
domains.
Generating the VAP
The noisiness, i.e., random nature, of the VAP is what makes it difficult for counterfeiters
and forgers to deal with it. Any technique which can produce a random or pseudo-random
pattern will do to generate the VAP. In the preferred embodiment, generation is done by
providing a value to a pseudo-random number generator which generates a sequence of
random numbers that is unique for the value. The value thus serves as a key which may be
used to generate new copies of the pattern. Different pseudo-random number generators may
be used in different embodiments and the probabilistic frequency values for the generated
random numbers can be taken from different probability distributions. The key can also be
used to determine the locations in the VAP upon which analysis is performed. As will be
explained in the discussion of using the VAP to carry other information below, the key may
include such other information. In some applications, the key used for designing the pattern
may not be revealed to other parties. In that case, any useful way of distributing keys may be
used, for example asymmetric keys or public-private key pairs.
The pattern may be combined with a logo, either by adding the logo to the pattern or vice-
versa. The logo can be any existing image or document, including images serving other
purposes (a 2-D bar code, a watermarked image, etc.). It is also possible to apply any
process such as filtering to the pattern or to the logo in such a way that the logo will

minimally interfere with comparing the recorded VAP with the original digital representation
of the VAP.
Printing the VAP
The quality of the authentication provided by a VAP depends completely on the fidelity with
which the VAP is printed on the document. Authentication errors can be reduced if a
"quality control" step is added at the end of the printing process to guarantee the fidelity of
the VAP:
1. each printed VAP will be passed to an automatic verification process to check if
the authentication pattern has the minimum quality which is required for it to be
recognized as an original.
2. If the quality is below the minimum quality, an alert will be issued and the
document/package containing the authentication pattern will be re-printed.
3. Such verification can also serve as a "quality control" for printing quality or
errors introduced by the printer.
The generation of the VAP can be adapted to the printing technology. For example, if a laser
printer printing only binary dots is used, then a binary dot VAP can be generated to better
use the possibilities of the printer. Also, a VAP might be more adequately generated, and
printed, in the color space of the printer. If a certain printer uses specific inks (eg CMYK), it
can be more effective to generate the VAP in that domain than in the RGB domain. If the
VAP is engraved in metal with a laser engraver able to produce only binary dots, then it
would make more sense to generate a binary VAP.
Using the VAP to carry other information
Three approaches to using the VAP to carry other information are discussed in the following:
reserving certain areas of the VAP to hold information, using the other information to
generate the key used to make the original VAP, and adding a watermark to the VAP. The
disadvantage of adding a watermark is that it reduces the ability of the VAP to detect non-
original analog forms or modifications in the VAP.
Reserving areas in the VAP to hold information
Certain areas (e.g. 8x8 blocks) of the VAP can be reserved to hold information. In those
areas, the structure/characteristics of the VAP is not actually used to verify its authenticity,

but to store some bits of information. These areas can be selected pseudo-randomly using a
key, such that an entity which does not have the key cannot determine whether an area in
VAP is actually used to store information or to determine the authenticity of the VAP. In an
area that is used to hold information, a certain structure/characteristics of the VAP can
correspond to a certain bit value ('0' or '1') of information. This bit-dependenl
structure/characteristics can of course vary as determined by the key. Note that the reserved
areas and the information they contain are part of the VAP as generated. They thus do not
degrade the ability of the VAP to detect unauthentic documents. One use of the reserved
areas it to store the key used to generate the VAP.
Using the information to generate the VAP's key
This discussion uses the following terminology: The VAP is created and detected with a key
P; we may want to use a different key S to embed a message in the pattern as described
either above with regard to the reserved areas or below with regard to watermarks; a message
M is embedded in the VAP using the key S; finally additional information / might be printed
visibly on the document (serial number, barcode, etc.), or UV-coded invisibly, within the
pattern or outside of it, or be obtained from an external source.
Fixed pattern key
In one embodiment, the VAP creation key is fixed P. This is typically the case for standard
offset printing technology, where the printing technology does not have the ability to change
the pattern dynamically for each package/product/document. The key can be kept secret as
described above or may be incorporated into other security features. For example, it could
be printed in UV inks on the document. The fixed pattern key can be used for brand
protection or document protection generally.
Variable pattern key In another embodiment, the VAP's key depends on a secret key S and
some other information /. This other information / may be displayed on the document
(within the pattern or outside of it) or obtained from an external source. The information
from the document can be for example a serial number, a text, a barcode etc. Information
from an external source may for example be a value that is associated with the VAP and
known to the person who is checking whether the document containing the VAP is authentic.
The pattern key may be any arbitrary function P=f(S,I) of the parameters that are the secret
key and the information I. A simple function would be to concatenate or sum the two
parameters, but many other functions are possible, such as a hash value of a combination of

the two parameters, etc. At detection time, the printed information I is extracted with an
appropriate technology - bar code reader, OCR, etc-. Then the pattern key is generated as
P=f(S,I), and the pattern is analyzed. Typical uses include brand protection with digital
printing.
Watermarks in the VAP
It is possible to embed a visible or invisible watermark in the VAP using any watermarking
technique. The watermark may serve multiple purposes. It may contain any information,
including only a single bit, as described above, or aid registration of the pattern. The
watermark can either be detected with the key used to generate the VAP or with another key
such that its reading is restricted to another user or group of users. A third possibility,
explained below, is to use the message carried by the watermark to derive the key used to
generate the VAP.
When a digital watermark is embedded into to a VAP, the VAP will be slightly modified. As
a result, when the same VAP is used for authenticity verification, its reliability for that
purpose may be reduced. As an alterative, the digital watermark can be embedded into areas
in the VAP that are reserved to store information as explained above.
Watermarks and keys
In another embodiment, the pattern creation key P is derived from the secret key S and the
message M embedded as a digital watermark in the copy detection pattern. In this case, M
takes the place of the information I used to create the variable pattern key discussed above.
At creation time, the pattern key P can be any function of the secret key S and the message
M, g(M,S). The pattern is generated in the usual way, then a watermark is inserted into the
pattern, where the watermark encodes the message M using the secret key S as a parameter.
At detection time, first the watermark message M must be read from the pattern with the
secret key S. Once M is known, the pattern key P=g(M,S) is derived, and the pattern is
analyzed.
In this application framework, no auxiliary technology would be needed to extract more
information printed on the package. It is however possible to also use the information I
printed on the package in several ways within the principle described here. For example, the
secret key S can be used in combination with the information I to produce a watermarking
key W, i.e. h(S,I)=W, which is used to embed the message in the pattern. Then the pattern
key is generated in the same way as before, P=f(M, W)=f(M,h(S,I)). In general, VAPs may

be combined with watermarking technology and other reading technology (OCR or barcode
readers, for example), are to produce different levels of verification.
Comparing VAPs
How recorded VAPs are compared with original digital representations of VAPs will depend
on how the VAP is made and what its purpose is. Some generally-applicable variations
include evaluating certain areas independently, either to have more clues on what process has
been applied to the document or for security features. As described above, a VAP may
contain more than one authentication pattern, and the different patterns may be analyzed by
different groups.
Before VAPs can be meaningfully compared, the comparison program may have to be
"trained" with VAPs recorded from original documents, as described above for CDPs. The
training establishes the thresholds for determining whether a VAP recorded from a document
whose authenticity is being examined is authentic or not. The meaning of the threshold will
of course depend on the kind of alteration that the VAP is being used to detect. Retraining is
required whenever the manner in which the original documents are printed varies in a
manner which affects VAP comparison. Training can be done automatically by printing a
number of VAPs on a sheet of paper, scanning the sheet, and providing the scan to training
software.
In another embodiment, instead of comparing the digital recording of a test VAP to a
corresponding digital representation to measure its quality index, it is possible to compare
the digital recording to a digital recording of another VAP (typically an original VAP that
was scanned).
Environments in which VAP analysis is performed
What is required to do VAP analysis is a device that can record the VAP from the document
to make the recorded VAP, a copy of the original digital representation of the VAP, and a
processor which can compare the recorded VAP with the original digital representation of
the VAP. The recorder and the processor may be local to one another or connected by a
network. The network may be either a local area network (LAN) or a wide area network
(WAN). An example of a local environment is a processor is a PC that has a scanner, a copy
of the analysis code, and a copy of the original digital representation of the VAP. The copy
of the original digital representation of the VAP may either be downloaded or generated
locally using a key. Results of the analysis are output to the PC's display device.

In a network environment, scanning, analysis, and the original digital representation of the
VAP may be distributed across the network in any fashion. A distribution that maintains the
security of the original digital representation of the VAP and simplifies the equipment
needed at the local level is one in which scanning is done in a device which is connected to a
WAN. When the VAP on the document has been scanned to produce the recorded VAP, the
recorded VAP is sent to a location in the WAN at which both the analysis code and an
original digital representation of the VAP are available. The original digital representation
may be either stored or regenerated on demand. The analysis is done at that location and
only the result of the analysis is returned via the WAN to the device used for scanning. In
network environments generally, information carried in or sent with the recorded VAP may
be used to retrieve information for use in the analysis. For example, the document may
contain a serial number, and the serial number may be sent with the recorded VAP to the
location that does the analysis. If there is an association between VAPs and serial numbers,
the serial number could be applied to a database at the location or elsewhere in the network
to retrieve the either the key for the original digital representation of the VAP that should be
compared with the recorded VAP or a copy of the original digital representation of the VAP
itself. As described above, the serial number could be specified in a barcode that contained
the VAP, as a visible watermark in the VAP, could be OCR'd from the document, or even
could be input by the person doing the scanning.
A camera (webcam, camcorder, etc.) can be also used to capture images of the VAP. In this
case, the VAP detector receives not only one image as input, but a constant stream of
images. The additional information provided by several images can potentially be very
useful in the analysis. However, as the time required to analyze one image can be
significantly larger then the time between two successive images, the use of the stream of
images can be optimized. For example, images that appear to have the properties for a
correct reading (good sharpness, VAP wholly contained in the picture), can be selected from
the stream and used for analysis.
Combination of VAPs with other security technologies
A VAP can be combined with other technologies targeted at making analog forms more
secure. For example, the VAP can be used with information hiding techniques such as digital
watermarking, with machine-readable information such as 1-D or 2-D bar codes, with
holograms, or with any other technology that can be applied to an analog form. The

relationship between technologies can be multifarious: as an example a 2-D bar code can
contain independent information, or the secret key needed for the pattern analysis, or
inversely, the VAP can hold the key required for decoding the 2-D bar code or the 2-D bar
code can contain the VAP.
Conclusion
The foregoing Detailed Description has disclosed to those skilled in the relevant
technologies the inventors' techniques for determining whether an analog form of an object is
an original analog form or a non-original analog form, their techniques for using VAPs to
perform authenticity checks on analog forms, and their techniques for using VAPs to hide
messages in analog forms and has further disclosed to those skilled in the relevant
technologies the best mode presently known to the inventors for practicing the techniques. It
will be immediately apparent to those skilled in the relevant technologies that many
embodiments of Applicants' techniques other than those disclosed herein are possible. For
example, the size, shape, and pattern of a VAP will be determined by the nature of the analog
form the VAP is being used with and by the VAP's purpose. How a VAP carries additional
information and what that information is will also be determined by the nature of the analog
form and by the VAP's purpose. In general, VAPs may be used in any situation in which
changes made after the original analog form is made are to be detected. While the application
discloses VAPs printed on documents, analogues to these printed VAPs may be placed on
analog forms in other media.
For all of the foregoing reasons, the Detailed Description is to be regarded as being in all
respects exemplary and not restrictive, and the breadth of the invention disclosed here in is to
be determined not from the Detailed Description, but rather from the claims as interpreted
with the full breadth permitted by the patent laws.

WE CLAIM :
1. A method of determining whether an analog form of an object is an original
analog form, the method comprising:
creating an original digital pattern containing an authentication pattern;
then producing at least one original analog form from the original digital
pattern causing a first loss of information in the at least one original analog form;
making a digital recording from at least a portion of the at least one original
analog form or from at least a portion of another analog form derived from the at
least one original analog form causing a second loss of information in the
recorded portion;
comparing the digital recording with a corresponding portion of the original
digital pattern to perform an authenticity check at an authenticator thereby using the
sum of the first and second loss of information to determine a degree of
dissimilarity between the digital recording made form the portion and the
corresponding portion of the original digital pattern; and
using the degree of dissimilarity to determine whether the recording was
made from that at least one original analog form or from the other analog form.
2. The method as claimed in claim 1, wherein:
the method is practiced in a node in a network and
the method further comprises:
receiving the recording from another node in the network, the digital
recording being made from the at least one original analog form or from the other
analog form.
3. The method as claimed in claim 1, wherein:
the method is practiced in a node in a network and
the method further comprises:
returning an indication to another node whether the digital recording has
been determined being made from the at least one original analog form or from the
other analog form.

4. The method as claimed in claim 1, wherein:
the method is practiced in a processor to which a digital recording device
and an output device are attached; and
the method further comprises:
making the digital recording from input received from the digital recording
device; and
providing an indication whether the digital recording has been determined
being made from the at least one original analog form to the output device.
5. The method as claimed in claim 1, wherein:
in the step of determining a degree of dissimilarity, what is determined is
dissimilarity of features in the digital recording of the portion and the original digital
pattern of the portion, the dissimilarity being caused by operations comprising
digital recording and printing involved in making a non-original analog form.
6. The method as claimed in claim 1, wherein:
the original digital pattern of the portion has a noisy pattern which is
perceptible in the analog form by humans.
7. The method as claimed in claim 6, wherein:
the noisy pattern is made using a key and
the method further comprises:
using the key to generate the original digital pattern.
8. The method as claimed in claim 6, wherein:
the noisy pattern has a function in the analog form in addition to permitting
determination of whether the analog form is the at least one original analog form.
9. The method as claimed in claim 8, wherein:
a message may be derived from the noisy pattern.
10. The method as claimed in claim 9, wherein the method further comprises:

using the message to derive a key; and
using the key to generate the corresponding potion of the original digital
pattern.
11. The method set forth in claim 9, wherein:
the message is in portions of the noisy pattern reserved therefor.
12. The method as claimed in claim 8, wherein:
at least part of the noisy pattern is in a background image.
13. The method as claimed in claim 8, wherein:
at least part of the noisy pattern is in a barcode.
14. The method as claimed in claim 1, wherein:
the result of the step of comparing indicates a portion of the recorded
authentication pattern that has been destroyed in the recorded analog form.
15. The method as claimed in claim 1, wherein:
the result of the step of comparing indicates a portion of the recorded
authentication pattern that is from the at least one original analog form.
16. The method as claimed in claim 1, wherein:
the authentication pattern further contains a message.
17. The method as claimed in claim 1, wherein:
the result of the step of comparing indicates a portion of the authentication
pattern that has been overwritten by written text.
18. The method as claimed in claim 1, wherein:
the original digital pattern is an image and the step of producing at least one
original analog form comprises printing the image on the object.

19. The method as claimed in claim 18, wherein:
the original digital pattern is a grayscale image or a color image.
20. The method as claimed in claim 1, wherein:
creating an original digital pattern comprises creating an original digital
representation of a document;
further comprising:
printing the document to produce the at least one original analog form.

Documents:

1853-kolnp-2004-abstract.pdf

1853-KOLNP-2004-AMENDED PAGES.pdf

1853-kolnp-2004-assignment.pdf

1853-kolnp-2004-cancelled document.pdf

1853-KOLNP-2004-CANCELLED PAGES-1.1.pdf

1853-kolnp-2004-claims.pdf

1853-KOLNP-2004-CORRESPONDENCE 1.1.pdf

1853-KOLNP-2004-CORRESPONDENCE 1.2.pdf

1853-kolnp-2004-correspondence-1.3.pdf

1853-KOLNP-2004-CORRESPONDENCE.pdf

1853-kolnp-2004-description complete.pdf

1853-KOLNP-2004-DRAWINGS-1.1.pdf

1853-kolnp-2004-drawings.pdf

1853-kolnp-2004-examination report.pdf

1853-kolnp-2004-form 1.pdf

1853-KOLNP-2004-FORM 13.pdf

1853-kolnp-2004-form 18.pdf

1853-kolnp-2004-form 3.pdf

1853-kolnp-2004-form 5.pdf

1853-KOLNP-2004-FORM 6.pdf

1853-KOLNP-2004-FORM-27.pdf

1853-kolnp-2004-gpa.pdf

1853-kolnp-2004-granted-abstract.pdf

1853-kolnp-2004-granted-claims.pdf

1853-kolnp-2004-granted-description (complete).pdf

1853-kolnp-2004-granted-drawings.pdf

1853-kolnp-2004-granted-form 1.pdf

1853-kolnp-2004-granted-form 2.pdf

1853-kolnp-2004-granted-specification.pdf

1853-kolnp-2004-intenational publication.pdf

1853-KOLNP-2004-OTHERS 1.1.pdf

1853-KOLNP-2004-PA.pdf

1853-KOLNP-2004-PETITION UNDER RULE 137-1.1.pdf

1853-kolnp-2004-petition under rule 137.pdf

1853-KOLNP-2004-REPLY TO EXAMINATION REPORT-1.1.pdf

1853-kolnp-2004-reply to examination report-1.2.pdf

1853-kolnp-2004-reply to examination report.pdf


Patent Number 247001
Indian Patent Application Number 1853/KOLNP/2004
PG Journal Number 12/2011
Publication Date 25-Mar-2011
Grant Date 24-Mar-2011
Date of Filing 06-Dec-2004
Name of Patentee SCHREINER GROUP GMBH & CO. KG
Applicant Address BRUCKMANNRING 22, 85764 OBERSCHLEISSHEIM
Inventors:
# Inventor's Name Inventor's Address
1 ZHAO JIAN 130 NEW ROAD, RUMFORD, RI 02916
2 PICARD JUSTIN 16 MAYFLOWER STREET, PROVIDENCE, RI 02906
3 THORWIRTH NIELS 549 HOPE STREET, #2, PROVIDENCE, RI 02906
PCT International Classification Number G06 9/00
PCT International Application Number PCT/US2003/15168
PCT International Filing date 2003-05-14
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10/287,206 2002-11-04 U.S.A.
2 60/380,189 2002-05-14 U.S.A.