3
Emerging Counterfeiting Technology Threats

Current digital image capture and reproduction technology has evolved rapidly in recent years, resulting in the affordability of highly capable desktop systems for the home consumer market. Most home users want to take a picture with their digital camera or scan an image with their scanner and then print out a faithful reproduction of the original. While very good images can be readily obtained today, faithful reproductions are not so easy or repeatable; color-management tools are thus available in image-processing software for delivering good color reproduction. A skilled user can match colors easily, and complex image-processing tools are becoming accessible even to casual users. The digital technology revolution has had a concomitant effect on the capabilities accessible to the counterfeiter. As discussed in Chapter 1, this increase in capabilities and access to them provide a major motivation for this study. The charge for the study (see Appendix A) requests the committee to make an assessment of technology threats with respect to U.S. currency. This chapter describes the current state of the art for, and possible future innovation in, relevant image capture and printing. The chapter also discusses the implications of the identified technology threats for U.S. currency.

DIGITAL COUNTERFEITING

The counterfeiting of currency, or indeed other documents, employs each of the three major steps involved in digital imaging: (1) capturing the image, (2) processing the image, and (3) printing the image. These three steps of digital imaging may be carried out in either binary or analog mode, and there are also



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A Path to the Next Generation of U.S. Banknotes: Keeping Them Real 3 Emerging Counterfeiting Technology Threats Current digital image capture and reproduction technology has evolved rapidly in recent years, resulting in the affordability of highly capable desktop systems for the home consumer market. Most home users want to take a picture with their digital camera or scan an image with their scanner and then print out a faithful reproduction of the original. While very good images can be readily obtained today, faithful reproductions are not so easy or repeatable; color-management tools are thus available in image-processing software for delivering good color reproduction. A skilled user can match colors easily, and complex image-processing tools are becoming accessible even to casual users. The digital technology revolution has had a concomitant effect on the capabilities accessible to the counterfeiter. As discussed in Chapter 1, this increase in capabilities and access to them provide a major motivation for this study. The charge for the study (see Appendix A) requests the committee to make an assessment of technology threats with respect to U.S. currency. This chapter describes the current state of the art for, and possible future innovation in, relevant image capture and printing. The chapter also discusses the implications of the identified technology threats for U.S. currency. DIGITAL COUNTERFEITING The counterfeiting of currency, or indeed other documents, employs each of the three major steps involved in digital imaging: (1) capturing the image, (2) processing the image, and (3) printing the image. These three steps of digital imaging may be carried out in either binary or analog mode, and there are also

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A Path to the Next Generation of U.S. Banknotes: Keeping Them Real hybrid processes and steps that can be done in various combinations. Binary and analog images both have advantages and disadvantages. Producing an image in a binary system requires patterning the image in such a way as to make it appear to have gradations. However, on close inspection, this type of pattern is revealed to be dense on-and-off spatial patterns, with each pixel printed with either ink or no ink. Analog printing produces images with an array of elements that have different optical densities. Hybrid systems draw from both paradigms, but the results tend toward the artistic rather than the production of multiple images that are all closely identical. Images that appear on Federal Reserve notes (FRNs) can be acquired using a variety of digital scanning and photographic equipment—complemented with sophisticated art software—that offers very cost-effective capture of images with good quality. Table 3-1 summarizes the committee’s analysis of the usefulness of security features in deterring counterfeiting that uses digital age tools. The committee anticipates that the capabilities of digital imaging will improve over the next 5 years. This chapter describes the expected improvements in digital imaging technology and how these improvements are likely, in the committee’s opinion, to affect the capabilities of the classes of counterfeiter described in Chapter 2. TABLE 3-1 Summary of the Committee’s Analysis of the Usefulness of Current (2006) Security Features with Significant Deterring Value in the Production Rate of Digital Age Counterfeiting Features Ink-Jet Printer All-in-One Device Color Copier Flatbed Ink-Jet Printer Digital Press High-Quality Scanner Imaging Software Human perceptible               Substrate ● ● ● ● ● NA NA Tactility (or feel) ● ● ● ●   NA NA Watermark ● ● ● ●   ● ● Security strip ● ● ● ●   ● ● Intaglio printing ● ● ● ●   NA NA Offset color blending               Optically variable ink ● ● ● ●   ● ● Intaglio microprinting   ● ●         Offset microprinting   ● ●         Colored threads               Machine readable               Paper fluorescence ● ● ● ● ● NA NA Magnetic ink pattern ● ● ● ●   NA NA Infrared ink pattern ● ● ● ●   NA NA NOTE: “●” indicates some deterrence value; “blank,” low or no deterrence value; “NA,” not applicable.

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A Path to the Next Generation of U.S. Banknotes: Keeping Them Real IMAGE ACQUISITION To replicate an FRN using digital technology, a counterfeiter must first transform an analog object, the physical note, into a digital format. U.S. currency is approximately 2.5 by 6.0 inches. Therefore, the scanned image of a U.S. banknote from a 3,000 pixel per inch (ppi) scanner would require about 7,500 by 18,000 pixels, or a total of 135 million pixels. This file size is now well within the capabilities of even lower-priced home copiers and amateur flatbed scanners. Table 3-2 provides a summary of the committee’s analysis of the capabilities of image-capture systems and relative costs. The majority of the printed features on FRNs are binary, meaning that at every pixel element, ink is either deposited on the substrate or it is not. Virtually all of today’s high-quality printing processes are also binary.1 However, each pixel of an image from an input scanner is usually recorded with at least 8 bits, or 256 levels of intensity. When the image is prepared for printing, however, the bit depth is reduced again to 1 bit because most electronic printers are binary devices. Most often, because halftoning or similar techniques are used to generate the appearance of gray in the image that is printed, the sharp binary image is lost in the transition to analog and back again. Flatbed input scanners costing a few hundred dollars or less can now scan at high quality, at reasonable speed, and with spatial pixel densities up to 43,000 ppi using a single silicon sensor chip that has sufficient sensors to cover the entire page image—resolution of 3,000 ppi requires about 25,000 sensors to cover an image 8½ inches wide. This resolution is more than adequate to capture most printed material very well, especially with some postprocessing of the image to enhance fine features. Increasing the scanning density beyond current capabilities is unlikely, because improved scanning pixel density is not needed for most applications and because the commercial profitability of flatbed scanners is not high enough to warrant large investments for specialty or niche applications—increasing this density would require costly improvements in optics and data storage. A scanning resolution of up to 4,000 to 5,000 ppi is currently available on the best graphic arts scanners. These scanners are often referred to as copy-dot scanners because they attempt to copy all of the halftone dots in the original. Thus, advances in image capture in such devices will not improve image acquisition for counterfeiting because the resolution is at a practical limit already. Today, digital cameras cannot provide the image quality of a flatbed scanner owing to many optical effects as well as to limited pixel density. But digital cameras, including those in cellular telephones, will certainly continue to improve, and 1 Photographic film and thermal dye printers, being analog rather than binary technology, are two exceptions.

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A Path to the Next Generation of U.S. Banknotes: Keeping Them Real TABLE 3-2 Summary of the Committee’s Analysis of the Capabilities of Digital-Image Capture Systems Capture Device Resolution (pixels per inch) Cost Comments Digital camera Varies Low to high Limited number of total pixels available Simple consumer-grade reflective flatbed scanner 2,500 Low Ideal for counterfeiting owing to high quality and low cost High-quality reflective flatbed scanner 2,500-4,000 Moderate High quality with only moderate cost Professional drum scanner 4,000-5,000 High High cost presents barrier to entry Artwork software No limit Free to moderate Time-consuming and limited to use by experienced artists performance-for-cost will significantly increase in the next few years. Nevertheless, these improvements are not likely to provide the counterfeiter with any additional or lower-cost capabilities than those currently available from other technologies. IMAGE PROCESSING Once an image has been captured, it must undergo a number of processing steps before the best possible reproduction can be made. The steps are these: Removing scanning artifacts such as dust specks; Adjusting the brightness and contrast of the image; Performing color adjustments; Applying software filters to enhance edges and sharpen the image, often called unsharp masking; and Rotating the image if it has been scanned at a small angle. Digital image processing of FRN images can be done using a wide variety of software tools, ranging in cost from free to very expensive. Achieving expert results with such software is at the present time highly dependent on the skill of the user. Current Capabilities One of the significant improvements in image processing has come about through generally available software. Packages such as Adobe Photoshop, Micro-

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A Path to the Next Generation of U.S. Banknotes: Keeping Them Real soft’s Digital Image Pro, and others provide powerful tools for improving and enhancing digital images. Personal computer (PC) operating systems also are sold with image tools that can be accessed by the most casual user. The capabilities of the very-low-cost tools are expected to increase with new operating system releases. The growing demand for accessible digital photography tools makes image processing a very rich area of innovation that will be available to the counterfeiter. Additional tools available through online photo-sharing Web sites can easily—and anonymously—improve the reproduction of color images. An option for any counterfeiter would be to inspect the currency visually and then to re-create it line by line using software illustration programs; this would be a painfully slow process, even though it would allow great detail to be reproduced well. Bitmap editing, or pixel-by-pixel editing, of a captured image can be done using very inexpensive software such as Microsoft Paint, but this too would take a tremendous investment in time and a good dose of eyestrain to generate a useful image. The labor content of such an approach is not expected to abate in the next 5 to 10 years. An alternate approach is to re-create an FRN feature by feature; programs such as Adobe Illustrator, Adobe Photoshop, Adobe PageMaker, QuarkXpress, and others provide a rich set of tools with which to generate exceptionally high-quality images. In addition, these programs can leave the created or re-created data in a form that allows “resolution-independent” printing options—meaning that the quality of the output is materially dependent on the quality of the printer. Using an illustration program in this manner is analogous to engraving a false duplicate by hand. The scanning of sharp lines such as those found in intaglio printing is a particular challenge. Often, the images of lines scanned at angles or lines that are wavy or that possess other artistic features will not necessarily reproduce with uniform thickness in an image. When printed, the lines can vary by a pixel or so, which can be quite visibly apparent under certain circumstances. Often such lines need to be retouched to remove problematic artifacts. Software to perform this task automatically is under development and has the potential to greatly reduce the labor cost of making high-quality images and to eliminate the need for special skills and additional steps. To prepare an image for most digital printing, the scanned image needs to be converted to a binary format. The scanned image can be halftoned,2 as in conven- 2 Halftoning is the transformation of a grayscale or color image to a pattern of small dots with a limited number of colors—that is, just black dots for grayscale images or a combination of cyan, magenta, yellow, and black dots for color images—in order to make the image printable. In the basic case of gray scale, the halftone process creates patterns of small black dots on a white background. When viewing such an image from a sufficient distance, the human viewer cannot see the dots themselves because they are too small. Instead, the human viewer has the illusion of seeing gray, whose

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A Path to the Next Generation of U.S. Banknotes: Keeping Them Real tional printing, or it can be made without halftone patterns using an on-off process often referred to as thresholding. While technologies are in development, it seems that the practicalities of binary printing processes will be limiting for some time. The use of masking software, automated subroutines, and other such software shortcuts can greatly reduce the amount of work required of a determined counterfeiter who uses current image-acquisition technology. Artistic design software is improving to the extent that each generation of upgrades makes it easier for the skilled user to reproduce complex effects in the scanned image. In addition, software that seeks to reproduce the look of traditional art materials has advanced by leaps and bounds in the past few years and continues to improve. These developments may threaten one of the most counterfeit-deterring features of U.S. currency—the feel of the intaglio printing. Emerging Capabilities Image processing will no doubt be an area of significant development in the next 5 or 10 years. The modern PC can now readily handle gigabyte-size images, more than enough storage for the captured image of an FRN scanned at 4,000 pixels per inch. Because capture quality is already at a high level of fidelity, image processing can be used to enhance the scanned image and can enable high-quality printing. However, most of the software available today, while having somewhat sophisticated automated tools, delivers the best results when it is in the hands of experienced users. In the next 5 years, much of what occurs today in application software may be incorporated in the scanner or operating system. The growth of the digital imaging market will require that such capabilities be close to automatic. A few years ago, one could do a very good job of processing color film and prints at home. To do so required a darkroom, chemistry, some basic photoinstrumentation, and a lot of experience if it was to be done well. As is clear from any number of trends, the darkroom is now digital, and today’s experienced digital imaging enthusiasts are constantly improving their skills. However, like their predecessors in chemical photography, most do not “mix their own chemicals”; they use what is commercially available. Several products introduced in 2005 will automatically produce multiple versions of a color-corrected image, requiring the user simply to select the best image from a group. darkness depends on the amount of black dots on the white background. In color halftoning, the cyan separation, the magenta separation, the yellow separation, and the black separation combine in a set of patterns printed over each other, which the human viewer from a distance observes as a color image.

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A Path to the Next Generation of U.S. Banknotes: Keeping Them Real Technology development will result in increasing automation in image processing in the next 5 to 10 years. Techniques such as automatic contrast adjustment, unsharp masking, line-width control, and feature smoothing are all under development as automatic features. The driver for these changes is to make the user’s experience as pleasant and simple as possible. Automatic comparison of the input and output image is currently available in some software packages. Significant improvement is expected in image reproduction because the market will demand it. In 1981, SciTex provided a stunning image-processing system for graphic artists that cost approximately $1 million. Today, systems that dwarf SciTex system capabilities can be purchased along with their host PC for less than $2,000, a 500-fold performance-for-cost improvement. There is no indication that we are nearing the limits of software or computing technology. The ability to use image-processing software to customize individual notes by changing the serial numbers, plate numbers, or other identifiers may enhance the ability to pass a counterfeit note. IMAGE PRINTING Image printing is the final step in digital reproduction except for finishing operations, which would include cutting, trimming, and the addition of simulated security elements. It is also the limiting step in the counterfeiting process. Modern digital printers (see Table 3-3) available to ordinary users can provide quality at or above that available from photochemistry just a few years ago. Some of the improvements that might be expected in printing technology in the near term are discussed below. Electrophotography The electrophotographic process is the basis of the most widely used document-copying machines.3 It begins with a photoconducting surface that is uniformly statically charged. In many copiers, this is a metal plate with a selenium-based coating. The charged surface is then exposed to a pattern of focused light, usually from a laser or light-emitting diode. This pattern is the image to be printed. Where light falls, the charge dissipates and a “charge image” of the light pattern remains on the photoconductor surface. The image is developed by dusting the charged surface with a pigmented powder, called toner, which is attracted to the charged areas of the pattern. The powder is then transferred electrostatically to paper and, finally, the toner is fused to the 3 Xerox Corporation was the principal investor in electrophotography in the early days of this technology, which became more commonly known as “xerography,” apparently a catchier name than electrophotography.

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A Path to the Next Generation of U.S. Banknotes: Keeping Them Real TABLE 3-3 Summary of the Committee’s Analysis of Some Printer Technologies and Capabilities Technology Resolution (μm) Cost Comments Electrophotographic (laser) 7-10 Low Potential primarily for low-volume counterfeiting Ink jet 7 Low Attractive for all classes of counterfeiters owing to low cost and high resolution Thermal 2 Low Limited by low-image-quality substrate chemistry requirements Chemical NA High High cost, variable quality, and limited availability of adequate substrate materials Photographic NA High Produces quality similar to that obtainable with ink-jet printers but at a higher cost NOTE: For the cost of equipment acquisition, “low” refers to the cost for a typical peripheral for a home computer and “high” is outside this range; “NA,” not applicable. paper with heat. A continuously rotating metal drum moves the plate and paper through the various steps—charging, exposing, developing, and transferring—in a seamless manner. The quality of electrophotographic images has improved continually since the introduction of this technology in the mid-1900s. The critical elements of electrophotographic technology for counterfeiting are the development, transfer, and fusing steps that control the image quality. Advances in these capabilities have resulted in higher quality and lower cost. In the development of the image, in which the toner material forms the text and images on the printed paper, the size of the toner particles controls the print resolution. As first implemented, particle size in toner averaged about 12 micrometers (μm). In order to improve image resolution to 600 dots per inch, the particle dimension was reduced to 8 μm and the uniformity of particles was improved. Further reductions in size will be necessary for improvements in resolution. Toners that are substantially smaller than this are not only hard to manufacture properly but also are difficult to keep confined to the printer itself—that is, they can be become airborne. Toners with particles as small as 1 or 2 μm can be made, but they can be hazardous if they become airborne and are inhaled by users. Advances in the materials properties of toner can also help improve resolution during fusing and transfer. By varying the chemistry of the polymer in the toner, printed images can be made to look more like ink on paper rather than having the look of electronic printing. The quality of the fusing techniques can have serious implications for durability. The fusing techniques of lower-cost printers often are

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A Path to the Next Generation of U.S. Banknotes: Keeping Them Real not as durable as those of the faster, more-expensive machines. Folding or creasing of the print can cause poorly adhered toner to flake off at the crease, thus exposing the white substrate and producing an obvious defect. As fusing technology improves, home printers could have the potential to do one-pass, two-sided printing. This means that the registration of the images on the two sides of the substrate can be significantly better than that achieved by removing the printed sheet, flipping it over, and reinserting it for printing of the second image. A variation of electrophotographic printing is liquid electrophotographic (LEP) technology. Digital printing presses using this LEP technology have micron-sized toner particles, enabling resolutions finer than those typically possible with dry-toner devices. LEP devices are being developed to rival offset presses for applications such as marketing brochures and photograph albums and so are advancing the limits of color reproduction and line art. Existing products do not typically have provisions for highly accurate front-and-back registration. While the quality of electrophotographic products is expected to improve in the next several years, significant engineering challenges remain that will limit the performance of these systems. Improvements in ink-jet printing, the major market competitor for lower-cost electrophotographic printers, will, however, continue to drive print quality. Ink-Jet Printing While ink-jet printers predominate in the home printer market, they are also capable of producing some of the highest-quality images of any type of printer. An ink-jet printer is any printer that shoots extremely small droplets of ink onto paper to create an image. The droplets form small dots on the printed page. These dots can range in density from 10 to 30 dots per millimeter. The placement of the dots can be very precise. Ink-jet technology is particularly useful because registration in the system is an electromechanical issue that can be solved by straightforward engineering methods and techniques. For this reason, flatbed ink-jet printing has the greatest potential for future use in home printing of high-registration, simultaneously printed front-and-back images. One disadvantage of this method is ink bleeding into the paper, resulting in a blurry appearance on some types of paper. These effects may be pronounced with certain types of paper, especially when the ink is water-soluble. The introduction of ultraviolet-curable, water-impervious ink-jet inks would solve the problems of stability, lightfastness, water solubility, dot gain, and spread. Ink-jet printers fall into three categories: continuous, thermal, and piezoelectric ink jet. Their features and applicability to counterfeiting are described next.

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A Path to the Next Generation of U.S. Banknotes: Keeping Them Real Continuous Ink Jet Continuous ink jet is one of the oldest ink-jet technologies in use. It is fairly mature and arguably produces the best-quality image obtainable on any type of printer. Continuous ink jet is actually better than photography in many cases in reducing image noise. Continuous ink-jet printers are not, in general, printers for home use. They are often large and require a fair level of maintenance and operator skill to attain top performance from the device. In continuous ink-jet technology, a high-pressure pump directs liquid ink from a reservoir through a microscopic nozzle, creating a continuous stream of ink droplets. One of the advantages of continuous ink-jet printing is the very high velocity of the ink droplets, which allows the ink drops to be thrown a long distance to the target. Another advantage is freedom from nozzle clogging, as the jet is always in use. Another key advantage of continuous ink-jet printers has been their ability to produce small drops of ink that can be repeatedly printed at the same or carefully adjacent spot to vary the effective droplet size. This capability produces stunning quality. It is not expected that continuous ink-jet printer technology will move significantly forward in use in the next 5 to 10 years for two reasons. First, they are inherently complex to maintain and operate. Second, newer ink-jet printers or other types are now approaching the same quality levels attainable using continuous ink-jet technology. Thermal Ink Jet Thermal ink-jet printers, also known as bubble-jet printers, are widely available for home use. These printers operate by rapidly heating a small volume of liquid ink and forcing a steam bubble to form that ejects the ink from an orifice. As the bubble cools, the vacuum created draws fresh ink back into the nozzle. A large investment in this technology has produced a remarkably reliable process. In 2006, the print cartridge is a highly engineered device with 64 or 128 tiny nozzles that are produced using photolithography. To produce an image, the printer runs a pulse of current through the heating elements. Each of the tiny chambers can fire a droplet simultaneously to produce the image. A disadvantage of this technology for counterfeiters is that the ink must be water-based. Such inks are inexpensive to manufacture, but they may perform best on specially coated media that do not have the feel of currency paper. However, because the print head may be produced at less cost than that for other ink-jet technologies, it is a relatively low-cost process. One area of active research and engineering is currently aimed at producing multiple drop sizes on demand. However, it is not an easy task to control the bubble

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A Path to the Next Generation of U.S. Banknotes: Keeping Them Real and its associated heat cycle to produce different-size bubbles reliably. Possible advances in the next 5 or 10 years may also lead to increased process speed. It is not clear at this stage if either of these advances is likely to be realized for home users or only for higher-end users. Piezoelectric Ink Jet Most higher-end ink-jet printers use a piezoelectric crystal in each nozzle instead of a thermal heating element. “Piezo-jet” printers utilize a piezoelectric actuator to produce pressure in the liquid-ink chamber. The pressure and drop size generated by the piezoelectric actuator can be controlled better than in bubble-jet printers and can also produce smaller droplets of ink. These variable-size drops and smaller droplets can generate impressive images. Today, the smallest commercial droplet size available is in the range of 1 picoliter. This corresponds to a drop diameter of about 7.1 μm, or about 3,500 or so drops per inch. Such small droplet sizes are generally not attainable in the bubble-jet schema. However, this very small drop size can be lost on typical paper used for home printing, so it is unknown whether the investment in such improvements would be profitable in the home market over the next 5 to 10 years. An advantage of piezoelectric ink-jet printing is that it allows a wider variety of inks than does thermal or continuous ink-jet printing. The emerging ink-jet material-deposition market uses ink-jet technologies, typically piezoelectric ink-jet, to deposit materials on substrates. Printers that can deposit glues, resins, or waxes onto a variety of substrates have been available since the early 1990s; they are called solid ink-jet or wax-jet printers. While it has advantages in color intensity, solid ink-jet technology has limited droplet size compared with that of bubble-jet or piezo-jet liquid-ink printers because the viscosity of the melted material complicates the jetting of small drops. The piezoelectric ink-jet technology is currently available on commercial flatbed digital presses, and while they are currently very expensive, they are easily and quickly configured for counterfeiting. This is a major departure from the setup time required for commercial printing presses; it could allow counterfeiters who might work in printing shops to use the digital equipment without alerting their management. In addition, advances in this technology in the next 5 to 10 years may mean that this level of quality may be available for consumer units. Advances may also mean that metallic or plastic particles could be “printed” and someday may be able to simulate some non-image features. For these reasons, piezoelectric ink-jet printers may prove to be the most useful technology to counterfeiters now and in the future.

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A Path to the Next Generation of U.S. Banknotes: Keeping Them Real Thermal Printing Thermal printing commonly is done in one of three forms: thermal transfer, thermal dye transfer printing, and custom-substrate thermal printing. Thermal transfer, one of the early printing technologies, has come and gone as a technology of choice. Its main advantage has been its reliability and high edge acutance. However, achieving printer pixel density higher than 1,000 ppi is problematic owing to the requirements for the heater heads. It is not expected that thermal transfer will be able to compete with bubble-jet, piezo-jet, or electrophotographic images as time goes on. The second form of thermal printing, thermal dye printing, has also been referred to as dye sublimation printing. However, in most cases, sublimation is not the physical process that causes image formation, and hence “thermal dye printing” is the preferred nomenclature. Thermal dye is much like thermal transfer, except that instead of transferring material from a ribbon surface to a substrate, dye is migrated from a ribbon and absorbed into a special substrate under pressure. The main advantage of thermal dye is that it can produce true grayscale images without any of the usual halftone patterning or other geometrical structures that trick the eye into seeing gray scale. Such printers produce images very close to those achieved in photography. The main disadvantages of thermal dye are limitations in spatial resolution and speed. Currently, about 600 ppi is the maximum practical density, which is generally low for quality counterfeit currency generation. The third form of thermal printing uses custom chemically treated paper, and it prints with heater heads not unlike those used in thermal transfer. It generally cannot produce good colors, and like the other forms of thermal printing, this technology is generally low quality and is unlikely to improve in the future to any extent. The specialty substrate, in which the chemicals used for image generation are in the paper, would significantly complicate its use for currency counterfeiting. All of these technologies are slow, expensive, and require special substrates to achieve the promised quality. Because none of them is a focus of current industry innovation, concerns about future thermal printing developments with respect to counterfeiting are likely unwarranted. Chemical Printing No imaging process has seen its world grow smaller more quickly than that of conventional chemical photography. Photography can produce outstanding images, but such images are no longer unique to this process. Electrophotographic and ink-jet processes can produce images in many ways as good as those of photography. Because genuine currency is produced in general with commercial processes—offset, intaglio, and letterpress printing—the images are binary, meaning

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A Path to the Next Generation of U.S. Banknotes: Keeping Them Real that each pixel on the banknote either has ink or it has no ink. Hence, photography offers little value over simpler digital processes that are much more reliable and lower in cost. Photography is still of use in the generation of printing plates, but this area is also quickly becoming digital. There is little current activity in either using or improving the quality of non-photographic chemical printing, and it is not expected that this technology will benefit counterfeiters in the foreseeable future. Problems of chemistry control, quality, and maintenance were the factors that killed the early chemical copiers when electrophotographic processes came on the market. These factors are still a barrier to this technology today. Image-Printing Implications Each type of digital printing method discussed above has its own special substrate requirements for optimal image printing. While new substrate capabilities are always emerging, the nature of the various electronic printing technologies restricts the range and types of substrates that work well. These issues are discussed in Box 3-1. The various electronic and other printing processes described above have varied advantages in image quality. The quality of digital presses and advanced electrophotographic printing has risen to the point that it is expected to replace offset printing in the near future. This means that the value of using offset printing as a tool to deter the counterfeiting of the images on banknotes is limited. As is image capture, image printing is now at pixel density levels—2,400 to 3,600 ppi—that are at the limits of human vision. However, improvements in image quality could come from printing images other than in binary mode. Current ink-on-paper printing such as offset and intaglio are binary processes. To simulate the look of gray—as in a watermark—commercial printing devices and most electronic printers print black ink in a patterned fashion. This patterning results in “aliasing” artifacts, because lines are not single strokes but a collection of dots that look at normal viewing distance like single strokes. New approaches in both ink-jet and electrophotographic printers can produce some levels of gray, and multiple gray-level printing could produce dramatic improvements in image quality. In electrophotography, toner particulate size control and toner management as well as fusing technology (which depends on toner chemistry) will continue to set the limits for electrophotography laser printers. Current ink-jet printers must produce only one drop of ink at a time, and each drop must be placed adjacent to the previous drop or drops to produce a line. Such lines often look a bit ragged and do not reproduce intaglio-printed structures well. The size of the ink-jet orifice and the ability to print reliably using small orifices will set the limits for ink-jet pixel density. Inks with multiple densities of the same hue

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A Path to the Next Generation of U.S. Banknotes: Keeping Them Real BOX 3-1 Limitations on Electronic Printing Technologies Regarding Substrates and Additional Elements Most types of paper work well in electrophotographic printers. The two principal restrictions in these printers are the ability of the paper-feeding system to handle the substrate material and the substrate interactions with the electrostatic subsystems such as image transfer and fusing. Many electrophotographic printers can easily handle light- to heavyweight papers, well within the range of currency substrates. Some newer printers can print on both sides automatically, but back-to-front registration of printed features would in general not be nearly as good as that achieved in offset printing. The look and feel of the substrate—including the paper surface, stiffness, and intaglio texture—are difficult for most counterfeiters and technologies to reproduce using current desktop image-reproduction technology. Ink-jet printing can be either more or less tolerant of substrate differences, whereas electrophotographic printers are less sensitive to substrate quality. Paper-feeding requirements are still important, but ink jets can generally feed a wider array of substrate thicknesses. Card stock, shiny or matte finishes, and vellums can be used, because the paper path is usually very short and throughput speeds are low. The only additional requirement of substrates used with ink-jet printers is that they permit the ink to dry and adhere to their surface properly. Liquid ink must to some extent wick into the substrate surface for adhesion. Solid ink is almost substrate-independent, although the quality of the image might vary. Features that affect light transmitted through the substrate—the watermark and security strip—also pose challenges, because most image reproduction is based on reflected light. Banknote features used in machine authentication (e.g., special inks) are difficult to simulate with desktop printing technology. While thermal printers are unlikely to be used for counterfeiting, they may be used as part of a larger system. For example, laser thermal printing could be used to apply special symbols or thin foil features over a previously ink-jet-printed page. Electrophotographic printing can also be used to affix foil or holographic features. may achieve different tones in the image but with much-reduced patterning. This approach has the advantage of using existing transport and mechanical systems and changing only the supply packages for printers in place. Thermal printers can produce excellent vertical or horizontal lines, but their limited pixel density compared with that of electrophotographic and ink-jet printers is expected to render them inferior both now and in the future. Market drivers are a final consideration for high-end printing equipment. One result of gains in desktop technologies and their capability to produce professional-looking results is that small professional printing houses across the country are going out of business and often selling their equipment for as little as 10 percent of its original cost. This may bring a professional setup well within the price range of the petty criminal. With a good computer, a pirated copy of Adobe Photoshop, a digital direct-to-plate machine, and a used Heidelberg press, a petty criminal

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A Path to the Next Generation of U.S. Banknotes: Keeping Them Real with considerable skill might start an offset money-printing workshop in his or her garage. Straight-to-plate technology, in which a computer design can be digitally inked onto printing plates, can turn older equipment into very modern presses. This technology in particular may be a threat because the ease of setup is a significant advantage. Emerging Technologies In addition to the improvements that are expected in current printing technologies, the emergence of some technologies that go beyond image printing may soon overtake those recognized methods. The Convergence of Printing, Manufacturing, and Biology A number of emerging tools use technology invented for printing on paper, but redesigned for other processes. Examples include the high-volume manufacture of microelectronic circuits,4 smaller-volume prototyping processes,5,6 and even printing of biological material to aid analysis.7 Printing-based manufacturing systems offer levels of resolution and registration that significantly exceed the current or projected capabilities of conventional ink-on-paper printers. The target applications for this technology—such as printing flexible electronic circuits—demand very low-cost high-throughput operation, and large-area printing. Goals include rates of 100 square meters per hour, with the ability to process substrates larger than 5,000 square meters with accurate registration. The range of “inks” that can be printed by these systems includes not only the dyes and toners used in conventional printers, but also color-shifting and other optically active inks. Functional materials for the semiconductor elements of thin-film transistors or the electroluminescent layers of emissive displays have also been printed. New ink-jet printing processes can also print “inks” made of a variety of metals, glasses, and plastics, which implies that simple printing processes may be able to simulate non-image features, such as the metallic print on the security strip. Although access to these manufacturing systems is not expected to be widespread, it will increase if their use broadens to more distributed manufacturing 4 Proceedings of the IEEE [Institute of Electrical and Electronics Engineers]. 2005. Special issue on Flexible Electronics Technology. Vol. 93. 5 A.V. Kumar and A. Dutta. 2003. Investigation of an electrophotography based rapid prototyping technology. Rapid Prototyping Journal 9:95-103. 6 See <http://web.mit.edu/tdp/www/whatis3dp.html>. Accessed February 2007. 7 See <http://www.shimadzu-biotech.net/pages/news/1/press_releases/2004_07_23_chip.php>. Accessed February 2007.

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A Path to the Next Generation of U.S. Banknotes: Keeping Them Real systems. It is also possible that some of the features of these advanced systems could migrate into low-cost desktop printers. Some specific technologies in this area include the following: High-speed ink-jet printing in manufacturing systems uses piezoelectric or thermal print heads for high-speed, large-area patterning—up to 100 square meters per hour. These printers involve hundreds of active nozzles, each operating independently, at frequencies of up to tens of kilohertz. Recent work focuses on applications in the manufacturing of display systems and certain components of packages for microelectronics. Large-area, high-resolution displays that use organic light-emitting diodes or circuits patterned by ink jet are possible. Sophisticated control devices enable excellent repeatability in the printing. Machine vision provides the ability to perform registration in real time during printing. Experimental printers are capable of printing droplets with diameters of 5 microns or less, with registration at even finer scales, particularly when patterns of wetting and nonwetting regions on the substrate are used to confine the printed droplets. The range of inks that can be printed is broad. Screen printing uses a squeegee-type blade to push viscous inks through patterned openings in a screen mesh. Existing applications include the low-resolution patterning of decals, signs, and textiles. Screen printing is also commonly used to define some features on printed circuit boards. Recent developments indicate that improved printers and screens can achieve resolution near 10 to 20 μm with good registration. Laser-induced thermal transfer printing uses a focused laser beam to selectively transfer layers of solid-material “inks” from a “donor” sheet to a target substrate. The basic printing mechanism is similar to that of a conventional thermal transfer printer. The use of lasers in place of resistive heaters, however, can improve the resolution significantly, to levels that are comparable to the spot size of the laser, near 2 μm. The overlay registration is as good as the resolution. Large areas and high patterning speeds are possible with rigid and flexible substrates. Inks range from electroluminescent organics, to metals, to colored and black dyes, to semiconducting polymers, to carbon nanotube composites, to biological tissues. The most well-developed potential applications of this printing technique are for the production of organic light-emitting display devices, and color filters for liquid-crystal displays. In the latter case, the printed material consists of stacks of charge transport and emissive layers. In the former, dye-doped polymers are used. Ink-jet printers can print a wide range of materials in addition to those commonly used for printing images. The “inks” include liquid suspensions of nanomaterials, such as carbon nanotubes and buckyballs, colloidal particles,

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A Path to the Next Generation of U.S. Banknotes: Keeping Them Real nanoparticles, and nanowires—metals and semiconductors, with magnetic and dielectric properties. Biomaterials, including deoxyribonucleic acid, or DNA, have also been printed. Active materials—semiconducting or light-emitting materials—as well as passive dielectric and photocurable polymers are also printable. Many of these unconventional inks might be used to simulate features, such as optically variable images, that appear on currency. Ink-jet technology can also be used to pattern classes of materials that are themselves not directly printable. In these cases, printed polymers or waxes may be used as sacrificial masking layers for patterning other materials. After use, these layers can be removed. In this way, both positive and negative patterns can be produced by ink-jet techniques. IMPLICATIONS OF TECHNOLOGY TRENDS In summary, and referring back to the classes of counterfeiter identified in Chapter 2, primitive counterfeiters do not use the types of digital technology discussed in this chapter, but create counterfeits using little more than manual artistry to modify a piece of currency in order to increase its value and obtain financial gain. Opportunist counterfeiters counterfeit occasionally and use typical desktop computer equipment and available crafting supplies, sometimes in creative ways. Petty criminals counterfeit in a dedicated manner and actively invest in specialized computer equipment and materials. Professional criminal counterfeiters focus the efforts of a large group of people on the sophisticated production and distribution of counterfeits. State-sponsored counterfeiters may use the very same high-precision equipment that the government uses to manufacture banknotes. Table 3-4 summarizes the committee’s analysis of the digital technology access of the four classes of counterfeiter that use digital technology. TABLE 3-4 Summary of the Committee’s Analysis of Digital Technology Access, by Class of Counterfeiter Class Ink-Jet Printer All-in-One Device Color Copier Flatbed Ink-Jet Printer Digital Press High-Quality Scanner Imaging Software Opportunist ● ●       ● ● Petty criminal ● ● ●     ● ● Professional criminal ● ● ● ● ● ● ● State-sponsored Not applicable—reproduces government processes directly. NOTE: The primitive class is omitted from this table as it does not use digital technology. Within each counterfeiter class in the table, additional nondigital techniques may be used to improve note simulations—for example, craft supplies to reproduce features that use color-shifting ink. “●” indicates high likelihood of access; “blank,” low likelihood of access.

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A Path to the Next Generation of U.S. Banknotes: Keeping Them Real The committee has shown that innovation and skilled engineering will continue to improve the range of excellent, reliable, and cost-effective image capture and printing technology for consumer use over and above what is already available at very affordable prices—although some physical limits may dominate the possible improvements in image quality. As the cost of imaging equipment goes down and print quality goes up, the use of this type of equipment by the opportunist counterfeiter will expand. The same equipment will enable expanded operations by petty criminals, and it may make counterfeiting more lucrative for professional criminals as well. The trend means that the protection against counterfeiting afforded by a two-dimensional printed image casually viewed in reflected light is highly diminished. Therefore, the committee concludes that image-capture, processing, and reproduction technologies, both current and predicted, pose a significant threat to the security of FRNs. Emerging technologies will continue to limit the ability of any two-dimensional printed image to deter widespread counterfeiting successfully. Images involving other classes of features—images viewed in transmitted light, light-reflecting features, or other complex optical features—offer a substantial challenge to primitive and opportunist counterfeiters and a costly barrier to petty and professional criminal counterfeiters. But there is also another technology threat, not related to the hardware of image capture and printing but nevertheless a significant, pressing, and perhaps more insidious threat—that is, the augmentation of the counterfeiter’s skills owing to improved communication available via the Internet. Counterfeiters today can easily search online for raw materials and surplus high-quality printing equipment. This search capability, coupled with the ability to purchase these materials and equipment from global sources via the Internet, accounts for an important and growing threat. Information itself is also a precious commodity for the counterfeiter. The information shared around the globe today may include ideas for simulating currency features, novel concepts for combining processes to create a better counterfeit, or expertly processed image files. Successful information sharing may also create new distribution networks for counterfeits. Such network-coordinated distribution would require law enforcement to be at least equally well networked in order to discover and stop it. CONCLUSIONS The Internet remains a growing threat to the security of U.S. currency owing to the ability it affords counterfeiters to augment their knowledge base of how to simulate and reproduce the look and feel of Federal Reserve notes.

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A Path to the Next Generation of U.S. Banknotes: Keeping Them Real Image-capture, -processing, and -reproduction technologies, both current and predicted, pose a significant known threat to the security of Federal Reserve notes. The security of FRNs often depends solely on the casual viewing of two-dimensional printed features in reflected light, notwithstanding the deterrence value of the feel of the note, security strip, and watermark. Future innovations in flatbed scanners and other methods for capturing images are not likely to be an area in which technology will further aid the counterfeiter in the next 5 or 10 years. Scanning quality along with the capture of color features and other image characteristics is already adequate for many counterfeiting activities. Printer technologies, including low-cost thermal ink-jet printers for home use and other ink-jet printers and electrophotographic printers, produce counterfeits that can be passed, even though the notes are poor reproductions. However, piezoelectric ink-jet printers may prove to be quite useful to counterfeiters as they provide a noticeable improvement in print quality. Improvements in consumer-grade scanners may occur. These new scanners are likely to further enable the opportunist counterfeiter to close the quality gap with today’s professional criminal counterfeiters. In the future, substantial improvements in the automation of image-processing algorithms are expected to help the less-skilled user process images like a graphics expert. Automated capabilities such as line-width control, uniform image appearance, and color balance would enable an ordinary user to easily obtain an optical image that is very faithful to the original. Emerging technologies are targeted at improvements in desktop capabilities; these improvements will continue to limit the ability of any two-dimensional printed image to deter widespread counterfeiting successfully. The convergence of printing, manufacturing, and advanced materials technology may offer significant new capabilities to professional counterfeiters in the future.