Joel Zlotnick, Tyra McConnell and Traci Moran
Counterfeit Deterrence Laboratory
Office of Fraud Prevention Programmes
Bureau of Consular Affairs
US Department of State

Introduction
Microprinting (also known as microtext) is among the most widely adopted document security features in use today, and like all security feature technologies can be used in ways that enhance or limit its security functionality. Some advantages of microprinting include its low cost, extreme design flexibility, versatility across printing methods, easy integration with other security features and its compatibility with a wide variety of security document types. But microprinting is also subject to some important limitations, such as a disposition to quality control problems, the necessity of magnification for inspection, the difficulty document users can experience in attempting to locate microprinting in an unfamiliar document and (in many implementations) limited effectiveness against traditional counterfeiting attacks. The question explored by this paper series is how microprinting can be optimised to exploit its advantages and/or mitigate its disadvantages. As is often the case in security printing, the answers are design and press capabilities.

To begin, this first paper describes font and artwork options for microprinting, while the second and third papers address colour gamut and microprinting placement, respectively. The strategies described are presented for informational purposes and may or may not be appropriate for specific security document applications or manufacturable by all security printers. 

Throughout this paper, example microprinting graphics are displayed as pairs, with the left image captured at lower magnification (usually 10X) to show context in the document and the right image (usually 18X) to show the microprinting design in greater detail. 

Tiny fonts
Microprinting was first used in security documents long before inexpensive home/office colour printing devices became readily available, but its popularity surged in the 1990s as digital counterfeiting became widespread. Essentially, microprinting was intended to exploit differences in technical capabilities between genuine document manufacturers and counterfeiters with limited graphic arts skills and access to limited digital printing techniques. Specifically, the offset and intaglio printing processes used by genuine security document manufacturers are capable of printing sharp and clear spot colour and line art text, even at font sizes too small for most individuals to read without magnification. Because tiny details are beyond the resolution limits of many inkjet and toner devices (which rely on halftones and process colour to simulate line art and spot colours) available to typical digital counterfeiters, many digital counterfeits can be identified by inspecting microprinting or other document artwork with magnification. If the microprinting is blurry and unreadable, or composed of coloured dots, the document should be regarded suspicious. 

This view is considerably simplified for many reasons. Readability assessment is subjective and dependent on document user training. Microprinting can be prone to quality control problems that produce blurry microprinting even in genuine documents if production standards are not met. Sophisticated traditional counterfeiters with access to offset and/or intaglio printing technology have always been able to mimic readable microprinting and other subtle art. Further, inkjet printers continue to improve, with higher resolutions and smaller droplets. Because specifying how small text must be before a consumer printer can no longer produce a readable simulation is a constantly moving target dependent on many factors, some designers incorporate microprinting of two or more sizes as shown in Figure 1, or microprinting of dynamically changing size as shown in Figure 2, into a single design.  Smaller microprinting may be more difficult for counterfeiters to simulate but larger microprinting is easier to inspect, so use of multiple sizes in a single design may capture advantages of each and can be achieved at low cost.

Figure 1: Two-plate offset microprinting containing larger maroon microprinting juxtaposed with smaller orange microprinting, showing two discrete font sizes incorporated into a single design and with the design repeated in alternating lines.
Figure 2: Multicolour intaglio microprinting incorporating a dynamically changing font size, with the design repeated in alternating lines.

For these reasons, size alone may not be adequate to measure the security value of microprinting against either digital or traditional counterfeiting. If size is not the only appropriate criteria, microprinting should be revisited to identify what other metrics exist (for example, microprinting artwork, colour and placement) and how those can be optimised alongside size. 

Microprinting colour and placement are relevant topics to be addressed in later papers but are out of scope here. The following sections explore how both fonts and macro microprinting patterns can be designed to combat traditional counterfeiting in addition to digital counterfeiting.

Digital and traditional counterfeiting
Digital and traditional counterfeiting follow two basic workflows (or hybrid workflows that combine elements of each). Generally, digital counterfeiters can capture most visible document artwork in a single scanning step. This workflow is fast, easy and obviates the need to redraw individual plate images, but counterfeit quality is limited because digital printing technologies like inkjet can only simulate line art and spot colours using halftones and process colour. In contrast, sophisticated traditional counterfeiters can use true line art and spot colour just as is done in genuine security documents, but this requires many additional prepress steps, including the isolation of individual printing plate images from a target genuine document followed by the tedious and technical process of artwork replication. In short, traditional counterfeiters need to replicate security artwork but digital counterfeiters do not. 

From this perspective, resolution may be the most important factor for microprinting security in the context of digital counterfeiting, but in traditional counterfeiting this necessary process of artwork replication makes font and artwork design relevant to impeding traditional counterfeiting workflows. Replication of microprinting by traditional counterfeiters can be made more difficult if both the microprinting font and/or the macro microprinting design are highly customised. Microprinting cannot be absolutely secured against sophisticated traditional counterfeiters with advanced graphic arts skills, but it can be implemented in genuine documents in ways that increase counterfeiting difficulty.  Some strategies are discussed below.

Font design
Artwork origination by genuine designers and artwork replication by traditional counterfeiters are two different processes. Genuine designers build a design from scratch on a blank canvas, but counterfeiters must work backwards from an existing design. Security document artwork that resists traditional counterfeiting does not necessarily have to be hard for genuine document designers to originate but should be difficult for a counterfeiter to replicate. This topic is complex and cannot be discussed comprehensively here, but many strategies commonly used for other types of security document artwork can also be extended to microprinting designs. Two pertinent points might include use of 1) proprietary instead of public artwork and 2) nonrepeating patterns that cannot be easily counterfeited using step-and-repeat processes.

Regarding the first point above, in the microprinting context “proprietary artwork” could mean design of a distinctive proprietary font instead of a publicly available font. A proprietary font cannot be easily counterfeited just by selecting the exact font from a software dropdown menu and typing vector text, and can force traditional counterfeiters to either replicate microprinting artwork by manual redrawing (as would be necessary anyway for non-microprinting line art designs) or substitute a non-proprietary font for the proprietary font and accept a greater risk of detection. Alternately, even a public font can be customised by making it bold as in Figures 3 and 4, or italicised as in Figure 5, changing the kerning between characters as in Figure 6 or leading between lines as in Figure 7, changing the baseline between adjacent characters as in Figure 8 or use of any of the many other software techniques that can be applied to vector artwork fonts. Hypothetical examples could be envisioned that use all these techniques simultaneously in a single microprinting design; for example, incorporating multi-size variable bold and variable italic characters in lines with varying leading and kerning, and so forth.

Figure 3: Intaglio microprinting with alternating bold/non-bold text, with the design repeated every four lines.
Figure 4: Offset split fountain microprinting incorporating four discrete levels of bold numerals in both positive and negative. Except for a lateral shift, each line contains similar artwork.
Figure 5: Two-plate offset split fountain microprinting incorporating italicised characters in some positions. Though printed from two plates, the microprinting artwork is repeated every four lines.
Figure 6: Offset microprinting with kerning varied to increase spacing between characters. The design repeats every four lines.
Figure 7: Offset microprinting with leading varied to create two regions of microprinting that differ by the spacing between the lines. The characters in every line are otherwise the same, though each line contains two discrete font sizes.
Figure 8: Offset microprinting with the baseline height changed between adjacent characters. Each line of text is angled, but the bottom of each character is parallel to the bottom edge of the image. Much of the artwork is repeated between lines.

The examples in Figures 3 through 8 are composed largely of repeated microprinting artwork, so traditional counterfeiters need only replicate a small portion of the design and then apply step-and-repeat techniques to scale the small area up to a larger pattern. Returning to the second point above, the most effective security designs incorporate continually changing patterns that cannot be counterfeited using step-and-repeat techniques. In the context of microprinting, one way to create a “non-repeating pattern” is by modifying each character in a unique way, such as by changing the shape of characters between lines of different font size so that one line of replicated text cannot simply be copied and enlarged (or reduced) to generate the others, as in Figure 9. Similarly, changing the position of bold characters within lines of otherwise identical repeating text makes each line a little different from the others, prevents easy step-and-repeat counterfeiting processes, and nominally increases the time and effort required to counterfeit the design, as in Figure 10. Justification of lines affects the spacing between characters and can be combined with changes to character width, such that character width can be related to the number of characters in the line, as shown in Figure 11. 

Figure 9: Offset microprinting incorporating changes in size that correspond to changes in font design. Comparison of letters between lines shows that character shape changes as font size changes.
Figure 10: Offset microprinting incorporating several levels of bold text. This pattern would require more work to replicate than lines of text of the same design because the location and boldness of the characters changes between lines.
Figure 11: Justified offset microprinting, where the justification changes not only the kerning but is also paired with subtle changes in the size or width of characters in a few locations.

Figures 9 through 11 illustrate some ways font-level microprinting customisation can prevent traditional counterfeiters from using step-and-repeat techniques. These font-level techniques may be the main type of customisation possible for certain implementations of microprinting, such as single lines of microprinting in bearer signature lines of identity or travel documents. But strategies that can be applied to an entire multiline microprinting pattern, like baseline curvature or distortion, offer effects that are hard to replicate using font vector artwork techniques on individual characters. 

Curvature and distortion
The font-level customisation of individual characters described in the prior sections can be differentiated from customisation of larger artwork patterns because the two design methods require traditional counterfeiters to perform different kinds of artwork replication. Specifically, genuine document art that is either designed by hand to be non-repeating or which is converted from repeating artwork into non-repeating line art (for example, a security halftone) can force traditional counterfeiters to work harder. This is also true of microprinting. In the prior examples showing font-level customisation (Figures 1 through 11), the microprinting consists mainly of rows of parallel lines, some of which contain repeated artwork that can be simulated at least in part using step-and-repeat processes. The next examples of artwork-level customisation are different because application of curvature and/or distortion affects characters differently depending on their location in a larger multiline microprinting pattern, which further prevents traditional counterfeiters from using step-and-repeat.

First, macro artwork patterns such as baseline curvature can be modified without also applying font-level customisation. For example, in Figures 12 and 13 each microprinted line is curved in a slightly different way than other lines, but apart from being rotated and placed on asymmetrically-curved baselines, characters from one part of the design look much like characters from other areas. A traditional counterfeiter might be able to replicate a single instance of each character and then copy and paste into multiple positions, but the rotation of each character or the curve of each different baseline would have to be replicated as well, so step-and-repeat would be difficult for entire lines. 

Figure 12: Offset microprinting incorporating a uniquely curved baseline for each line of text, including dynamic changes in vertical line spacing, but without changes to the font shape at the character level. One line differs from another mainly in character rotation, not in font shape.
Figure 13: Intaglio microprinting incorporating a uniquely curved baseline for each line of text, including dynamic changes in vertical line spacing but without changes to the font shape at the character level. One line differs from another mainly in character rotation, not in font shape.

Variable baseline curvature can also be combined with font-level customisations, such as bolding of text in certain areas as in Figure 14. For improved resistance to step-and-repeat counterfeiting, distortion to the font can be applied as a function of baseline curvature as illustrated in Figure 15, or a wave pattern like Figure 16, or any of a multitude of other patterns, one example of which is shown in Figure 17. In each case the distortion affects each character in the microprinting pattern slightly differently depending on its placement, resulting in a diversity of warped character shapes that forces traditional counterfeiters to treat every character as a unique element since characters cannot be repeated from one part of the artwork to another. 

Figure 14: Intaglio microprinting incorporating both font customisation (bold characters) and macro artwork level-customisation (dynamic curvature for each line).
Figure 15: Offset microprinting incorporating character distortion as a function of baseline curvature. A counterfeiter could not copy characters from one area and paste elsewhere, since the exact shape of each character depends on its position in the design.
Figure 16: Offset microprinting incorporating character distortion in a wave pattern. A counterfeiter could not copy characters from one area and paste elsewhere, since the exact shape of each character depends on its position in the design.
Figure 17: Offset microprinting incorporating character distortion. A counterfeiter could not copy characters from one area and paste elsewhere, since the exact shape of each character depends on its position in the design.

The general purpose of this strategy is to convert repeating text to non-repeating line art, but this could be done in many ways. For example, multiple font-level customisations could be combined with artwork-level customisations in ways not illustrated specifically in these examples. Taking a random hypothetical extreme case for purposes of illustration, consider a microprinting design containing various levels of bold and italicised characters in a custom font that is also distorted at a macro level. Such a microprinting design could still be assessed for readability but would be complicated for a traditional counterfeiter to redraw without knowledge of the specific steps the genuine designer followed to originate the design. 

Conclusion
As a second-level security feature, microprinting plays a specific security role and there are limits to what can be achieved by optimising it. However, microprinting is also among the most economical of security features and offers security designers considerable flexibility in combating not just digital counterfeiting, but also traditional counterfeiting. The microprinting artwork strategies discussed here are presented as a framework, and many novel combinations of these individual font and/or microprinting pattern customisation techniques can be combined with one another. Additionally, microprinting security can be about much more than artwork. Future work will review existing and introduce new design strategies related to microprinting ink colour (including multiplate offset and multicolour intaglio) and microprinting placement as it relates to user ergonomics and document alteration resistance. 

MORE ABOUT THE AUTHORS

Joel Zlotnick is employed by the US Department of State, Bureau of Consular Affairs, Counterfeit Deterrence Laboratory as a physical scientist. He conducts research on how design strategies can help maximise the security value of printing technologies and security features, and develops training programmes on counterfeit detection.

Tyra McConnell is a Forensic Document Examiner at the US Department of State, Bureau of Consular Affairs, Counterfeit Deterrence Laboratory. She provides training on security documents and develops presentations and e-learning courses regarding counterfeit detection.

Traci Moran is employed by the US Department of State, Bureau of Consular Affairs, Counterfeit Deterrence Laboratory as a physical scientist. She conducts research on security documents and delivers counterfeit detection training to varied audiences.

Disclaimer: This paper represents the opinions of its authors and not necessarily the opinions of the US government. The technologies and strategies described may not be available, appropriate or manufacturable for all document issuers. The examples shown do not imply anything about the quality of a document, its designer, its manufacturer, or the issuing authority. For informational purposes only.

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