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    Designing a secure banknote

    Kerre Corbin, Circulation, Authentication & Counterfeit Expert, De La Rue Currency

    The foundations of a secure banknote are strong security features that are well integrated into an engaging design and supported by public education. 

    The definition of a “strong security feature” is frequently debated, with suppliers and studies associated with suppliers leaning towards specific products or technologies. Perception studies can provide valuable insight into how a specific demographic interacts with banknotes or what they notice in a controlled experiment. But other factors also need to be considered when designing a secure banknote because the factors that combine to make a banknote secure are typically more subtle than often messaged. 
    Banknotes must meet the requirements of ALL users of the cash cycle, balancing aesthetics with security, functionality, capability to manufacture, machine readability, durability and cost. The security of a banknote is more than a single public recognition feature. Ultimately, the user considers the banknote holistically, which makes the design of the banknote incredibly important. There is a trend towards more security features per banknote – paper notes more frequently feature a thread and an applied feature than a decade ago and more modern polymer notes are more likely to have a security feature integrated into their window. With SAFEGUARD® ASSURE™ providing a covert feature in the very core of the polymer substrate both major banknote substrates can provide security features to meet every type of authentication need. Additionally polymer banknotes provide durable blind recognition features for central banks seeking to widen financial inclusion.
    Studies recommend taking advantage of the brain’s natural methods of visual analysis, i.e. to use the features of the banknote to guide looking and information  and the concept of a “navigation map” to link security features to graphic elements and encourage the public to visually travel across the banknote for ease of authentication.  A balance between features is important to ensure that one ‘stand-out’ feature does not mean the other important elements are ignored. It is also important to ensure that the visual images used in different features are different, to avoid re-use of a single image by counterfeiters.
    The responsibility of the design process is to bring all these together and engage people in their banknotes (whilst ensuring the banknotes are manufacturable and functional at every stage of their lifecycle). Aesthetics encourage people to look at a banknote for longer, with artistic elements capturing and holding attention long enough to engage with the different features. A feature that looks expensive and high impact will give users the belief that it is technically difficult to simulate, which provides reassurance. Such features require the appropriate secure effects and design to ensure the perception matches the reality. Additional processes such as overprinting and demetallisation can enhance the visual experience. It brings an overall coherence and visual journey to get interaction and provide users with an emotional reward. There is a reason that many people smile when they first see enhanced GEMINI™ magically appear under UV light.
    The format and layout are key in ensuring the denomination and main security features are noticed. This needs to be balanced with the technical and production rules to ensure that the note is engaging and effective. The effectiveness of a security feature depends heavily on its visual effects, but also on size, position and how feature integrates with the rest of the banknote’s design. Security features positioned too closely or to distantly from interesting design elements will not attract attention effectively.  Features positioned outside of the immediate gaze areas (e.g. in the corner, that can be covered by a finger) are unlikely to be seen. 
    The design needs to highlight the security feature and the easier it is to find and the more likely it is to be looked at directly. However, the increased saliency of one security feature may direct attention away from other security features, so this needs to be done with consideration for the overall visuals.

    “The best format, layout and design are intuitive and appear simple, whilst incorporating significant levels of complexity.”

    Different sizes for each denomination and different shape or image security features help protect against issues such as uprating or harvesting.  While banknote equipment manufacturers prefer to make every denomination very different to speed up banknote processing and improve accuracy, this goes against other studies which recommend designing a family of notes where features are similar for ease of identification and located in same position on each banknote.  It is important to ensure that while there may be design and location consistency in the security features to aid ease of visual focus no matter what the denomination, each denomination is unique with clear shapes and images related to that specific note.  This will limit confusion between denomination as well as raise the counterfeit challenge. 
    A secure banknote frequently combines public recognition features of different technologies with machine readable, teller and even covert features. Each technology or complex print feature represents a barrier to criminals attempting to counterfeit banknotes and the feel of the note is also recognised as playing a critical role. Good design then ensures that the banknote is not too complicated to look at. A balance can be achieved, using design to ensure that the public recognition and authentication features are prominent and striking whilst including the other elements that are needed in the note. While the user may not remember all features and design elements, the absence of them will be a trigger for an authentication response through other features.

    "The security features and design elements need to look as though they belong on the banknote – this is where good design plays a fundamental role."

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    There are multiple reasons for including different public features, not least that visual impairments affect a significant minority of the population. Some movement-based features only work with good stereo-vision but approximately 10-20% of adults lack the capability to perceive stereopsis (the ability to perceive the slight differences in perspective and location of the left and right hand view).  For this subset of the population 3D signals can never serve as sensory triggers, and they would have to rely on other sensory info such as patterns or colour – this means that 3D features are ineffective for some of the population. Similarly approximately 4.5% of the world population is colour blind.  Colour blind people may not be able to view certain colour switches within optically variable features.  This means that no one feature will work for everyone and a mix of options is required to cover all visual capabilities.

    "Visual impairments mean that no single public recognition feature will work for everyone."

     The requirement for layered security is important because banknote users consider the banknote holistically. Public education campaigns frequently suggest some type of variant of the Euro “look, feel, tilt” messaging. The extent to which people actively and fully do this is debatable. Studies suggest that people wont consciously examine individual security features to authenticate elements in isolation. The impact of a single feature is arguably much more important in the eyes of a security feature supplier than it is from those actively using the banknotes. Fortunately users look at the entire banknote holistically. During these interactions banknotes are naturally moved about whilst the ‘look’ and ‘feel’ elements act as a trigger that something isn’t quite right. This trigger is frequently a combination of multiple elements of the banknote that have not been perfectly replicated.
    Using technologies that have been pushed to their limit and combining with other features and processes makes convincing counterfeits much harder to produce. The risk of simulation is also important – every type of technology (micro-optics, holographics and colourshift) has been simulated and has decorative variants that are commercially available. Decorative variants are a world apart from the highly secure variants used for banknotes though. When highly secure technology variants combine with features that have a high level of design freedom (e.g. shape, size, colours and ability incorporate unique imagery) they are particularly effective: they widen the gap further between what is on a banknote and what is available commercially and they ensure that the feature can be well integrated into that banknote – the feature and the design looks like it belongs on the note meaning that any simulation is much more likely to trigger a user to realise if something is wrong.
    Overall designing a secure and engaging banknote requires expertise and the ability to consider the needs of the banknote from multiple different perspectives. Ensuring you have a secure banknote is much more nuanced than simply picking one single public recognition security feature.  

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