Glossary

A light-sensitive material used in processes such as photolithography and photoengraving to form a patterned coating on a surface. A substrate is coated with a light-sensitive organic material. A patterned mask is then applied to the surface to block light, so only unmasked areas are exposed. A solvent, called a developer, is then applied to the surface. In the case of a positive photoresist, the photo-sensitive material is degraded by light and the developer dissolves away exposed areas, leaving a coating where the mask was placed. In the case of a negative photoresist, the photo-sensitive material is strengthened (either polymerised or cross-linked) by light, and the developer dissolves away areas not exposed to light, leaving a coating in areas where the mask was not placed. This process is used to create surface grating images, which are the first stage in producing embossed holograms.

A device that utilises the unique, random, physical variations which occur naturally in a physical structure and which provide that structure with a ‘fingerprint’ that serves as a unique identifier. See also Fingerprinting – document.

A range of technologies whereby a material is released from a source and deposited on a substrate using a mechanical, electrochemical or thermodynamic process.

A process in which coin blank proofs are cleaned in acid to remove oil, directional rolling lines and dirt from their surface.

The illegal reproduction and distribution of copyright material, generally taken to be audio and video content.

In digital imaging, a pixel (or picture element) is the smallest item of information in an image. Pixels are arranged in a 2D grid, represented by squares. Each pixel is a sample of an original image, with more samples typically providing more accurate representations of the original.

A coloured or reflective disc containing a security feature and embedded in paper during manufacture.

Plasma is superheated matter – so hot that the electrons are ripped away from the atoms, forming an ionised gas. It comprises over 99% of the visible universe. In the night sky, plasma glows in the form of stars. That branch of lightning that cracks the sky is plasma. So is the sun… and so are neon signs on city streets. Plasma is often called ‘the fourth state of matter’, along with solids, liquids and gas. Just as a liquid will boil, changing into a gas when energy is added, heating a gas will form a plasma – a soup of positively charged particles (ions) and negatively charged particles (electrons).

In physics, a plasmon is a quantum of plasma oscillation. Just as light consists of photons, the plasma oscillation consists of plasmons. The plasmon can be considered as a quasiparticle since it arises from the quantisation of plasma oscillations,

The generation, detection, and manipulation of coherent electron oscillations (known as surface plasmon polaritons), as they travel together with an electromagnetic wave along the interface between a metal (eg. silver, gold) and a dielectric material (eg. glass, air) at the nanometric scale. Inspired by photonics, plasmonics follows the trend of miniaturising optical devices, and can be applied as a security feature. The plasmons can be controlled through careful modelling and application of, among other things, the dielectric and metal layer thickness in a ‘sandwich’ structure. When the sandwich structure is applied as a device to a security document, it allows light that falls on the surface of the device to be controlled in terms of its wavelength (allowing control over the colour) and amplitude (giving rise to the intensity, or brightness of the colour generated).

A model made during the coin design process, approximately four times larger than the actual size of the final coin or medal.

A device allowing the use of payment cards at a physical (not virtual) point of sale. The payment information is captured either manually on paper vouchers or by electronic means.

The alignment of the electric and magnetic fields in a particular orientation in a lightwave. If all the waves in a beam of light move up and down or from side to side together, the beam is said to be plane-polarised. Some materials have the ability to filter out all lightwaves except those in a particular direction. Other materials are said to be optically active if they are able to change the angle of a plane-polarised beam of light. Liquid crystals often have this property and this enables them to be detected.

An optical device which transforms unpolarised light into polarised light. It is used to examine light reflected from ink or thin-film coating. It blocks light rays of a specific polarisation direction while letting light rays of other polarisation directions pass.

An increasingly popular thermoplastic polymer used as the substrate of choice for ID cards and the data pages of passports, due to its durability, high dimensional stability and transparency. It also lends itself to laser engraving and ablation for additional security features.

A thermoplastic polymer resin of the polyester family, used to make the most common container in the soft drink market today: the plastic bottle. Also used as the base material for most surface-applied holograms and security threads.

A substance or material consisting of very large molecules, or macromolecules, composed of many repeating subunits. Plastic and polyester are all polymers. Polymer banknotes were first introduced in Australia and are widely used around the world.

A laboratory technique for rapidly producing (amplifying) millions to billions of copies of a specific segment of DNA, which can then be studied in greater detail.

The act of converting a paper banknote design for use with polymer substrate.

A thermoplastic polymer used as a substrate in many documents. However, polycarbonate is often preferred as a substrate for security printing and documents requiring high durability.

A stacked linear barcode format used in a variety of applications such as transport, identification cards, and inventory management. The ‘417’ signifies that each pattern in the code consists of 4 bars and spaces in a pattern that is 17 units (modules) long.

The holding of banknotes/CBDCs as a store of value, for saving purposes or as a precaution for uncertainties.

Preparatory work required on original materials, such as films, files and plates to carry out the printing of a banknote or other security document.

A label construction made up of three layers: a face material, a pressure-sensitive adhesive, and a backing sheet coated with a release agent. Pressure-sensitive labels only need the pressure of a hand to be applied to an item.

In colour printing, print registration is the layering of printed patterns to form a multicolour image. Registration error refers to position misalignment in overlapped patterns, resulting in printed colours in the wrong areas, overprint or white space.

A plant for producing banknotes and other security documents. Printworks can be either state or central bank-owned or run by commercial companies.

The overprinting of two or more coloured inks to create a blended colour affect that is difficult to match on copiers. Prismatic colour blending is visually similar to split fountain printing, but differences become apparent when the images are magnified.

Private DLTs are open to participants approved by a central authority with control over the DLT network and its design. Information regarding the private DLT is not usually available outside the network.

A secret key that must only remain known to the recipient. A private key is somewhat comparable to a pin or verification code.

Money held in the form of deposits and used for lending by a commercial bank.

An automated system installed on product manufacturing lines, using sensors and scanners to provide tax authorities and other government agencies with full visibility on what is being produced and ensure that every production unit has been affixed with a valid unique identifier, tax stamp, or secure label.

The ability to apply a coded instruction automatically to a digital payment so that if set conditions are met, an action then happens. It is most often the payment that is programmable and not the money used to make that payment, but the distinction between the two is still being sorted out. See also Smart contract.

A carefully struck coin using special dies, with frosted images on a mirror-like background. Proof refers to a method of manufacture, not a condition or grade.

In cryptocurrency, proof of stake uses a deterministic algorithm based on the number of coins owned by a user. This algorithm offers the possibility for nodes to increase their chances of being elected to mine more coins and encourages coin owners to maintain the network because the choice is random. The more coins owned, the higher the chance of being chosen. See also Proof of work.

In cryptocurrency, proof of work solutions refer to transactions secured through a linear trail of transaction history and the use of a computational puzzle (‘proof of work’ consensus algorithm) which reflects that work.

A protocol for verifying cryptocurrency transactions. Nodes use their computing power to prove themselves sufficiently trustworthy to be allowed to add new information about transactions to the network.

A set of policies, processes, server platforms, software, and workstations used for administering public key certificates and public-private key pairs, including the ability to issue, maintain, and revoke certificates.

Money that is issued and held by a central bank.

A cooperative arrangement between two or more public (ie. government) and private sector entities.

A multilingual site with information on authentic identity and travel documents in the EU. Document descriptions include technical descriptions of some of the most important security features on the document. Document experts in all EU member states as well as Iceland, Norway and Switzerland provide and select the information to be released to the general public via PRADO.

A fibrous material produced by mechanically or chemically reducing plants to their component parts from which pulp, paper and paperboard sheets are formed after proper slushing treatment.

A computer that uses specialised technology – including computer hardware and algorithms that take advantage of quantum mechanics – to solve complex problems that classical computers can’t solve, or can’t solve quickly enough.

Semiconductor particles a few nanometres in size with optical and electronic properties that differ from larger particles due to quantum mechanics. Quantum dots may be ‘tuned’ to provide specific visual effects.

A fundamental theory in physics that describes the behaviour of nature at and below the scale of atoms. It is the foundation of all quantum physics.

The basic unit of information used to encode data in quantum computing. Can be best understood as the quantum equivalent of the traditional bit used by classical computers to encode information in binary.

A type of 2D matrix barcode which stores information as a series of pixels in a square-shaped grid. Typically, smartphones are used to scan QR codes, displaying an image of the code and converting it to, say, a standard URL for a website. QR codes can store up to 4,296 alphanumeric or 7,089 numeric characters and are clearly distinguished from datamatrix barcodes by large squares placed at three corners of the code, which are used for alignment. Compared to standard UPC barcodes, QR codes offer faster reading of the optical image and greater data storage capacity in applications such as product tracking and item identification.

An act of cybersecurity fraud using QR codes to redirect victims to malicious websites or prompt them to download harmful content. The goal of this fraud is to steal sensitive information, such as passwords, financial data, or personally identifiable information, and use that information for other purposes, such as identity theft, financial fraud, or ransomware.

A wireless, non contact technology that uses radio waves to transfer data and passively identify a tagged object. RFID systems are usually comprised of an RFID reader, microchip tags, and antennas. The reader gives off radio waves and gets signals back from the tag, while the tag uses radio waves to communicate its identity and other information. The tags are now so small that they can be neatly implanted into paper. They can typically be detected at distances ranging from a few millimetres to several metres. RFID is used in various commercial and industrial applications, including tracking items along a supply chain.

A rainbow is the visual result of splitting white light into its constituent colours according to wavelength. The order of the colours is red, orange, yellow, green, blue, indigo, violet – with red having the longest wavelength and violet the shortest. The natural phenomenon is caused by the prismatic effect of raindrops in the sky but it can also be caused by diffractive gratings with a spatial frequency approaching the wavelength of light.

When illuminated with incandescent (white) light, rainbow holograms display images bathed in a changing rainbow spectrum of colours as the viewer moves their eyes up and down. Holographers have developed considerable control over the colours displayed in this type of hologram to produce images in a specific colour or in near natural colour.