Banknote security comes at a price commercial packaging can rarely afford

1. Serialisation and variable security barcodes

• Frequency: Very high / Industry standard
• Application: Unique identifiability forms the basis for seamless traceability and logistics security. Complex 2D codes are used in particular for packaging requiring protection in the pharmaceutical sector in accordance with the EU Falsified Medicines Directive (FMD), or for the labelling of luxury goods with tamper-proof labels. Formats such as DataMatrix or QR codes encrypt large amounts of data in a minimal space in a tamper-proof manner.
• Implementation & cost-effectiveness: Inexpensive to moderately priced (digital printing). As the code must vary from one package to the next, this technology is the domain of digital printing using high-speed inkjet, as well as toner and laser printing systems. In this process, they often print only the code and other variable features, whilst the majority of the product has already been produced beforehand using a different printing process.
• Challenge: The bottleneck is not the actual printing process, but real-time quality control at extreme production speeds. Every single pixel pattern must be captured inline by a camera system, decoded and evaluated in accordance with ISO/IEC standards (such as ISO/IEC 15415). Illegible codes or duplicates are automatically sorted out before they compromise the entire track-and-trace system. Some methods aim to make physical code structures and paper textures directly verifiable by consumers using a smartphone camera.

2. Special inks (UV fluorescence, infrared and magnetic inks)

• Frequency: High / Widespread
• Application: These physically and chemically modified formulations form the backbone of automated authenticity checks in sorting facilities, at customs checks or at cash machines.
  • UV-fluorescent inks use organic or inorganic pigments that absorb invisible UV light and glow in the visible spectrum. Dual-wavelength inks are particularly sophisticated, emitting a different colour (e.g. red) under 365 nm UV light than under short-wavelength 254 nm UV light (e.g. green).
  • Infrared and anti-Stokes (upconversion) inks absorb IR light or, through highly complex crystal structures, emit higher-energy visible light when irradiated with low-energy infrared (at around 980 nm).
  • Magnetic inks (MICR) contain ferromagnetic pigments and are used for the rapid reading of banknotes and cheques.
• Implementation & cost-effectiveness: Moderate (analogue and digital printing). Speciality inks can be easily integrated into existing analogue production systems for flexographic, offset or screen printing. This keeps variable unit costs low for medium and large print runs. Digital inkjet printing is also gaining in importance in this area.
• Challenge: The particle size and density of these special pigments significantly alter the flow properties (rheology) of the ink. In analogue printing processes, this leads to increased abrasiveness and rapid wear of tools and plates (particularly with MICR inks). In digital inkjet printing, the large pigments threaten to block the fine nozzles (nozzle clogging), which requires complex dispersion techniques. In the case of UV-curing fluorescent inks, the absorbent pigments also compete with the photoinitiators for the UV light from the curing lamps. For use in pharmaceutical, cosmetic or food packaging, EuPIA-compliant, low-migration formulations are required, which must also be recyclable.

3. Microtext and guilloche patterns

• Frequency: Medium
• Application: Guilloches are precise, mathematically calculated and interlaced line patterns. In combination with microtext (character heights below 0.2 mm, which appear to the naked eye as a simple line), they offer effective protection against attempts at copying. As digital CCD and CMOS image sensors in standard scanners reach their resolution limits, the continuous line pattern breaks up into a dot matrix during digitisation. This produces characteristic moiré and superimposition effects.
• Implementation & cost-effectiveness: Moderate to complex (high-resolution offset printing or precision inkjet). Whilst banknotes are produced using the extremely expensive intaglio printing process – in which viscous ink is pressed from steel plates into cotton paper under pressures exceeding 80 tonnes to create a tactile relief – the commercial sector typically relies on high-performance offset printing presses or digital printing solutions with a resolution of at least 1200 dpi for securities, certificates or forgery-proof labels, the commercial sector usually relies on high-performance offset printing presses or digital printing solutions with a resolution of at least 1200 dpi.
• Challenge: The critical factor is physical dot gain. As liquid ink spreads capillarily along the paper fibres after being applied, there is a risk that the finest lines and text will run and merge before the ink has completely dried. This requires precise control of the surface tension of the substrate, precisely coordinated drying speeds and high registration accuracy for multi-colour linework.

4. Optically variable devices (OVDs) and holograms

• Frequency: Rare
• Application: Kinegrams, satellite holograms or optically variable effects change their motif or colour depending on the angle of illumination and viewing angle. They serve as an intuitive authenticity feature for consumers, verifiable without the need for special tools, for high-quality documents ranging from prestigious, forgery-proof business cards in the premium segment to passports, cosmetics and branded packaging.
• Implementation & cost-effectiveness: Complex and expensive (hot/cold foil stamping or digital embellishment). The physical master for high-security OVDs is produced using electron beam lithography (E-beam lithography): Nanometre-scale diffractive gratings (0.5 to 30 micrometres deep) are written into photoresist and electroformed into embossing dies (nickel shims). In commercial mass production, these foils are applied using hot or cold foil transfer systems. For short runs or personalised finishes, digital varnishing and foiling (digital embellishment) is becoming the norm.
• Challenge: Analogue embossing processes involve enormous mechanical set-up times and tooling costs for engraved metal cylinders. Digital finishing systems apply UV varnishes tool-free via piezoelectric nozzles. The greatest physical hurdle lies in three-dimensional flow control: to achieve a perceptible relief effect, varying varnish layers ranging from 21 µm to 116 µm must be built up with sharp edges in a single pass.

5. Forensic markers (DNA biomarkers & tagging)

• Frequency: Very rare / Exotic
• Application: These Level 3 features serve as irrefutable evidence in court. Invisible molecular marking systems are mixed directly into carrier coatings, printing inks or paper substrates in minute concentrations (in the ppm or ppb range) to secure high-quality packaging or sensitive documents in the premium sector.
  • Botanical, synthetic DNA (such as SigNature DNA) encodes forgery-proof genetic information.
  • Dual-Colour Centre Diamonds are microscopic synthetic diamond particles with targeted lattice defects (germanium and silicon vacancies). When excited by a 532-nm laser, they emit specific, physically distinct optical signals (Raman scattering, zero-phonon lines), which generate an unclonable signature with high information density.
• Implementation & Cost-Effectiveness: Extremely labour-intensive and very costly. Verification is not possible inline during the production process and requires time-consuming laboratory analyses (PCR tests) or specialised portable Raman spectrometers. Quality control is therefore carried out on a random sampling basis after production.
• Challenge: The greatest hurdle is the physical survivability of the markers during the printing process. The production of high-viscosity offset or security printing inks requires mechanically aggressive dispersion processes (such as on a three-roll mill). The hydrodynamic shear forces generated during this process can mechanically tear the sensitive, long-chain DNA molecules apart, thereby destroying their coding sequence. Furthermore, the markers must be resistant to aggressive chemical solvents and reactive monomers in UV inks.

Digital product passports and physical fingerprints

However, the era of isolated, passive security features is drawing to a close. Driven by the European Ecodesign Regulation (ESPR), the Digital Product Passport (DPP) will gradually become mandatory from 2026/2027. This will apply to batteries from 2027 and to textiles from 2028, where extremely durable, washable RFID yarns (such as e-Thread yarn) are sewn directly into the fabric as indestructible product IDs to bridge the gap to the digital product file.

Whilst the national Packaging Act (including the PPWR requirements) primarily regulates material cycles and recyclability, the Digital Product Passport (DPP) bridges the gap to the digital product file. However, as printed QR codes alone can be easily copied, so-called Physical Unclonable Functions (PUFs) are taking centre stage in research. This technology turns the physical randomness of the substrate into a forgery-proof security feature. In the case of a paper-fibre PUF, the unique, unclonable fibre pattern of a sheet of paper is scanned by a smartphone immediately after printing and stored as a cryptographic hash value in a decentralised database (such as a blockchain). Bionic optical signatures, material-specific texture fingerprints (paper/porcelain fingerprinting) or time-resolved physical PUFs (Time-Dependent PUFs), whose optical emission from triplet excitons decays dynamically over time, make forgery physically impossible.

Regulated by global industry standards such as ISO 14298 for the management of physical security printing processes and ISO 22381 for IT interoperability, physical material excellence and digital cryptography merge to form a networked, forgery-proof security ecosystem of the future.