ISO/IEC 39794-2:2023

Overview

ISO/IEC 39794-2:2023 defines an extensible, interoperable data interchange format specifically for finger minutiae (fingerprint minutiae) data. It standardizes how minutiae (ridge endings, bifurcations, cores, deltas and related attributes) are represented, encoded and exchanged between biometric systems. The standard provides both a tagged binary format (ASN.1 / DER-style TLV) and a textual XML encoding capable of holding the same information, plus an on‑card biometric comparison format optimized for smartcards and secure elements.

Note: ISO/IEC 39794-2 covers only finger minutiae - it is not applicable to palms, toes or feet (see ISO/IEC 39794-4 for image data across fingers, palms, toes and feet).

Key topics and technical requirements

• Extensible encodings
  • Tagged binary encoding based on ASN.1 and TLV semantics for compact interchange.
  • XML Schema Definition (XSD) for textual interchange and human readability.
  • On‑card biometric comparison format encoded with extensible TLV for secure, constrained environments.
• Minutiae representation
  • Specifications for minutia location, direction/angle, type (ridge ending, bifurcation, unique minutia, trifurcation encoding) and placement conventions (core/delta placement).
  • Coordinate systems and conventions to ensure consistent interpretation across devices.
• Supporting data elements
  • Capture metadata (device model, capture date/time, spatial sampling rate, impression type).
  • Quality blocks, zonal quality, ridge counts (generic, 4-neighbour, 8-neighbour), PAD (presentation attack detection) data, and vendor‑specific blocks.
• On‑card matching parameters
  • Parameters and rules for constructing valid probe data and performing biometric comparison on smartcards or secure elements.
• Conformance
  • Normative conformance assertions, conformance test procedures, and encoding examples (annexes provide formal specs, test methodology and examples).

Practical applications and users

• Who uses it
  • Biometric middleware and system integrators, fingerprint sensor and device manufacturers, smartcard and secure element developers, law enforcement and forensic labs, border control and government identity programs, and vendors implementing on-card matching.
• Why it’s used
  • Enables interoperability between different vendors and devices.
  • Provides extensibility so new attributes can be added without breaking compatibility.
  • Supports compact binary exchange, readable XML, and secure on‑card matching workflows.
  • Facilitates standardized quality metrics and conformance testing for reliable deployments.

Related standards

• ISO/IEC 39794 (series) - third-generation extensible biometric interchange formats.
• ISO/IEC 39794-4 - finger, palm, toe and foot image data (complements minutiae-focused Part 2).
• Legacy references: ISO/IEC 19794-2 (earlier fingerprint minutiae standards; retained in catalogues).

Keywords: ISO/IEC 39794-2, finger minutiae, fingerprint minutiae data, biometric data interchange, ASN.1, XML schema, on-card biometric comparison, TLV, biometric interoperability, conformance testing.