ISO/IEC 29192-2:2019

Overview

ISO/IEC 29192-2:2019 - "Information security - Lightweight cryptography - Part 2: Block ciphers" specifies three lightweight block ciphers intended for constrained environments. The standard standardizes algorithms, notation and implementation details for:

• PRESENT - 64-bit block cipher (key: 80 or 128 bits)
• CLEFIA - 128-bit block cipher (key: 128, 192 or 256 bits)
• LEA - 128-bit block cipher (key: 128, 192 or 256 bits)

The document includes algorithm pseudocode, transformations (S-boxes, permutations), key schedules, numerical examples, object identifiers and feature tables to support interoperable, lightweight cryptographic implementations.

Key topics and technical requirements

• Algorithm specifications: Full encryption and decryption procedures for PRESENT, CLEFIA and LEA, with explicit round structures and internal state representation.
• Block and key sizes: Clear definition of supported block sizes (64-bit for PRESENT, 128-bit for CLEFIA/LEA) and approved key lengths.
• Round functions and building blocks: Descriptions of S-box layers, permutation layers (e.g., PRESENT pLayer), inverse transformations and round key derivation (key schedules).
• Implementation guidance: Pseudocode, numerical examples (Annex B), feature tables (Annex C) and limitations (Annex D) that help developers assess security bounds and performance trade-offs.
• Object identifiers: Normative Annex A defines OIDs for algorithm identification in protocols and certificates.
• Legal/patent notice: ISO/IEC notes potential patent claims and advises implementers to review patent declarations and licensing terms.

Practical applications

ISO/IEC 29192-2 targets use where low-resource or low-power cryptography is essential:

• IoT devices and sensor nodes (battery-powered, low-memory)
• Embedded systems and microcontrollers with constrained CPU cycles and RAM
• RFID, smart cards and wearables requiring small-code-footprint ciphers
• Industrial control and automotive ECUs where cryptographic overhead must be minimized
• Protocol designers and implementers who need standardized lightweight block ciphers for secure messaging and data protection

Adopting these standardized algorithms helps ensure interoperability, reproducible implementations and easier security assessments for constrained devices.

Who should use this standard

• Firmware and embedded systems developers
• Security architects for IoT and low-power products
• Cryptographers and implementers validating compliance
• Certification bodies and product evaluators
• Standards and protocol designers seeking lightweight cipher options

Related standards

• ISO/IEC 29192-1 - Lightweight cryptography: requirements and general guidance (see ISO website for the complete 29192 series).
• Consult the ISO/IEC patent database and national standards bodies for licensing and implementation guidance.

Keywords: ISO/IEC 29192-2, lightweight cryptography, block ciphers, PRESENT, CLEFIA, LEA, IoT security, embedded encryption, constrained environments.