ISO/IEC 29192-5:2016

Overview - ISO/IEC 29192-5:2016 (Lightweight hash-functions)

ISO/IEC 29192-5:2016 specifies three standardized lightweight hash-functions designed for constrained environments (low-power, low-area or low-memory devices). The standard is part of the ISO/IEC 29192 family for lightweight cryptography and defines algorithms and operational details suitable for efficient hardware and software implementations.

Standardized algorithms:

• PHOTON - five variants (permutation sizes: 100, 144, 196, 256, 288 bits) producing hash-codes of 80, 128, 160, 224, 256 bits respectively. PHOTON reuses small S-box components (PRESENT/AES style) and provides documented preimage/second-preimage/collision resistances for each variant.
• SPONGENT - five variants (permutation sizes: 88, 136, 176, 240, 272 bits) producing hash-codes of 88, 128, 160, 224, 256 bits respectively; optimized for hardware sponge constructions.
• Lesamnta-LW - a software-oriented hash-function with a 384-bit internal permutation delivering a 256-bit hash-code, based on a compression function and block-cipher primitive.

Key technical topics and requirements

• Target environments: constrained devices such as IoT nodes, RFID, smartcards, and embedded sensors that need small area, low power and limited memory.
• Permutation-based designs: each function is specified by internal permutations, domain extension (sponge or compression-based), and padding rules.
• Security properties: the standard documents collision, preimage and second-preimage resistance levels (explicitly for PHOTON variants); note that some PHOTON variants (PHOTON‑100 and PHOTON‑144) do not meet the minimum collision/second-preimage strengths required by ISO/IEC 29192‑1 and have constrained use-cases.
• Implementation focus: PHOTON and SPONGENT are optimized for hardware; Lesamnta-LW is optimized for software implementations.
• Normative references: ISO/IEC 29192‑1 defines the overall lightweight cryptography requirements referenced by this part.

Practical applications - who uses ISO/IEC 29192‑5

• Embedded and IoT product developers that require standardized, lightweight hash-functions for integrity checks, device authentication primitives and compact digests.
• Security architects and firmware engineers designing cryptographic protocols for constrained platforms.
• Hardware designers and ASIC/FPGA implementers seeking compact, low-cost hash primitives.
• Standards bodies and procurement teams specifying compliant lightweight cryptography for constrained-device ecosystems.

Typical uses include firmware integrity checks, compact message digests for constrained communications, and building blocks for lightweight authentication and key-derivation schemes where resource efficiency is critical.

Related standards

• ISO/IEC 29192‑1: General requirements for lightweight cryptography (normative).
• Other parts of ISO/IEC 29192 cover block ciphers (Part 2), stream ciphers (Part 3) and asymmetric mechanisms (Part 4), which complement the hash-function options defined in Part 5.

Keywords: ISO/IEC 29192-5:2016, lightweight cryptography, PHOTON, SPONGENT, Lesamnta-LW, hash-functions, constrained devices, IoT security, sponge function, permutation-based hash.