ISO/IEC 10118-3:2018

Overview

ISO/IEC 10118-3:2018 - IT Security techniques - Hash-functions - Part 3: Dedicated hash‑functions specifies a set of specially designed (dedicated) cryptographic hash‑functions. The standard defines these algorithms in detail: their models, parameters, byte ordering, padding methods, constants, initialization values and the iterative round‑function descriptions used to compute hash codes. Annex B provides numerical examples and Annex C includes SHA‑3 extendable‑output functions for information.

Key technical topics and requirements

• Models and design: Defines both a round‑function model (iterative construction) and a sponge model for dedicated hash‑function design and use.
• Algorithm specifications: Exact descriptions for multiple dedicated hash‑functions (e.g., RIPEMD‑160, RIPEMD‑128, SHA‑1, SHA‑224, SHA‑256, SHA‑384, SHA‑512, WHIRLPOOL, SHA‑512/224, etc.) including:
  • Parameters, functions and constants
  • Byte ordering conventions
  • Padding methods
  • Initializing values
  • Detailed round‑function operation and sequence
• Security guidance: Notes deprecation of Dedicated Hash‑Functions 1, 2 and 3 (RIPEMD‑160, RIPEMD‑128, SHA‑1 as listed) for new digital signature implementations due to short hash lengths and known cryptanalytic weaknesses. Their use remains allowed for legacy systems and for applications where collision resistance is not required (for example, certain MACs or KDFs per ISO/IEC 9797‑2 and ISO/IEC 11770‑6).
• Annexes: Numerical examples (Annex B) to aid implementers and SHA‑3 XOF information (Annex C).

Practical applications and who uses this standard

ISO/IEC 10118-3 is intended for:

• Cryptographic library implementers and software developers who need authoritative, interoperable definitions of hash algorithms.
• Security architects and protocol designers specifying hash functions for messaging, file integrity, key derivation or MAC constructions.
• Product vendors and embedded systems developers implementing legacy support or compliance with existing deployments.
• Evaluators, auditors and standards compliance officers verifying correct algorithm implementation and conformance.
• Educators and researchers referencing formal algorithm definitions and example vectors.

Use cases:

• Legacy system maintenance where older hash algorithms remain deployed.
• KDFs and MACs where collision resistance is not a primary requirement (per ISO/IEC 9797‑2, ISO/IEC 11770‑6).
• Implementations requiring exact algorithmic parameters, padding and byte‑order rules for interoperability.

Related standards

• ISO/IEC 10118‑1 (symbols and general provisions referenced)
• ISO/IEC 9797‑2 (message authentication codes)
• ISO/IEC 11770‑6 (key derivation)
• SHA‑3 specifications (referenced in Annex C for extendable‑output functions)

Keywords: ISO/IEC 10118-3, dedicated hash-functions, hash function standard, SHA-1 deprecation, RIPEMD, WHIRLPOOL, cryptographic hash, IT security techniques, collision resistance.