ISO/IEC 10118-1:2016

Overview

ISO/IEC 10118-1:2016 is the general part of the ISO/IEC 10118 series that defines the vocabulary, model and common requirements for cryptographic hash‑functions. The standard describes how hash‑functions map variable‑length bit strings to fixed‑length hash‑codes, explains fundamental properties such as collision resistance and preimage resistance, and sets out a general iterative model used by the specific hash algorithms published in later parts of the series.

Key topics and technical requirements

• Definitions and symbols: clear, standardized terminology (e.g., hash‑function, hash‑code, initializing value (IV), round‑function φ, output transformation T).
• Security properties: requirements for computational infeasibility of finding preimages or collisions (see Annex C for security considerations).
• General hashing model: a four‑step iterative process:
  1. Padding - pad input so length is a multiple of the block size L.
  2. Splitting - divide padded input into L‑bit blocks.
  3. Iteration - apply a round‑function φ iteratively with an initializing value IV to produce an intermediate state.
  4. Output transformation - apply T (e.g., truncation) to derive the final hash‑code.
• Padding methods: normative methods are specified (Method 1 - append ‘1’ then as many ‘0’ bits as needed; Method 2 - append length encoding with parameter r), and implementations must agree on which method is used.
• Parameterization: specification of L, IV, φ, padding, and T is required for any concrete hash‑function based on the model.
• Operational requirement: parties must operate on precisely the same bit representation of data prior to hashing to ensure interoperable results.
• Algorithm selection criteria: Annex B defines the criteria and process used to select candidate hash algorithms for inclusion in the ISO/IEC 10118 series.

Practical applications and users

ISO/IEC 10118-1:2016 is applicable wherever cryptographic hashing is required for:

• Authentication, message integrity and non‑repudiation (e.g., preparing digests for digital signatures).
• Commitment schemes where a user commits to a bit string without revealing it.
• Building Message Authentication Codes (MACs) when combined with secret keys (see ISO/IEC 9797‑2 for MAC construction using hash‑functions). Typical users:
• Security architects and cryptographers defining or validating hashing components
• Software and firmware engineers implementing cryptographic libraries
• Compliance officers, auditors and standards bodies assessing hash usage
• Device and application developers requiring interoperable, standards‑based hash implementations

Related standards

• ISO/IEC 10118 (other parts) - specific hash algorithms and detailed parameter sets
• ISO/IEC 9797‑2 - techniques for computing MACs using hash‑functions

Keywords: ISO/IEC 10118-1:2016, hash functions, collision-resistant, padding methods, round-function, hash-code, message integrity, non-repudiation, ISO/IEC 9797-2.