ISO/IEC 18033-1:2021

Overview

ISO/IEC 18033-1:2021 - Information security - Encryption algorithms - Part 1: General - is the general, definitional part of the ISO/IEC 18033 series. Published in 2021 (third edition), it establishes the foundational terminology, concepts and high-level considerations that apply across the series. The standard introduces the nature and purpose of encryption, distinguishes symmetric and asymmetric systems, and describes general aspects of use, key management and security properties.

Key topics and requirements

• Terms and definitions: authoritative definitions for core concepts such as encryption, decryption, plaintext, ciphertext, key, public/private key, block cipher, stream cipher, homomorphic encryption, identity‑based encryption, attack and related metrics.
• Nature of encryption: objectives of confidentiality and the relationship between encryption and decryption algorithms.
• Symmetric vs. asymmetric systems: high-level distinctions and assumptions (e.g., key pairs for asymmetric systems).
• Key management: general considerations for keys used by encryption systems.
• Use and security properties: discussion of general properties for different classes of ciphers, including:
  • Block ciphers (and modes of operation, MACs)
  • Stream ciphers and keystream properties
  • Asymmetric and identity‑based encryption systems
  • Homomorphic encryption and its defining property
• Attacks and evaluation: annex on attacks (Annex C) and metrics like attack cost.
• Submission and deletion criteria: informative annexes (A and B) define criteria for adding or removing encryption systems from the ISO/IEC 18033 series.
• Object identifiers and normative references: guidance for identifiers and pointer to Parts 2–7 for algorithm‑specific standards.

Practical applications and who uses it

ISO/IEC 18033-1:2021 is used by:

• Cryptographers and algorithm designers - to ensure consistent terminology and to understand evaluation criteria and attack models.
• Security architects and engineers - for selecting appropriate encryption classes (block/stream/asymmetric/homomorphic) and understanding general properties and key management implications.
• Product developers and vendors - to align implementations with recognized terminology and interoperability expectations across the ISO/IEC 18033 series.
• Standards bodies, evaluators and procurement teams - to apply submission/deletion criteria when assessing or specifying encryption algorithms and to reference a common vocabulary in specifications and procurements.

Practical uses include documentation of cryptographic requirements, interoperability planning, threat modeling (using the attack guidance), and scoping more detailed algorithm standards in Parts 2–7.

Related standards

Normative references in this part point to the rest of the series:

• ISO/IEC 18033-2 (Asymmetric ciphers)
• ISO/IEC 18033-3 (Block ciphers)
• ISO/IEC 18033-4 (Stream ciphers)
• ISO/IEC 18033-5 (Identity-based ciphers)
• ISO/IEC 18033-6 (Homomorphic encryption)
• ISO/IEC 18033-7 (Tweakable block ciphers)

Keywords: ISO/IEC 18033-1:2021, encryption algorithms, information security, block ciphers, stream ciphers, asymmetric encryption, homomorphic encryption, identity-based encryption, key management, cryptographic standards.