Overview
ISO/IEC 19592-2:2017 - Information technology - Security techniques - Secret sharing - Part 2: Fundamental mechanisms specifies cryptographic secret sharing schemes and their core mechanisms. The document standardizes how a secret (message) is split into shares (message sharing algorithm) and how it is recovered from shares (message reconstruction algorithm). It covers multiple schemes, their parameters, algorithms, properties, and supporting material such as object identifiers and numerical examples.
Key topics and requirements
- Fundamental functions: clear specification of the two primary functions - sharing (split secret into shares) and reconstruction (recover secret from shares).
- Scheme parameters: explicit definitions for message space, share space, number of shares (n), and reconstruction policy (threshold, access structure, or adversary structure).
- Shamir secret sharing: parameterization over a finite field K, use of fixed field elements for share indices, random polynomial coefficients, and reconstruction from any k shares.
- Ramp Shamir scheme: a variant that trades perfect secrecy for smaller share sizes; parameters and reconstruction thresholds are defined.
- Additive secret sharing families:
- General additive secret sharing for arbitrary adversary structures.
- Replicated additive secret sharing.
- Computational additive secret sharing, including a conversion protocol for translating shares between schemes.
- Mathematical foundations and primitives: use of finite fields, cyclic/abelian groups, polynomials, and deterministic random bit generators (DRBGs) where needed.
- Auxiliary content: Annex A lists object identifiers (OIDs) for mechanisms; Annex B gives informative numerical examples illustrating schemes and algorithms.
- Interoperability & properties: definitions conformant with ISO/IEC 19592‑1:2016 (Part 1), with emphasis on confidentiality and recoverability. (Note: verifiability is not provided by the schemes in this part.)
Practical applications and users
ISO/IEC 19592-2 is intended for implementers and architects who need standardized secret sharing building blocks:
- Security engineers & cryptographers implementing threshold systems and secret-splitting primitives.
- Developers of secure multi‑party computation (MPC), distributed key management, and threshold cryptography.
- Cloud providers and system architects designing resilient secret storage, backups, or distributed key custody.
- Standards bodies, auditors, and compliance teams seeking consistent definitions and object identifiers for interoperability.
Typical use cases:
- Securely distributing cryptographic keys across multiple custodians.
- Storing confidential values redundantly with provable recoverability.
- Enabling MPC protocols that require share-based input protections.
- Converting shares between schemes to meet changing threat or performance requirements.
Related standards
- ISO/IEC 19592-1:2016 - General definitions and terminology for secret sharing (normative reference for Part 2).