Mythos Hardening Control · MRIS 2.0 · Applies to ISO/IEC 27001 and IT-Grundschutz

MHC-01 Post-quantum strategy and cryptographic inventory

Protects long-lived confidential data captured today from later decryption (“harvest now, decrypt later”) and, with the cryptographic inventory, lays the groundwork for an orderly migration to post-quantum algorithms.

At a glance

Operational benefit: protects long-lived confidential data against the "harvest now, decrypt later" pattern and creates the ability to exchange cryptographic methods swiftly when required.
Policy affected: cryptography policy (encryption and key management).
Dependencies: no precondition; presupposes an understanding of the encryption in use (inventory).
Effort drivers: depends on the number of systems and data flows using encryption and on the exchangeability of the libraries used. The actual effort depends on the organization's resources.
Primary metric: share of the cryptographic methods in use that are recorded in the central inventory and classified by migration priority.
Standards touched (no claim of fulfilment): ISO/IEC 27002 A.8.24; NIST FIPS 203/204/205; BSI TR-02102; C5:2026 CRY-01; EU recommendation on PQC migration.

Control statement

The organization maintains an inventory of all cryptographic methods in use and pursues a documented strategy for migrating to quantum-safe methods in good time. During the transition, hybrid methods are used.

Purpose and threat relevance

Future quantum computers will be able to break encryption that is widespread today (such as RSA and elliptic curves). Attackers are therefore already intercepting encrypted data now in order to decrypt it later — the "harvest now, decrypt later" pattern. Data that must remain confidential over many years is particularly affected. AI additionally accelerates the discovery and exploitation of weak or outdated crypto implementations. The harvesting pattern concerns not only encrypted data but also signatures valid today: certificates, code signatures and long-lived signed documents can be harvested and later retroactively forged or repudiated, once a sufficiently powerful quantum computer becomes available. During migration there is a further risk that a hybrid connection is forced back by an attacker onto its purely classical component and thereby loses its quantum safety. The protective objective is to migrate long-lived confidential data to quantum-safe methods in good time and to create the ability to change methods swiftly when required.

Effect across frameworks

These are the controls and requirements the MHC acts on. The classification shows how much each control loses its effect under AI-enabled attacks.

Effect across frameworks
Number	Title	Classification / Level
ISO/IEC 27001:2022, Annex A 1 controls
A.8.24	Use of cryptography	robust
IT-Grundschutz, MRIS.bd 1 requirements
MRIS.bd.1.A5	Creating a Cryptographic Inventory and a Post-Quantum Migration Strategy	Basic

All 93 controls in the analysis matrix · All 23 requirements of the module family

Maturity path

Initial: cryptographic inventory documented.
Defined: migration strategy adopted; hybrid methods piloted in one area.
Managed: hybrid or quantum-safe methods in production use; annual review automated.

Measurement and audit evidence

Metric: share of the methods in use that are recorded in the inventory and classified by migration priority (target: complete coverage of the areas requiring protection).
Evidence: crypto inventory, migration strategy with triggers and schedule, pilot and production evidence for hybrid methods.
Evidence logic (following ISO/IEC 27001, Clause 9): documented? — inventory and strategy; responsible? — the named function; frequency? — annual or event-driven review; tolerance? — no long-lived confidential data without a migration plan.

Typical mistakes

A strategy is formulated without a complete inventory being available — the most important points remain unknown.
Hybrid methods are introduced across the board without prioritizing by confidentiality period — much effort without a recognizable focus of benefit.
Encryption is hard-wired into the code, so that a later change of method requires intervention in the application each time.
Migration is treated purely as a topic for the future, even though today's data outflow already determines tomorrow's risk.
PQC is introduced at derived levels while the root of the key hierarchy (master key, root CA) remains classical — the unprotected trust anchor renders the measures below it ineffective.

Delimitation and residual risk

Delimitation: concerns the cryptography in use, including the PQC-specific migration order within the key hierarchy and the downgrade resistance of hybrid negotiation; routine key management (generation, rotation, storage) remains part of general cryptography practice (A.8.24).
Residual risk: as long as classical methods run in parallel, the risk remains that data already exfiltrated will later be decrypted; quantum-safe methods are moreover comparatively young and continue to be monitored.
ISO/IEC 27002:2022: A.8.24 Use of cryptography.
Framework: NIST FIPS 203 (ML-KEM), FIPS 204 (ML-DSA), FIPS 205 (SLH-DSA); NIST SP 1800-38 (migration guide, NCCoE); BSI TR-02102; C5:2026 CRY-01; EU recommendation on coordinated PQC migration.
Further reading on key management: Cloud Security Alliance, Cloud Key Management Working Group – Post-Quantum Cryptography Key Management (draft, August 2026).

Implementation in detail

Organizational and technical implementation, implementation examples and the prioritization within the overall programme are described in the Implementation Guide.

Implementation Guide (PDF)Back to the MHC catalog