Construction Framework & Migration Paths

A blueprint for building post-quantum cryptographic security capability, synthesized from the China-based industry report 安全牛《后量子密码安全能力构建技术指南（2025版）》. It frames the work under the guiding principle of proactive defense, steady migration, and self-controllable (积极防御、稳步迁移、自主可控): start early, move without breaking production, and retain sovereign control over the algorithms and implementations you depend on.

The security-capability architecture

The report organizes PQC capability building around a security architecture with four interlocking core elements. Each one is a workstream that must advance for the others to deliver value — upgrading algorithms in application code, for example, is wasted if the PKI that issues certificates still speaks only RSA and ECC.

Five design principles

The report sets out five principles that should govern every architectural decision in the program:

1. Minimal change — prefer drop-in upgrades over re-architecture; touch as little of the surrounding system as possible.
2. Algorithm agility (crypto-agility) — abstract the algorithm behind a stable interface so it can be swapped again as standards evolve. See crypto-agility.
3. Performance optimization — exploit hardware acceleration and parallelism to absorb the larger keys and heavier operations of PQC.
4. Interoperability — follow both domestic and international standards so deployments interwork across vendors and borders.
5. Self-controllable (自主可控) — favor implementations and supply chains the organization can audit and sustain independently.

Three migration paths

The report describes three migration paths. They are not mutually exclusive — a large estate typically uses all three across different systems — but each has a distinct profile of effort, risk, and best-fit scenario.

Smooth / in-place migration (平滑迁移)

The system architecture stays unchanged; algorithms are swapped gradually underneath it. This fits elastic, software-defined estates such as cloud platforms and CDNs, where libraries and configuration can be rolled forward without redesigning the application. A typical sequence is: upgrade the crypto library → enable protocol negotiation → canary on a slice of traffic → shift traffic progressively → full cutover → retire legacy.

CN example. A cloud platform migrates its TLS termination smoothly: it deploys a PQC-enabled OpenSSL build, runs a canary, shifts traffic gradually while monitoring performance, completes the rollout, and keeps an ECC fallback configured at lower negotiation priority for any client that cannot yet do PQC.

Phased migration (分阶段迁移)

Systems are migrated in batches ordered by business priority and quantum risk. This suits large, complex, heterogeneous estates where a single cutover is infeasible.

CN example. A government system migrates in three phases: 2025–2027 covers identity authentication and the e-government extranet; 2028–2030 covers data-exchange platforms and core business systems; 2030 onward covers peripheral and office systems.

Hybrid cryptography (混合密码方案)

Classical and post-quantum algorithms run together as a double-insurance: the channel stays secure as long as either algorithm resists attack. This fits ultra-high-assurance systems and early migrations where PQC implementations are not yet fully battle-tested. Methods include algorithm combination (for example ECDH and ML-KEM shared secrets fed through a KDF), protocol nesting, and layered encryption. See hybrid cryptography.

CN example. A digital-currency exchange uses hybrid throughout: key agreement combines ECDH with ML-KEM; transactions carry dual signatures (ECDSA plus ML-DSA); and stored data is protected with AES-256 alongside a Classic McEliece key-encapsulation layer.

Choosing a path

The report identifies the factors that should drive path selection for each system:

• Business criticality and risk — how damaging is exposure, and how long must the data stay confidential.
• Architecture complexity — monoliths and embedded systems resist smooth migration.
• PQC maturity and performance — whether vetted, performant implementations exist for the target platform.
• Cost — engineering, hardware (HSM refresh), and operational overhead.
• Compliance — domestic and sector mandates that set deadlines or require specific algorithms.

Standards & references

• 安全牛《后量子密码安全能力构建技术指南（2025版）》 — industry report; the framework, principles, and paths above are synthesized and rewritten from it, not reproduced. It uses the former algorithm names CRYSTALS-Kyber, CRYSTALS-Dilithium, and SPHINCS+ for what NIST now standardizes as ML-KEM, ML-DSA, and SLH-DSA.
• NIST Post-Quantum Cryptography project — the standardized algorithm suite.
• CISA / NSA / NIST — Quantum-Readiness: Migration to PQC — inventory and roadmap guidance.
• Resources — full standards register