GCRI · Quantum Technologies
Post quantum cryptography
Post-quantum cryptography replaces public-key algorithms that a future quantum computer could break with new classical algorithms designed to resist it. NIST has published standards, protocols are being updated, and organisations face a long migration across software, hardware and certificates. This page sets out the new algorithms, how migration is planned and measured, and what evidence serves the organisations and agencies carrying it out.
Post quantum cryptography on the record.
Post quantum cryptography: how the risk develops.
Transition security and algorithm standards. The dossier below sets out how the risk develops, what is measured, where the data come from, how it is modelled and who decides.
New hard problems
Post-quantum algorithms rely on mathematical problems, such as those on lattices or hash functions, for which no efficient quantum attack is known.
Larger keys and signatures
Many post-quantum schemes use larger keys or signatures than current ones, affecting bandwidth, storage and constrained devices.
Hybrid modes hedge risk
Combining a classical and a post-quantum algorithm keeps security if one is later broken, a common choice during transition.
Agility eases future change
Systems designed to swap algorithms easily reduce the cost of this migration and the next one.
Post-quantum migration tracker.
The screen a team would use to follow this subject: its measures, states and decisions. Names are examples and values are illustrative.
Post-quantum migration tracker
Post quantum cryptography · Crypto inventory · Wave 3
Migration
- Inventoryall crypto
- Prioritisedata lifetime
- Selectstandard algorithms
- Hybrid deployclassical and PQC
- Testinterop
- Cut overretire
Systems by priority
| Archive signing | RSA-2048 | 29 | ML-DSA hybrid | Piloting |
| VPN gateway | ECDH | 8 | ML-KEM hybrid | Planned |
| Payments HSM | RSA-3072 | 11 | Vendor roadmap | Blocked |
| Web TLS | ECDHE | 2 | Hybrid key exchange | Done |
Progress
Every domain that keeps secrets for decades must migrate.
- HealthCouplingPatient data has long confidentiality lifetimes.What to watchInventory of vulnerable algorithms
- EnergyCouplingLong-lived grid devices need upgradable cryptography.What to watchCrypto-agility of devices
- FoodCouplingTrade and payment systems rely on public-key infrastructure.What to watchPKI migration plans
Migration findings are designed for the Foresight Outlook series. NIST published FIPS 203, 204 and 205 in 2024 and selected HQC as an additional algorithm in 2025.
- Inventory and migration lessons.
- Interoperability test results.
How post quantum cryptography is modelled, measured and tested.
The model, its assumptions, its data and its uncertainty, in the form a scientist or engineer would check. Structures follow published methods. The values drawn are illustrative, not findings.
System model
The couplings between the systems in post quantum cryptography: signs of influence, a reinforcing and a balancing loop, and cross-links where stress jumps.
What is measured, and how well.
Each indicator carries its unit, its cadence, the kind of source behind it and the evidence label a value would carry. No values are shown: a programme supplies them under its own authority.
| Indicator | Unit | Cadence | Source type | Label |
|---|---|---|---|---|
| Standardised post-quantum algorithms | count | per standard release | NIST and other standards bodies | Published statistics |
| Protocols with post-quantum support specified | count | per assessment | IETF and other standards | Published statistics |
| Web traffic using post-quantum key agreement | percent of connections | monthly | Network measurements | OBSERVED |
| Organisations with migration plans | percent of surveyed organisations | per survey | Surveys | REPORTED |
| Cryptanalysis results against candidate schemes | count of significant attacks | per review | Cryptographic literature | REPORTED |
| Validated implementations | count | annual | Cryptographic module validation lists | Published statistics |
Where the evidence comes from.
Named public datasets and institutional records, each with its licence class. Sources by agreement are used only under their terms and never republished.
| Source | What it gives | Licence class |
|---|---|---|
| NIST post-quantum cryptography project and FIPS 203, 204 and 205 | Standards, documentation and additional selections | Public domain, US government |
| IETF post-quantum and hybrid protocol work | Integration into TLS, SSH and other protocols | Open, IETF Trust terms |
| National cyber agency migration guidance | Timelines and priorities | Public, terms per agency |
| Open Quantum Safe project | Open-source implementations for testing | Open source, MIT licence |
| Cloudflare Radar and similar measurements | Adoption in web traffic | Public, terms per provider (to check) |
Who decides, and what the evidence serves.
Quantum Technologies prepares evidence. The decisions below are taken by the authorities named, under their own rules, and never by the platform.
| Who decides | The question | Evidence this page serves |
|---|---|---|
| Organisations and security teams | Which systems to migrate first and how | Planning guides; performance comparisons |
| Standards bodies | Which algorithms and parameters to standardise | Cryptanalysis evidence |
| Vendors | When and how to ship post-quantum support | Adoption and protocol evidence |
Outputs this topic produces
- Migration planning guides with inventory and prioritisation steps
- Performance comparisons of standard algorithms
- Adoption tracking summaries
- Evidence notes on cryptanalysis of new schemes
What experts ask.
Migration questions start with an inventory.
- Where does an organisation use public-key cryptography, in which systems, protocols, devices and suppliers?
- Which data must remain confidential long enough to be at risk from future decryption?
- Which post-quantum algorithms are standardised, and what are their performance and size trade-offs?
- Should systems combine classical and post-quantum algorithms during the transition?
- Can systems change algorithms easily in future, a property known as crypto-agility?
Mechanisms and drivers.
Today’s public-key cryptography rests on mathematical problems, such as factoring large numbers, that are hard for classical computers but could be solved efficiently by a large quantum computer running known algorithms. Symmetric encryption and hash functions are much less affected and can be strengthened by using longer keys. The urgent problem is therefore key exchange and digital signatures.
Two pressures drive timing. The harvest-now, decrypt-later threat means confidential data intercepted today could be read once a capable machine exists. Migration time is long: cryptography is embedded in hardware, firmware, protocols and supply chains, and some devices stay in service for decades. If the time data must stay secret plus the time migration takes exceeds the time until a capable quantum computer exists, data is already at risk.
How it is studied, and where the methods stop.
| Method or data | What it shows | Limits |
|---|---|---|
| Cryptographic inventory and discovery tools | Where vulnerable algorithms are used | Embedded and third-party cryptography is easily missed |
| Cryptanalysis of candidate algorithms | Confidence in algorithm security | New algorithms have less analysis history; some candidates were broken during evaluation |
| Performance and interoperability testing | Key sizes, speed and protocol fit | Results vary with hardware and implementation |
| Risk-based migration planning | Priorities by data lifetime and system criticality | Depends on uncertain quantum timelines |
How it is studied, and what the methods cannot say.
- 01Cybersecurity and cryptographyCryptographic inventory · Migration prioritisation · QKD implementation reviewApplied here
- 02Quantum computing, sensing and communicationComparable benchmarking · Technology readiness assessment · Security implications trackingApplied here
- 03Probability and statisticsFidelity estimation · Testing advantage claims · Analysing patent and investment dataApplied here
Where this page’s references lead.
The bodies and documents this page is read against. Status and editions change; each link goes to the issuing body.
Where this page leads across the Consortium.
Questions and answers.
What did NIST standardise?
Is post-quantum cryptography quantum technology?
Why use hybrid schemes?
Do we need quantum computers to use post-quantum cryptography?
What is a hybrid approach?
Is the platform’s Universe mission theme on migration readiness active?
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