Learn
Post-quantum, in plain English
Short guides for the people who have to make decisions about it. Start anywhere.
Guide 1
What is post-quantum cryptography?
The short version.
The problem
Public-key cryptography, such as RSA and elliptic curves, protects web traffic, payments and digital identity. A large enough quantum computer could break it.
The fix
New algorithms built on maths that quantum computers are not known to solve efficiently. NIST published the first standards, FIPS 203, 204 and 205, in August 2024.
The catch
They run on today’s computers, but every system, product and supplier using the old methods has to switch. The NCSC wants that finished by 2035.
Why the new maths is hard to break
ML-KEM and ML-DSA are built on lattice problems like the one shown here: find the point nearest the ring. It is easy in two dimensions. In the hundreds of dimensions real systems use, no efficient method is known, classical or quantum.
Test yourself
What breaks, and what holds
Quantum computing does not break all cryptography. Tap each card to see which parts are at risk.
Sources: NIST, FIPS 203, 204 and 205; Google Research, March 2026; RFC 10024.
What leaders learn to oversee
The migration journey
Five stages every post-quantum programme goes through. Our sessions show leaders what each one involves and what to ask for.
- 1
Find your cryptography
Most organisations do not know everywhere they use cryptography. An inventory of systems, protocols, certificates and keys comes first. It is the heart of the NCSC’s first milestone, 2028.
- 2
Decide what moves first
Rank systems by how long their data must stay secret and how critical they are. Long-lived secrets are the ones that harvesting puts at risk.
- 3
Ask your suppliers
Much of your cryptography sits inside products you buy. Ask suppliers for their post-quantum plans and dates, and build the answers into contracts.
- 4
Migrate, starting hybrid
A common first step is hybrid key exchange: a conventional method and ML-KEM combined, so a connection stays protected if either one is broken.
- 5
Prove progress
Boards need evidence: what has moved, what is left, and whether the plan meets the 2031 and 2035 milestones.
Where does your organisation stand?
Five questions, based on the first NCSC milestone. Your answers stay in your browser: nothing is sent or stored.
- Do you know where your organisation uses public-key cryptography, in its own systems and in what it buys?
- Do you know which of your data must stay confidential for ten years or more?
- Have you asked your most important suppliers about their post-quantum plans?
- Is one named executive accountable for the migration?
- Has your board or executive team been briefed on the NCSC’s 2028, 2031 and 2035 milestones?