01Overview
In 1994 Shor’s algorithm showed that a quantum computer could factor large integers and compute discrete logarithms in polynomial time, which would break RSA and ECC. In 2016 NIST began standardising post-quantum cryptography; in 2022 the first algorithms were chosen; in 2024 ML-KEM, ML-DSA and SLH-DSA were published.
The hard part of migration is not the algorithms but the deployment: certificates, protocols, hardware and legacy systems all need updating. The industry talks about “harvest now, decrypt later” — ciphertext captured today may be opened by a quantum computer later. Hence hybrid key exchange and crypto-agility are the keywords of the transition.
02History
- 1994
Shor's algorithm
Quantum factoring and discrete logarithms.
- 2016
The NIST PQC competition
Standardisation begins.
- 2022
The first algorithms are chosen
Kyber, Dilithium and others.
- 2024
The FIPS standards arrive
ML-KEM, ML-DSA and SLH-DSA.
03Core concepts
Lattice cryptography
Built on hard problems in high-dimensional lattices, such as LWE and SIS.
Hash-based signatures
One-time or few-time schemes built only from hash functions.
Hybrid key exchange
Run classical and post-quantum algorithms together to avoid a single point of failure.
04Hands-on
Do it once — it beats reading it ten times
Swap one key exchange in a test server to hybrid X25519 + ML-KEM and confirm both sides agree
05Self-check
Say it in your own words first, then open the answer. Whatever you cannot explain is what to review next.
Can you explain "Lattice cryptography"?
Built on hard problems in high-dimensional lattices, such as LWE and SIS.
Can you explain "Hash-based signatures"?
One-time or few-time schemes built only from hash functions.
Can you explain "Hybrid key exchange"?
Run classical and post-quantum algorithms together to avoid a single point of failure.
What problem did it solve, and why was there nothing better at the time?
Go back to the history section: how was this done before, and what did it cost?
If you had to build it today, how would you break it down?
Use the hands-on task above: write a plan of at most three steps before you start.
06Key people
Peter Shor
1963 –
Proposed the quantum factoring algorithm.
Tanja Lange
1971 –
Post-quantum cryptography and cryptanalysis.
07Further reading
- Post-Quantum Cryptography
- NIST FIPS 203 / 204 / 205