POST-QUANTUM CRYPTOGRAPHY, EXPLAINED
A plain-English field guide to the cryptographic transition: what changes, what stays, and why it matters before quantum computers arrive.
Explore three scenarios ↓Quantum-resistant cryptography takes over the public-key jobs—not every part of encryption.
FIELD GUIDE / 01
Post-quantum cryptography can sound abstract. But it appears in ordinary moments: opening a website, installing software, and storing a confidential file.
The transition is not a swap of one universal key. Each system combines different tools, and only the vulnerable public-key jobs need new mathematics.
When you visit a website
Server proves its identity
X25519 or ECDH agrees a secret
AES encrypts the session
Keep the current certificate
Add ML-KEM to secret agreement
AES still encrypts the session
ML-DSA proves identity
ML-KEM agrees a secret
AES still encrypts the session
The public-key handshake changes. The fast encryption protecting the page stays.
When a device installs code
SHA-256 fingerprints the package
ECDSA signs the release
Device verifies the publisher
Keep the existing signature
Add an ML-DSA signature
Device checks both signatures
SHA-256 fingerprints the package
ML-DSA signs the release
Device verifies the publisher
Code signing is about trust, not secrecy. The signature is the piece that evolves.
When a document must stay private
Create a random file key
AES-256 encrypts the document
RSA protects the small file key
AES-256 keeps protecting the file
Protect the file key twice
Use RSA and ML-KEM together
Create a random file key
AES-256 encrypts the document
ML-KEM protects the file key
The document encryption remains familiar. It is the wrapped file key that must change.
FIELD NOTES / 02
These are the U.S. NIST standards that define the new public-key building blocks. Names matter less than the job each one performs.
Some information must remain secret for years or decades.
Use hybrid systems while platforms and partners catch up.
Use quantum-resistant public-key cryptography for long-lived trust.
WHY MOVE NOW?
Attackers can capture encrypted information now and hold it until future quantum capability can attack today’s public-key systems. Migration takes time—so long-lived data needs a plan before the deadline is visible.
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