Post-quantum cryptography · PQC
What is post-quantum cryptography?
Post-quantum cryptography is a new generation of cryptographic algorithms designed to resist attacks from both classical and quantum computers. The first standards are final; the work now is finding where change is needed.
PQC protects familiar systems with new mathematics.
Most internet security depends on public-key algorithms such as RSA and elliptic-curve cryptography. A sufficiently capable quantum computer could use Shor's algorithm to defeat the mathematical problems that protect those systems. No such cryptographically relevant quantum computer is known to exist today, but replacing cryptography across software, infrastructure, devices and suppliers can take years.
Definition · Post-quantum cryptography
PQC is not the same as quantum key distribution. It is software-compatible cryptography that can be deployed through the systems organizations already operate.
The first NIST standards are ready to use.
In August 2024, NIST finalized three Federal Information Processing Standards. ML-KEM establishes shared secrets for encryption. ML-DSA and SLH-DSA provide digital signatures. NIST says organizations should begin transitioning now.
| Standard | Purpose | Based on |
|---|---|---|
| FIPS 203 · ML-KEM | Key establishment | CRYSTALS-Kyber |
| FIPS 204 · ML-DSA | Digital signatures | CRYSTALS-Dilithium |
| FIPS 205 · SLH-DSA | Digital signatures | SPHINCS+ |
These standards do not make every implementation automatically secure. Protocol support, configuration, interoperability and operational controls still matter.
Public-key cryptography changes most.
Quantum risk is not uniform. RSA, Diffie–Hellman and elliptic-curve systems are the main migration focus because of Shor's algorithm. Symmetric encryption is affected differently; guidance generally addresses that risk with larger key sizes rather than replacing symmetric cryptography entirely.
The practical problem is visibility. Cryptography can be embedded in TLS certificates, APIs, VPNs, identity systems, code libraries, firmware, cloud services and third-party products. A migration plan cannot cover what an organization has not found.
Begin with discovery, not a wholesale replacement.
- 01
Set ownership
Give one accountable team authority to coordinate security, infrastructure, engineering, procurement and risk.
- 02
Build an inventory
Record algorithms, certificates, libraries, protocols, keys, owners and dependencies.
- 03
Prioritize
Use data sensitivity, secrecy lifetime, exposure and replacement difficulty to order the work.
- 04
Test and migrate
Validate performance and interoperability, then replace systems in controlled phases.
A cryptographic inventory creates the foundation. Crypto agility makes future replacements less disruptive, while a quantum readiness roadmap keeps priorities and evidence visible.
Questions leaders should ask now.
- Which public-key algorithms protect our data and identity today?
- Which data must remain confidential for many years?
- Can our vendors state their PQC support and migration plans?
- Where can we test standards-based algorithms without disrupting production?
- How will we prove progress to customers, auditors and leadership?
Primary sources
Turn knowledge into evidence
