What is post-quantum cryptography (PQC)?

Why it is needed

Many current encryption algorithms are secure because conventional computers struggle to factor large numbers. A powerful enough quantum computer could find those factors far faster, according to an explainer from the U.S. National Institute of Standards and Technology (NIST). No one knows when such a machine will exist. NIST says expert estimates run from a few years to a few decades. The risk begins earlier, because an adversary can capture encrypted data today and keep it until a quantum computer can unlock it. NIST calls that approach "harvest now, decrypt later."

The standards

NIST is standardizing the replacements. The agency says it assessed 82 algorithms from 25 countries. It published its first three finished standards on August 13, 2024:

• FIPS 203 (ML-KEM), intended as the primary standard for general encryption
• FIPS 204 (ML-DSA), intended as the primary standard for digital signatures, which are used to authenticate identity
• FIPS 205 (SLH-DSA), a hash-based signature standard intended as a backup to ML-DSA

In March 2025, NIST selected HQC, which is based on error-correcting codes, as a backup to ML-KEM. It said it expected a final standard in 2027. Another signature standard, FIPS 206, built around the FALCON algorithm, was still listed as in development on NIST's project page in October 2026. The page was last updated on August 5, 2026.

Where things stand in 2026

U.S. federal deadlines moved earlier in 2026. An executive order signed on June 22, 2026 tells the Office of Management and Budget to issue guidance. That guidance is to require each federal agency to move its high value assets and high impact systems to PQC. It is to require this for key establishment (agreeing on shared secret keys) by December 31, 2030. For digital signatures the date is to be December 31, 2031. IEEE Spectrum reported that this pulls forward an earlier federal deadline of 2035.

In guidance published in March 2025, the United Kingdom's National Cyber Security Centre advises organizations to finish discovery and initial planning by 2028. It advises them to carry out their highest-priority migrations by 2031 and complete the switch by 2035.

Google has set an earlier target. The company said in March 2026 that it was introducing a 2029 timeline for PQC migration. It cited progress in quantum hardware, quantum error correction and estimates of the resources needed for quantum factoring.