Post-quantum cryptography
PQC
Cryptographic algorithms designed to resist attacks by both classical and quantum computers. PQC runs on ordinary hardware today — it is not quantum technology, it is classical maths chosen because no efficient quantum attack against it is known.
In practice
ML-KEM and ML-DSA are post-quantum. RSA and elliptic-curve cryptography are not.
Related terms
The NIST-standardised post-quantum key encapsulation mechanism, used to establish a shared secret over an untrusted network. It is the replacement for RSA key transport and elliptic-curve Diffie-Hellman.
The NIST-standardised lattice-based digital signature algorithm, intended as the general-purpose post-quantum replacement for RSA-PSS and ECDSA. Signatures are larger than ECDSA but performance is practical for most uses.
A stateless hash-based post-quantum signature scheme whose security depends only on the strength of its underlying hash function. Signatures are large and slow, but the security assumptions are the most conservative of the NIST signature standards.
A method of exchanging keys using quantum physics, where eavesdropping disturbs the transmission detectably. QKD needs dedicated hardware and links, and is not a substitute for post-quantum cryptography — the NSA does not recommend it for national-security systems.