Post-Quantum Cryptography (PQC)

Post-quantum cryptography (PQC) is the family of cryptographic algorithms built to withstand a large-scale quantum computer. Today's public-key cryptography - the RSA and elliptic-curve math behind TLS key exchange and digital signatures - relies on problems a quantum computer could solve efficiently, so it would fall the day such a machine arrives. PQC replaces that math with problems (most prominently structured lattices) that remain hard for quantum and classical computers alike. In 2024 NIST finalized the first standards: ML-KEM (FIPS 203) for key encapsulation and ML-DSA (FIPS 204) for signatures.

PQC matters now because of the 'harvest now, decrypt later' threat: an adversary can record encrypted traffic today and decrypt it once quantum hardware exists. Data with a long secret lifetime - regulated audit trails, sensitive records, credentials - is therefore already at risk. The common migration path is 'hybrid' key exchange, combining a classical algorithm with a post-quantum one so a session is safe unless both are broken. For an AI governance boundary, PQC keeps two things trustworthy into the quantum era: the confidentiality of governed traffic in transit, and the integrity of the signed audit ledger that has to stand as evidence for years.