Post-quantum cryptography (PQC) is a class of encryption and digital-signature algorithms designed to remain secure even if large-scale quantum computers become practical. It is meant to replace or augment today’s public-key systems, such as RSA and elliptic-curve cryptography, which are widely used for secure connections, software updates, and identity verification.
PQC matters because a future quantum adversary could break much of today’s public-key cryptography, exposing long-lived secrets and trust chains. Defenders use PQC planning to reduce that risk by inventorying where cryptography is used, testing new algorithms, and building crypto agility so systems can be updated without major redesign. In real attacks, the concern is often “harvest now, decrypt later,” where encrypted data is collected today and saved for future decryption. PQC is the defensive answer to that threat model.