Post-quantum cryptography (PQC) refers to cryptographic algorithms that resist attacks from quantum computers running Shor's algorithm. Current widely deployed public-key algorithms (RSA, ECC, Diffie-Hellman) rely on the difficulty of integer factoring and discrete logarithms — problems that Shor's algorithm can solve in polynomial time on a sufficiently large fault-tolerant quantum computer. In 2024, NIST finalized four post-quantum cryptographic standards: ML-KEM (CRYSTALS-Kyber) for key encapsulation, ML-DSA (CRYSTALS-Dilithium) and SLH-DSA (SPHINCS+) for digital signatures, and FN-DSA (FALCON) for signatures. Migrating to these algorithms is urgent because of "harvest-now-decrypt-later" (HNDL) attacks, where adversaries record encrypted traffic today to decrypt it once quantum computers become available. PQC is a classical software problem — it doesn't require a quantum computer to implement.
Related Terms
Shor's Algorithm
AlgorithmsA quantum algorithm for integer factorization with exponential speedup over the best known classical algorithms.
QPU
HardwareQuantum Processing Unit — the physical hardware chip that executes quantum circuits.
Quantum Advantage
FundamentalsA demonstrated speedup or improvement where a quantum computer outperforms the best classical algorithm on a practical task.