Post-Quantum Cryptography (PQC)
Post-quantum cryptography develops cryptographic algorithms resistant to attacks by quantum computers, which threaten to break current public-key cryptography.
Post-[Quantum [Cryptography](/en/terms/quantum-cryptography)](/en/terms/post-quantum-cryptography) (PQC) refers to cryptographic systems designed to be secure against both classical and quantum computer attacks. Quantum computers running Shor's algorithm could break RSA and ECC in polynomial time, threatening current [blockchain security](/en/terms/blockchain-security).
Main PQC approaches include: lattice-based (CRYSTALS-Kyber, CRYSTALS-Dilithium—NIST selected), hash-based signatures (SPHINCS+—conservative, well-understood security), code-based (Classic McEliece—long-studied but large keys), and multivariate polynomial systems.
NIST standardized PQC algorithms in 2024: Kyber (key encapsulation), Dilithium (signatures), SPHINCS+ (stateless hash-based signatures), and Falcon (compact signatures). Migration is beginning for critical systems.
Blockchain implications include: replacing ECDSA with PQC signatures (larger signatures increase block space needs), updating key derivation, and handling the 'harvest now, decrypt later' threat (encrypted data stored today could be decrypted when quantum computers arrive). Timeline estimates for cryptographically-relevant quantum computers range from 10-30 years.
graph LR
Center["Post-Quantum Cryptography (PQC)"]:::main
Pre_cryptography["cryptography"]:::pre --> Center
click Pre_cryptography "/terms/cryptography"
Pre_quantum_computing["quantum-computing"]:::pre --> Center
click Pre_quantum_computing "/terms/quantum-computing"
Rel_blockchain_security["blockchain-security"]:::related -.-> Center
click Rel_blockchain_security "/terms/blockchain-security"
Rel_decoherence["decoherence"]:::related -.-> Center
click Rel_decoherence "/terms/decoherence"
Rel_security_operations_center_soc["security-operations-center-soc"]:::related -.-> Center
click Rel_security_operations_center_soc "/terms/security-operations-center-soc"
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🧒 Explain Like I'm 5
Current passwords can be cracked by future super-fast quantum computers. PQC is a new type of 'super-shield' math that even those powerful quantum computers can't break.
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