Post-Quantum Cryptography (PQC)

Post-quantum cryptography is the field of cryptographic algorithms designed to withstand attack by quantum computers. In August 2024 the US standards body NIST finalized its first three standards, FIPS 203, 204, and 205, covering the ML-KEM key encapsulation scheme and the ML-DSA and SLH-DSA signature schemes.

Why it matters

Today's public-key cryptography, including the elliptic curve signatures securing bitcoin, would fall to Shor's algorithm on a sufficiently large quantum computer. PQC schemes rest on different mathematics, chiefly lattices and hash functions, believed resistant to quantum attack. Migration is a decade-scale project: US federal systems target completion around 2035, and the harvest now, decrypt later threat means long-lived secrets need protection well before such a machine exists.

For bitcoin, the challenge is less inventing algorithms than deploying them. Post-quantum signatures are much larger than Schnorr or ECDSA signatures, straining block space, and proposals for quantum-resistant address types would require a coordinated soft fork and voluntary migration of coins.

In the gold vs bitcoin debate

PQC is bitcoin's answer to the strongest technical argument gold holds over it. Gold requires no cryptographic migration because it requires no cryptography. Bitcoin's rebuttal is adaptability: signatures are a replaceable component, and the network has years of warning through public qubit milestones. Which argument persuades depends on one's confidence in coordinated software governance.