What Bitcoin Did
The Truth About Quantum Computing & Bitcoin | Brandon Black
- Quantum computers exploit superposition of qubits to solve cryptographic problems exponentially faster than classical computers, but scaling from theoretical to practically useful devices remains the fundamental bottleneck.
- The highest number factored by quantum computers to date is 21 (achieved in 2012); a 6-bit elliptic curve key was recently solved, showing minimal real-world progress despite billions in investment.
- Bitcoin's vulnerability depends on attack speed: public keys exposed on-chain (pay-to-pubkey addresses, ~2M coins) are at risk immediately; others remain safe as long as quantum attacks take longer than ~10 minutes per block.
- Post-quantum cryptography solutions exist (hash-based, lattice-based) but require multi-kilobyte keys and signatures compared to Bitcoin's current 100-byte total, creating severe blockchain throughput trade-offs.
- A soft fork using BIP360 (quantum-resistant taproot variant) could be the next Bitcoin upgrade, solving multiple problems simultaneously and potentially shifting narratives away from ossification concerns.