Bitcoin and quantum computing

Original Article ↗ Hacker News Discussion ↗

Likelihood and Timeline of Cryptographically Relevant Quantum Computers (CRQC)

  • Posters treat probabilities as “psychological,” not objective; estimates for CRQC by 2030–2045 vary widely.
  • Some argue CRQC is inevitable and timelines recently moved earlier due to new results and multiple hardware approaches.
  • Others stress remaining physical and engineering hurdles and say practical impossibility is still plausible.
  • Unclear consensus: risk is non‑zero, timing highly uncertain.

Core Threat Model to Bitcoin

  • CRQC breaking ECDSA would allow recovery of private keys from public keys and signatures.
  • Biggest concern: large, old, and “dead” wallets whose public keys have been exposed; they can’t be migrated automatically.
  • Potential attacks: mass theft, burning large wallets to tank confidence, or quiet selective theft/mining to avoid detection.
  • Several argue catastrophe for those coins is effectively guaranteed if no pre‑emptive migration happens.

Mitigation and Upgrade Proposals

  • General agreement: mitigation must happen before “Q‑day”; after signatures are broken, you can’t prove ownership.
  • Proposed tools: post‑quantum signatures (e.g. SHRINCS/SHRIMPS), quantum‑resilient commitments (Taproot work), ZK proofs of key/seed knowledge, and commit‑reveal schemes.
  • Ideas for legacy outputs: burning vulnerable coins, capping their spend rate (e.g. “Hourglass” style throttling), or long, messy recovery processes using off‑chain identity proofs and some form of committee/court.
  • All approaches struggle with scale (TPS limits), user coordination, and philosophical resistance to centralization.

Forks, Governance, and “Immutability”

  • Debate whether a rollback to pre‑attack state plus crypto change would still be “Bitcoin” or would destroy its immutability narrative.
  • Others note Bitcoin has already undergone contentious upgrades; longest‑chain consensus defines “Bitcoin” in practice.
  • Concerns that recovery mechanisms could introduce plutocracy, centralized “ownership courts,” or de‑facto KYC.
  • ETFs and custodians might coordinate a “new Bitcoin” based on their internal ledgers, sidelining self‑custody users.

Legal and Ethical Questions

  • Disagreement whether key‑cracking is “just math” or theft.
  • Counterpoints cite tax treatment, asset seizures, and real cases where using published seed phrases led to criminal charges.
  • Many assume courts will extend existing theft/fraud doctrines to cryptocurrency, but exact treatment of pure key‑guessing remains unclear.

Economic and Broader Context

  • Opinions split on whether burning or stealing large amounts would crash price or reduce supply and potentially support it.
  • Some note Bitcoin is mainly used as a speculative asset, not a payment rail, and is a small slice of global digital value.
  • Comparisons: centralized systems (banks, HTTPS, messaging) are expected to migrate to post‑quantum schemes more quickly than Bitcoin.