Bitcoin and quantum computing
Concerns over “cryptographically relevant” quantum computers are raising hard questions about Bitcoin’s long‑term security and governance. Commenters debate how likely it is that future quantum machines could derive private keys and seize coins, whether the network can realistically migrate to post‑quantum signatures in time, and what happens to dormant or early wallets that never upgrade. Ideas range from preemptive protocol changes and rate‑limiting vulnerable addresses to hard forks and custodian‑led rescues, alongside legal uncertainty over whether quantum‑enabled key cracking would count as theft under existing law.
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.