Quantum Computing Threatens Bitcoin Signatures — Devs Push Post‑Quantum Defenses

At ETH Denver, developers, security researchers and industry firms warned that quantum computing poses a credible threat to Bitcoin primarily by breaking elliptic-curve digital signatures (via Shor’s algorithm) rather than attacking hash functions like SHA-256. Panelists including BIP 360 co-author Hunter Beast and others highlighted that once a Bitcoin public key is exposed, a sufficiently powerful quantum computer could derive the private key and steal funds. Tracking firm Project Eleven estimates roughly 6.9 million BTC (about 30% of supply) sit in addresses with exposed public keys, creating substantial attack surface. Academic and industry estimates for required qubits have shifted: earlier studies suggested multi‑million physical qubits, while newer work (e.g., Iceberg Quantum) claims the threshold could fall to the six‑figure range — though practical attack feasibility depends on logical qubits, error rates, coherence and runtime. Industry responses include the Ethereum Foundation and exchanges forming post‑quantum teams, Coinbase advising migration and calling the problem solvable, and the BIP 360 proposal (now merged into the BIP repo) advocating Pay‑to‑Merkle‑Root (P2MR) outputs to reduce public‑key exposure and enable future post‑quantum signatures. Panelists warned governance challenges: many old or inactive addresses (including early‑mined coins) may never migrate, and proposals like freezing coins are politically fraught. Traders should note the core takeaway: the risk is real enough to require planning and mitigation, but is not yet an immediate, practical exploit — though a sudden arrival of practical quantum attacks before coordinated migration could trigger rapid sell pressure and severe market disruption.