Overview
- Google Quantum AI’s whitepaper, published Tuesday, says cracking the secp256k1 signatures used by Bitcoin and many chains could take about 1,200–1,450 logical qubits and fewer than 500,000 physical qubits.
- A fast superconducting machine could run an “on‑spend” attack in roughly nine minutes after a transaction reveals a public key, a window that rivals Bitcoin’s 10‑minute block time.
- The paper flags large stores of exposed value, including about 1.7 million BTC in old pay‑to‑public‑key outputs and major Ethereum risks such as 20.5 million ETH in top accounts and roughly 37 million ETH in validator stake.
- To avoid handing attackers a blueprint, the team withheld the attack circuits and used a zero‑knowledge proof so others can verify the resource counts without seeing the design.
- No machine can do this today, but Google set a 2029 target for its own post‑quantum shift, Ethereum is advancing a PQC roadmap, and Bitcoin developers are discussing tools like BIP‑360 while urging better key hygiene and faster migration planning.