Google says under 500,000 physical qubits could break Bitcoin and Ethereum cryptography

Google published research on Monday revising the quantum resources it believes are needed to break 256-bit elliptic-curve cryptography used by Bitcoin and Ethereum. The paper estimates that fewer than 500,000 physical qubits could be sufficient under its current hardware assumptions, and it models an “on-spend” Bitcoin key-recovery window of about 9–12 minutes. It also warns Ethereum’s account model exposes public keys in a way that could enable “at-rest” attacks, estimating the 1,000 richest exposed accounts holding about 20.5 million ETH could be compromised in under nine days.