Overview
- Google’s Quantum AI team reports that about 1,200–1,450 logical qubits could run Shor’s algorithm to break the elliptic‑curve signatures that secure Bitcoin, with a modeled theft window of roughly nine minutes after a transaction is broadcast.
- Google is urging a shift to post‑quantum cryptography by 2029, and Ethereum has live test networks and a public plan to complete its move on a similar timeline.
- Bitcoin’s upgrade faces tougher trade‑offs even with the BIP‑360 testnet, since many post‑quantum signatures are much larger and could cut a block from about 7,600 transactions to fewer than 400.
- The biggest exposure is in early addresses that revealed public keys on chain, covering about 1.7 million BTC including Satoshi‑era coins, with broader estimates raising the at‑risk pool to roughly 6.9 million.
- Investors are already rotating toward projects billed as quantum‑resistant with double‑digit gains reported, and Jefferies dropped Bitcoin from model portfolios citing quantum vulnerability.