Google Cuts Bitcoin Break Estimate to Under 500,000 Qubits as Researcher Cracks 15-Bit Key
Updated
Updated · FinanceFeeds · Aug 21
Google Cuts Bitcoin Break Estimate to Under 500,000 Qubits as Researcher Cracks 15-Bit Key
3 articles · Updated · FinanceFeeds · Aug 21
Summary
Google Quantum AI’s March 2026 paper said breaking Bitcoin’s ECDSA-256 could require fewer than 500,000 physical qubits—about 20 times fewer than 2019 estimates.
A 41% simulated success rate for hijacking a transaction within Bitcoin’s 10-minute confirmation window sharpened concern, especially because about 6.9 million BTC, or 32% of supply, sit in wallets with exposed public keys.
Giancarlo Lelli added a real-world milestone on April 24 by cracking a 15-bit elliptic-curve key on public quantum hardware and collecting a 1 BTC bounty, though Bitcoin’s 256-bit encryption remains far beyond current machines.
Bitcoin developers are weighing BIP 360, a quantum-resistant address standard, but a full post-quantum migration could take five to seven years and may move slower than Ethereum’s more flexible upgrade path.
Adam Back still puts a practical threat 20 to 40 years away, even as NIST plans to deprecate current encryption by 2030 and Google aims to shift its own systems to post-quantum cryptography by 2029.