Google's Quantum AI Cuts Bitcoin's Security Threshold — What It Means for Crypto

Google's Quantum AI team has released a blog post and whitepaper revealing that breaking Bitcoin's blockchain encryption may require significantly less computing power than previously believed. The findings are raising urgent questions about the real-world timeline for quantum threats to cryptocurrency security.

Earlier estimates suggested that cracking Bitcoin or Ethereum's cryptographic protections would take millions of quantum bits, or qubits. Google's new research narrows that figure dramatically, suggesting fewer than 500,000 physical qubits could be sufficient — and that targeted attacks might only need between 1,200 and 1,450 high-quality qubits. This puts the gap between today's quantum hardware and a viable attack closer than most investors and developers have assumed.

The attack scenarios outlined in the whitepaper are particularly concerning because they target live transactions rather than dormant wallets. When a Bitcoin transfer is initiated, a public key becomes briefly visible on the network. Google's model shows that a sufficiently advanced quantum computer could use that window — roughly nine minutes — to derive the private key and redirect funds before the original transaction confirms. Given Bitcoin's average 10-minute confirmation time, attackers could theoretically succeed about 41% of the time.

Bitcoin's 2021 Taproot upgrade, designed to improve transaction efficiency and privacy, may have inadvertently widened the attack surface. By making public keys visible on-chain by default, Taproot potentially exposes a greater number of wallets to future quantum exploits. Researchers estimate that approximately 6.9 million Bitcoin — nearly one-third of the total supply — already have exposed public keys in some form.

To responsibly disclose its findings without enabling misuse, Google employed a zero-knowledge proof technique, allowing independent verification of results without revealing the actual method.

With Google previously flagging 2029 as a milestone year for capable quantum systems, the message to the crypto industry is clear: the window for migrating to quantum-resistant security standards is narrowing faster than expected.