Google Study Warns of Quantum Threat to One-Third of Bitcoin Supply

A Google Quantum AI whitepaper has shed light on the vulnerability of Bitcoin to quantum attacks. The research, published in March 2026, estimates that roughly 6.9 million BTC - about one-third of the total supply - are sitting in addresses vulnerable to quantum 'at-rest' attacks.

The study found that breaking Bitcoin's 256-bit elliptic curve cryptography may require fewer than 500,000 physical qubits, a significant reduction from prior estimates.

Satoshi Nakamoto's coins are particularly exposed due to the design choice made in Bitcoin's first days. The mining software sent block rewards to P2PK (Pay-to-Public-Key) outputs, which store the full public key permanently visible on the blockchain.