Quantum Threat Looms Over 6.9 Million Bitcoins

A recent Google Quantum AI whitepaper has shed light on a significant vulnerability in Bitcoin's security. The researchers found that approximately 6.9 million BTC, roughly one-third of the total supply, are sitting in addresses vulnerable to quantum 'at-rest' attacks.

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

The vulnerability stems from Satoshi Nakamoto's decision to use P2PK (Pay-to-Public-Key) addresses, which store the full public key in plain sight on the blockchain. This makes them susceptible to at-rest attacks, where an attacker can derive the private key without any time pressure.