Coinbase warns up to 6.9 million BTC at risk from future quantum attacks

Coinbase’s latest security analysis says that between 6.5 million and 6.9 million Bitcoin could be exposed to future quantum‑computer attacks. The vulnerability applies to addresses where the public key is visible on‑chain – such as Pay‑to‑Public‑Key (P2PK) formats and wallets that repeatedly reuse the same address – because a sufficiently powerful quantum computer could use Shor’s algorithm to break the ECDSA signatures that prove ownership.

The report notes that the practical feasibility of such attacks depends on the development of fault‑tolerant quantum processors; recent estimates suggest that fewer than 500,000 physical qubits might be enough to compromise the secp256k1 curve. Coinbase therefore recommends an early migration to post‑quantum cryptographic schemes. It assesses the risk to Bitcoin’s proof‑of‑work mining (SHA‑256) as less acute, being primarily linked to Grover‑type speed‑ups rather than a direct break of signatures.