Nearly one-third of all Bitcoin in circulation-over six million coins worth roughly $469 billion-is already vulnerable to theft if powerful quantum computers become a reality, according to research by blockchain analytics firm Glassnode.
The analysis examined the Bitcoin blockchain to determine which coins have had their public cryptographic keys exposed. It found 6.04 million BTC, or 30.2% of the issued supply, is exposed to quantum risk. The remaining 13.99 million BTC shows no public-key exposure.
The concern stems from Bitcoin's security architecture. Each coin is controlled by a private key matched to a public key visible on the blockchain only under certain conditions. A sufficiently capable quantum computer using Shor's algorithm could recover a private key from a known public key. Any coin whose public key has been revealed on-chain would be immediately targetable.
Glassnode separates the exposed supply into two categories. Structural exposure accounts for 1.92 million BTC-9.6% of the issued supply. These are coins locked in script formats that reveal the public key by design, including early pay-to-public-key outputs associated with Satoshi Nakamoto, legacy multisignature structures, and recent Taproot outputs.
The larger and more actionable category is operational exposure, totaling 4.12 million BTC-20.6% of the issued supply. These coins became vulnerable through address reuse, where a wallet receives multiple transactions at the same address.
Exchanges account for roughly forty percent of operationally exposed Bitcoin. Coinbase's labeled balances appear largely concentrated in non-exposed structures, with only five percent exposed. Binance and Bitfinex show comparatively high susceptible balances at 85% and 100%, respectively. Sovereign Bitcoin holdings fared better: the US, UK, and El Salvador all show zero quantum exposure.
Estimates for Q-Day-when a quantum computer comes online powerful enough to crack blockchain cryptography-range from 2030 to 2032 and beyond. On Thursday, the US government announced over two billion dollars in investment into quantum startups and planned foundries.