More than 6 million bitcoin, representing 31.2% of circulating supply, sit behind public keys already visible on-chain, according to data circulated by Glassnode this week. The figure is roughly 5 to 6 percentage points above the low reached in 2023, and the pool is now worth hundreds of billions of dollars at recent market prices.

How much has the exposed supply grown?

Glassnode co-founder Rafael Schultze-Kraft said exposed supply has increased by 222,000 BTC (approximately $18.2 billion) since the firm's May report. Over the same period, total bitcoin supply grew by just 64,000 BTC, meaning the exposed share has expanded faster than the network itself.

The figures measure address usage, not immediate security risk. No practical attack on bitcoin or ether wallet keys has been demonstrated, and the cryptographic primitives underpinning both networks remain unbroken.

Where are the largest concentrations?

Exchanges account for the bulk of the recent increase. They now hold 1.79 million BTC behind visible public keys, with 123,000 BTC of the growth since May coming from exchange-controlled wallets.

The breakdown varies sharply by venue:

• Coinbase: 10% exposed
• Binance: 83% exposed
• Grayscale: 49%
• Revolut: 99%
• Robinhood: 100%

Fidelity holds approximately 375,000 BTC with just 2% exposed. Government holdings tracked by Glassnode — including those of the United States, United Kingdom and El Salvador — show no exposure under this methodology.

What makes a public key visible?

Public keys can become visible through address reuse or appear directly in certain bitcoin output types. These include early pay-to-public-key (P2PK) outputs from the network's first years and Taproot transactions.

A sufficiently capable quantum computer, or a hypothetical mathematical breakthrough, could allow an attacker to derive the corresponding private keys from a visible public key. That would hand the attacker control of the associated funds without needing the holder's signature.

What are researchers warning about?

Ethereum researcher Justin Drake urged the industry to prepare for what he called "bunker mode." Drake argued that AI could uncover a shortcut to breaking wallet cryptography "in months, not years" in a worst-case scenario, well before cryptographically relevant quantum computers arrive.

The warning lands against a backdrop of mounting institutional holdings. The growth in exposed supply has outpaced the growth in total supply, which compresses the operational window for any future migration to quantum-resistant address formats.

What happens next?

Each new transaction that reuses an address, or spends from a P2PK output, adds to the pool of exposed keys. The market-structure question is whether custodians, exchanges and protocol developers will coordinate a transition before a credible threat materializes, or respond reactively.

The next material signal to watch is any announcement from a major exchange or wallet provider on a roadmap for moving funds into post-quantum signature schemes, or a formal standards proposal for a new bitcoin address type.