Glassnode says about 30% of Bitcoin’s issued supply is exposed to quantum risk because the public keys linked to those coins are already visible on-chain. The analytics firm said most of that exposure is connected to address reuse, partial spending and custody practices rather than a weakness affecting the Bitcoin network as a whole.

In a new report on Bitcoin’s quantum-exposed supply, Glassnode measured 6.04 million BTC, or 30.2% of issued supply, held in addresses whose public keys have already been revealed on the blockchain. That figure is the basis for the roughly 30% headline around Bitcoin’s quantum exposure.

Under the same framework, the remaining 13.99 million BTC, or 69.8% of issued supply, shows no public-key exposure at rest. Those coins keep their public keys hidden until they are next spent, a property that matters because many Bitcoin output types reveal only a hash of the public key before spending.

Glassnode Quantifies Bitcoin’s Quantum-Exposed Supply

The estimate puts a supply figure on a long-running theoretical security concern. A sufficiently capable quantum computer that could break elliptic-curve cryptography could, in principle, derive a private key from an exposed public key. Glassnode’s analysis attempts to quantify how much Bitcoin currently sits in that exposed state.

The roughly 30% figure is not attributable to address reuse alone. Glassnode divides the exposed supply into two categories. The first is structural exposure, which it puts at 1.92 million BTC, equal to 9.6% of issued supply. That exposure is driven by script design, including the oldest pay-to-public-key formats.

The larger category is operational exposure. Glassnode estimates this bucket at 4.12 million BTC, or 20.6% of issued supply, and links it to address reuse, partial spending and custody behavior rather than script design. This is the part most directly connected to how holders and service providers use wallets.

That distinction is important for how the data is framed. Assigning the full 30.2% exposure figure to address reuse would overstate the mechanism. Only the 20.6% operational portion falls into that category, while the 9.6% structural portion is tied to the address type itself.

Why Address Reuse Matters in the Quantum-Risk Debate

Address reuse occurs when new funds are received at the same Bitcoin address that has already been used to send coins. Because spending from an address reveals its public key, any remaining balance or later funds sent back to that address are exposed at rest.

A supporting academic framework reaches the same conclusion. An arXiv paper on quantum exposure states that a coin is quantum-exposed exactly when its public key is visible on the blockchain. It also notes that address reuse leaves any remaining or future balance exposed after the first spend.

That means wallet behavior, not only the underlying script type, affects the level of exposure. A holder who avoids reusing addresses keeps a public key concealed until a transaction is made. Repeated reuse, by contrast, leaves the key visible on-chain for anyone, or any future machine, to examine.

Custody Practices and Market Context

For individual holders, the finding highlights the role of wallet hygiene, including using fresh addresses for each receive and avoiding reuse where possible. Custody providers face the same issue at a larger scale, because aggregated exchange balances can contribute to the operational-exposure bucket.

The analysis also feeds into a broader technical security discussion rather than a regulatory event. Developers have been considering migration paths such as the BIP-360 proposal for quantum-resistant outputs, which would represent a technical response to the type of exposure Glassnode measured. Any such migration would require coordination across wallets, exchanges and infrastructure providers because users and custodians would need practical ways to move coins into safer output types if standards change.

Market conditions remained subdued as the discussion circulated. Bitcoin was trading near $64,615, while the Fear & Greed Index stood at 26, classified as Fear. The quantum-risk framing had not translated into visible price action, according to the source report.

The debate comes during a cautious period for digital-asset markets, with attention still focused on fund flows after Bitcoin ETF outflows accelerated alongside a broad sell-off in risk assets and holders absorbed billions in realized losses during volatility. In that context, Glassnode’s figure functions as a long-horizon resilience metric rather than a warning of an imminent attack.