About 7.12 million bitcoin, or 35.4% of the current supply, have public keys visible on Bitcoin’s public ledger and could theoretically be targeted by sufficiently powerful quantum computers in the future, Glassnode data show. Address reuse is a major source of exposure. Some holdings could be moved to new addresses, but an estimated 1 million BTC linked to Satoshi Nakamoto may not be movable in the same way.
Address reuse accounts for 25.8% of supply
Glassnode defines quantum-exposed supply as bitcoin whose public keys are visible and could, in theory, be threatened by future quantum computing. A public key is information used to verify transactions. The figures do not mean these coins can be cracked or transferred with today’s computing capabilities. The risk depends on whether quantum computers become powerful enough to break the cryptographic protections in use.
Glassnode estimates that 25.8% of bitcoin’s total supply is exposed because addresses have been reused. Moving those coins to new addresses can address the ongoing exposure tied to the original public keys. The data do not include a timeline for when quantum computers might reach the capabilities required, so they indicate the potential scale of the risk, not losses that have already occurred.
Exposure varies across exchanges and platforms
About 11.6% of bitcoin held by exchanges is in addresses with exposed public keys, according to Glassnode. Based on the firm’s entity attribution data, the corresponding figures are 100% for Robinhood, 85% for Binance and about 5% for Coinbase. Bitcoin held by the U.S. government showed no such exposure. Glassnode cautioned that these percentages are not security ratings; they measure exposure among addresses attributed to each entity under its methodology.
Coinbase custodies bitcoin for most U.S. spot bitcoin ETFs. A company analyst has warned about the quantum threat, and CEO Brian Armstrong said on October 29 that Coinbase had begun work on post-quantum upgrades to its custody systems. For large custodians, the issue involves not only the technical approach but also how client assets would be managed and migrated. Public information does not specify the upgrade’s progress or completion date.
Bitcoin linked to Satoshi presents a separate challenge
Coins exposed through address reuse can be moved to new addresses in a transaction. An estimated 1 million BTC linked to Satoshi Nakamoto are considered unable to move in this way, leaving them without the same option. The available data do not say whether these coins will be transferred or identify a specific solution for these holdings.
The analysis measures the extent of public-key exposure and the associated potential technology risk; it does not indicate that Bitcoin has been attacked by quantum computers. For exchanges, custodians and ETF-related holdings, the data provide exposure rates for attributed addresses. How post-quantum upgrades will be implemented—and how immovable legacy holdings could be addressed—remains unclear.