Bitcoin Faces Massive Quantum Risk

One-Third of Bitcoin Supply Has Exposed Public Keys

Blockchain analytics firm Glassnode has published research finding that 6.04 million $BTC, roughly 30.2% of Bitcoin's total issued supply and worth approximately $469 billion, sits in wallets with publicly visible cryptographic keys. That figure represents coins currently exposed to quantum risk at rest, while the remaining 13.99 million BTC, or 69.8%, shows no public-key exposure under the firm's methodology.

The framework centres on a single test. A coin is considered exposed when address reuse, partial spending, or custody behavior has already made the public key visible on-chain while the funds remain tied to the same address. If the public key is already visible, the coin is classified as exposed under this model. Glassnode is careful to note it is not forecasting an attack timeline. The firm stated: "This analysis does not take a position on whether, or when, practical quantum attacks against Bitcoin will become possible, nor should it be read as a statement on the security or solvency of any individual custodian."

Address Reuse at Exchanges Drives the Bulk of Exposure

Glassnode divides the 6.04 million Bitcoin into two categories. Structural exposure, covering outputs whose script type reveals the public key by design, accounts for 1.92 million BTC, or 9.6% of issued supply. Operational exposure, driven by address reuse, partial spending, and custody behavior, accounts for 4.12 million BTC, or 20.6%. Structurally exposed coins include early pay-to-public-key outputs associated with Bitcoin's pseudonymous founder Satoshi Nakamoto, legacy multisignature structures, and more recent Taproot outputs.

Exchanges represent the sharpest pressure point in the operational category. Glassnode estimates about 1.66 million BTC held on exchanges falls into the exposed category, accounting for roughly 40% of all operationally exposed Bitcoin. Approximately half of labeled exchange-held BTC is in the susceptible bucket, compared with less than 30% of non-exchange supply. The variation across platforms is stark. Among major exchanges, Coinbase's labeled balances show only 5% exposure, while Binance sits at 85% and Bitfinex at 100%. Fidelity and CashApp sit near 2% exposed, Grayscale at roughly 50%, and Robinhood and WisdomTree at 100%. By contrast, the US, UK, and El Salvador all show 0% quantum exposure under Glassnode's methodology.

The good news is that much of the operational exposure is reversible. Glassnode said the operational exposure trend at exchanges is "straightforwardly reversible through standard address-management practices," including avoiding address reuse and rotating change outputs, and framed these as present-day operational choices rather than protocol-level changes. On the developer side, the Bitcoin developer community is debating protocol-level responses, including a proposed update known as BIP-360 that would introduce more quantum-resistant transaction formats.

Sources:
Blockspace Media: Glassnode says 30.2% of issued Bitcoin is exposed to quantum risk at rest
Decrypt: Nearly $500B in Bitcoin Is Exposed to Future Quantum Computing Attacks
Crypto Briefing: 6.04 million Bitcoin exposed to quantum risk, says Glassnode