Bitcoin public-key exposure rises to 35.4% of supply

In a Nov. 10 post on X, Glassnode said address reuse accounts for 25.8% of Bitcoin’s supply, including 11.6% held on exchanges. The exchange figure is part of the reuse total, not an additional category. Glassnode said moving coins exposed through reuse to a fresh address ends that exposure.

The firm distinguishes structural exposure, in which an output reveals a public key by design, from operational exposure linked to wallet use. Early pay-to-public-key outputs and Taproot outputs are structurally exposed, while address reuse can leave coins associated with a key already recorded on-chain. Reuse represents nearly 73% of the exposed supply, based on the latest figures; exchange-related exposure is roughly 45% of the reuse category.

A May 20 snapshot showed 6.04 million BTC, or 30.2% of issued supply, exposed. The latest total is 1.08 million BTC higher, and the share has risen by 5.2 percentage points. Glassnode’s measure does not identify compromised private keys or forecast when quantum attacks could become feasible.

The threat described in BIP 360 differs from brute-force guessing. Its authors say a sufficiently capable quantum computer running Shor’s algorithm could derive a private key from a visible public key. The draft, by Hunter Beast, Ethan Heilman and Isabel Foxen Duke, proposes pay-to-Merkle-root outputs through a soft fork, removing Taproot’s key-path spending option while keeping script-tree functionality. Its authors say post-quantum signatures may be needed to guard against faster attacks after a transaction reveals a key but before it is confirmed.

A separate draft, BIP 361, proposes migration away from legacy signatures once a post-quantum output type is available. It outlines restrictions on payments to vulnerable addresses around three years after activation, followed by tighter legacy-spending requirements two years later. Neither draft sets a migration deadline currently binding on holders.

In an October interview, Fireblocks Vice President of Research Michael Gutkin said exposure depends on address type and transaction history, not simply whether a holder is an exchange or an individual. He recommended sending new deposits and transaction change to fresh addresses and tracking exposed unspent outputs. In the US, NIST finalized three post-quantum standards in August 2024: ML-KEM for shared-secret establishment, and the digital-signature standards ML-DSA and SLH-DSA.