Bitcoin Exposure Measure Sorts Supply by Public-Key Visibility

Bitcoin's on-chain quantum-exposure measure sorts holdings by whether their controlling public keys are already visible on the blockchain, grouping supply by exposure to potential quantum attacks.

Five categories mark exposed supply: Taproot outputs; P2PK outputs attributed to Satoshi Nakamoto; other P2PK outputs; previously spent exchange addresses; and previously spent addresses elsewhere. The sixth category covers all remaining supply. The categories are mutually exclusive and together account for the total supply.

Each observation reflects supply at month-end, and the measure refreshes monthly. Exchange and Satoshi Nakamoto holdings are identified through entity clustering, so historical classifications can change when that clustering is updated.

Bitcoin output types reveal public keys in different ways, while the address-reuse categories track holdings at addresses that have already spent an output.