The Coinbase Independent Advisory Board on Quantum Computing and Blockchain estimates that 1.7 million Bitcoin (BTC) sit in an early output format that exposes public keys, creating a potential theft risk if quantum computers advance.
The Coinbase Independent Advisory Board on Quantum Computing and Blockchain put the June estimate at about 20,000 public keys in pay-to-public-key (P2PK) outputs. In that format, a public key is visible on the blockchain before the coins are spent.
The question for Bitcoin is how to protect those funds without cutting off their owners. The board said it could not determine how many people holding the older coins still have the private keys needed to move them. If the network eventually stops accepting older signatures, owners who have not moved their coins could lose the ability to spend them.
Bitcoin Improvement Proposal 361 (BIP-361) outlines a phased move away from signatures that a sufficiently powerful future quantum computer could compromise. It describes possible rescue methods for some owners after restrictions take effect. The proposal’s authors say no such method is currently known for P2PK outputs.
The proposal also measures exposure beyond P2PK. It says public keys had been revealed for more than 34% of all bitcoin as of March 1, 2026. Other output types can reveal keys when coins are spent, and later use of an address with an exposed key can put additional funds at risk. That broader March measure and the board’s June P2PK estimate describe different groups of coins.
A visible public key does not give an attacker control of the funds with current technology. The concern is that a future quantum computer might derive the corresponding private key and authorize a transfer.
BitGo introduced a risk score for exposed addresses and a process for moving funds in supported Bitcoin wallets in July. The company says those wallet controls cannot replace an upgrade to Bitcoin’s network rules.
BIP-361 remains a draft with no scheduled activation date. Its proposed stages would be timed from activation if the network adopts it.
