Coinbase board: 7M BTC exposed to future quantum attacks

Coinbase’s Independent Advisory Board on Quantum Computing and Blockchain published a report Thursday estimating roughly 7 million bitcoin are exposed to potential future quantum attacks. The board divided the exposure into two groups: about 1.7 million BTC in legacy pay-to-public-key (P2PK) addresses and roughly 5 million BTC at risk because their public keys have already been revealed through address reuse.

P2PK addresses reveal the public key as the address itself, so any funds remaining there would be vulnerable if a quantum computer can break current signature schemes. Many coins in those addresses are believed to be Satoshi-era holdings or wallets whose private keys are lost. The report cites the quantum-security firm Project Eleven in estimating the larger pool of roughly 5 million BTC tied to address reuse. That pool appears to belong mostly to active holders rather than permanently lost wallets, and the board says sizable amounts are in cold wallets linked to identifiable exchanges; the report does not name those exchanges.

The board laid out two main governance positions. One would set a deadline after which legacy signature schemes such as ECDSA and Schnorr are no longer accepted, which would leave coins that were not migrated permanently frozen. Proponents of a deadline contend that broken signature schemes would void cryptographic proof of ownership, that an uncontrolled release of long-lost coins could disrupt markets, and that freezing could stop sanctioned actors from seizing large holdings. The opposing position would enable post-quantum addresses while leaving the risk with individual owners. Opponents contend a network-level ban on legacy signatures would amount to confiscation, violate expectations of property rights, and unfairly penalize owners who cannot move funds because of imprisonment, death or temporary loss of access.

The report describes intermediate, technically compatible proposals. An “Hourglass” design would cap how many P2PK coins can move per block to limit a sudden supply shock. Draft BIP-361 would phase out legacy signatures after a set period but allow owners to prove control with a quantum-resistant zero-knowledge proof, an option available for wallets derived from seed phrases. Provable Address-Control Timestamps (PACTs) would let holders commit now to a future quantum-safe transfer without publicly moving funds onchain.

The board recommended that developers begin adding post-quantum signature support to wallets and software now, and that teams communicate clearer timelines and migration plans to users. The report notes that no existing quantum computer can break blockchain cryptography today and that the timing of any such capability is uncertain. It also states that both migration engineering and the governance debate will take years, so starting early is necessary to prepare.

Board members include Yehuda Lindell of Coinbase and Bar-Ilan University; Stanford professor Dan Boneh; UT Austin professor Scott Aaronson; Ethereum Foundation researcher Justin Drake; Sreeram Kannan of Eigen Labs and the University of Washington; and UCSB professor Dahlia Malkhi. The report references other industry plans to migrate to post-quantum cryptography, including a public timeline announced by another technology company setting a target for 2029.