Bitcoin Quantum Upgrade Path Remains Unsettled After Coinbase Workshop

Coinbase is urging Bitcoin (BTC) developers and service providers to begin post-quantum planning early because protocol changes and wallet migrations can take years. The work is intended to prepare for a future quantum computer capable of threatening wallet signatures.

Coinbase’s Oct. 13 recommendations were presented as input to an open discussion, not a final company position. A transition would need to fit Bitcoin’s limited block space, remain practical for independent full nodes and work with ordinary and hardware wallets, institutional custody and multiparty-computation systems. The recommendations also address funds that users do not migrate promptly. Coinbase previously called for flexible Bitcoin quantum-security upgrades.

The concern centers on wallet signatures: a sufficiently powerful quantum computer could derive private keys from some publicly exposed keys and use them to authorize transactions. The Coinbase Independent Advisory Board on Quantum Computing and Blockchain assessed in April that no machine capable of threatening crypto existed at that time. The board considered such a machine likely to be at least a decade away, while allowing that it could arrive sooner. It said Bitcoin’s mining, hash functions and historical record were not meaningfully threatened.

The issue was discussed at a workshop hosted by Coinbase, Stanford and Localhost Research. Participants included Bitcoin developers, cryptographers, researchers, custodians and hardware-wallet experts. They did not reach consensus on an exact approach.

BIP 360, a draft proposal, would add a Pay-to-Merkle-Root output and remove Taproot’s key-path spend to reduce exposure to long-exposure quantum attacks. It does not introduce a post-quantum signature scheme and does not by itself protect against short-exposure attacks. Signature algorithms would need to be addressed separately.

One possible staged design would let the same funds be spent through either a current-signature path or a post-quantum path. Coinbase presented that as a possibility and left open how to handle wallets that migrate late, treating that question separately from the technical design work. The company’s recommendations did not settle on a final transition approach.