Coinbase lays out flexible designs as key priority for Bitcoin’s post-quantum migration

Coinbase has published a set of technical priorities for Bitcoin's post-quantum transition, urging the community to begin preparing for what it describes as a complex, multi-year process. The exchange, which holds roughly 5% of the total bitcoin supply, said it is already preparing its own systems for a post-quantum future and stressed that work should start well before any cryptographically relevant quantum computer (CRQC) emerges.

"We believe it is important to begin preparing well ahead of any CRQC announcement," Coinbase said. "Bitcoin consensus changes and ecosystem migrations can take years, so it is important that we begin this work now."

Design flexibility and staged protection

According to Coinbase, safeguarding the network involves more than choosing a quantum-resistant signature scheme. An ideal approach would protect both exposed and newly created funds, fit within Bitcoin's limited block space, preserve independent validation by full nodes, work with institutional custody systems, support ordinary wallets, and provide a credible path for coins that cannot or will not move.

At a high level, Coinbase favors separating the "container" from the signature scheme in post-quantum output designs, so components can be introduced, replaced or supplemented without a full redesign. It pointed to P2MR (BIP-360) and P2TRv2 as constructions that appear to offer this flexibility. The exchange also backs staged protection, allowing active wallets to use a post-quantum-capable or hybrid construction before final policy on legacy signatures is settled. One option it described was a 1-of-2 construction giving the same funds two spending paths — one authorized by a classical ECDSA or Schnorr key, the other by a post-quantum key.

On signature schemes, Coinbase said any support for stateful signatures should also include a stateless option, because stateful designs carry risks from state mismanagement that could lead to forgery. It added that multiparty computation (MPC) friendliness is important for institutional custody, and that at least one viable post-quantum option should have promising MPC compatibility.

"When implemented effectively, MPC can provide strong protection against key theft, and it is an important layer of defense for large organizations that face constant attacks on their infrastructure," the exchange said.

Regarding abandoned or inaccessible coins, Coinbase said those questions are difficult and deserve debate, but that the discussion can continue alongside technical work to add post-quantum signature support. "Coinbase believes that Bitcoin will continue to be the most trusted cryptocurrency in a post-quantum world," it said.