Coinbase wants to move now
Such efforts need to begin immediately, largely because Bitcoin’s decentralized design, often praised as an advantage over centralized institutions, also makes implementing changes difficult.
As the exchange put it, “Bitcoin consensus changes, and ecosystem migrations can take years.” That’s why work needs to start “well ahead of any CRQC announcement.”
Bitcoin developers are already considering proposals to build quantum defenses.
Measures proposed by Coinbase
Separating the “container” from the signature
In simple terms, Bitcoin should be designed such that its transaction format can support new post-quantum signature types without needing to rebuild the whole system. That would make it easier to add, replace or combine quantum-resistant signatures over time. Two proposals, P2MR (BIP-360) and P2TRv2, appear to offer this kind of flexibility, Coinbase said.
Staged protection
Coinbase supports an approach that lets active wallets start using quantum-resistant, or hybrid, signatures before Bitcoin finalises its rules for older signature types. One possible transition would be a “1-of-2” setup: the same bitcoin could be spent using either a traditional ECDSA or Schnorr key, or a post-quantum key. This would let users protect their funds earlier, without forcing everyone to switch at once or risking a sudden loss of access.
Use of state
Some post-quantum signature schemes need the wallet to keep track of information, called “state,” after each signature. These schemes use many one-time signing keys, and the wallet must remember which ones have already been used so it never reuses one. If a wallet restores from an old backup or fails to save that record, it could accidentally reuse a key.
