Key Takeaways
- • Coinbase, which custodies roughly 5% of all Bitcoin in existence, is preparing its systems and advocating for the Bitcoin network's transition to post-quantum cryptography, drawing on more than 13 years of digital asset custody experience.
- • Coinbase is contributing engineering resources to the Bitcoin Security Consortium and argues that secure migration requires more than selecting a quantum-resistant signature scheme.
- • Coinbase's core requirements include MPC compatibility, deterministic cross-platform verification, flexible output designs such as P2MR (BIP-360) and P2TRv2, and an explicit pathway for holders who do not migrate before ECDSA/Schnorr spending is limited.
- • The company warns that proposals must address lost keys, inaccessible seeds, proof-system failures and expired rescue deadlines, and frames these as conditions for a practical and resilient implementation.
Summary
Coinbase, custodian to roughly 5% of all Bitcoin in existence, says it is actively preparing for the arrival of cryptographically relevant quantum computing. According to the company, its experience safeguarding digital assets at scale for more than 13 years now informs its approach to what it describes as an emerging threat to the Bitcoin network. Coinbase is contributing engineering resources and participating in the Bitcoin Security Consortium, and it argues that the community is beginning a complex, multi-year migration process.
Coinbase states that making Bitcoin secure against this threat "involves more than choosing a quantum-resistant digital signature scheme." The company emphasizes deterministic, cross-platform verification, so that candidate schemes function consistently across diverse computing environments. Compatibility with multi-party computation (MPC) signing is a key consideration for Coinbase and its institutional customers, who face constant cyberattack risk. The company notes that certain lattice-based approaches may integrate more readily with MPC, and it advocates including at least one MPC-compatible scheme among Bitcoin's post-quantum options.
On output design, Coinbase favors structures that accommodate multiple post-quantum signature systems without full overhauls, citing P2MR (BIP-360) and P2TRv2. It proposes decoupling the transaction output "container" from the signature scheme, using clear versioning and algorithm identifiers, and evaluating options such as PQ-only outputs for early adopters and 1-of-2 classical-plus-PQ hybrid constructions. Coinbase also supports commit/reveal mechanisms to limit public-key exposure during migration, and it has highlighted SHRINCS as a candidate worth evaluating while stressing the need to address signer state, recovery and implementation assurance for stateful schemes.
Coinbase's most distinctive concern concerns holders who do not migrate in time. The company proposes considering a mechanism for these users to move funds even after ECDSA/Schnorr spending is potentially limited or discontinued. It flags outputs with permanently exposed public keys, reused keys in hashed output types, dormant but legitimately controlled funds, and lost keys or inaccessible seeds as scenarios requiring attention. It also asks that proposals explicitly address cases where no recoverable secret exists, a proof system fails to scale, or a rescue deadline expires. Coinbase acknowledges there is no single solution that satisfies all constraints and says it aims to make its concerns visible so they can be weighed alongside those of other stakeholders.
Coinbase states that making Bitcoin secure against this threat "involves more than choosing a quantum-resistant digital signature scheme." The company emphasizes deterministic, cross-platform verification, so that candidate schemes function consistently across diverse computing environments. Compatibility with multi-party computation (MPC) signing is a key consideration for Coinbase and its institutional customers, who face constant cyberattack risk. The company notes that certain lattice-based approaches may integrate more readily with MPC, and it advocates including at least one MPC-compatible scheme among Bitcoin's post-quantum options.
On output design, Coinbase favors structures that accommodate multiple post-quantum signature systems without full overhauls, citing P2MR (BIP-360) and P2TRv2. It proposes decoupling the transaction output "container" from the signature scheme, using clear versioning and algorithm identifiers, and evaluating options such as PQ-only outputs for early adopters and 1-of-2 classical-plus-PQ hybrid constructions. Coinbase also supports commit/reveal mechanisms to limit public-key exposure during migration, and it has highlighted SHRINCS as a candidate worth evaluating while stressing the need to address signer state, recovery and implementation assurance for stateful schemes.
Coinbase's most distinctive concern concerns holders who do not migrate in time. The company proposes considering a mechanism for these users to move funds even after ECDSA/Schnorr spending is potentially limited or discontinued. It flags outputs with permanently exposed public keys, reused keys in hashed output types, dormant but legitimately controlled funds, and lost keys or inaccessible seeds as scenarios requiring attention. It also asks that proposals explicitly address cases where no recoverable secret exists, a proof system fails to scale, or a rescue deadline expires. Coinbase acknowledges there is no single solution that satisfies all constraints and says it aims to make its concerns visible so they can be weighed alongside those of other stakeholders.
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