Coinbase is preparing custody infrastructure to protect its assets in a post-quantum computing era, according to the exchange's Head of Cryptography Yehuda Lindell. The company manages approximately $250 billion in assets for institutional clients including BlackRock.
The challenge stems from uncertainty around which post-quantum signature scheme Bitcoin will ultimately adopt. Lindell noted that multiple blockchains may choose different standards, requiring Coinbase to build systems capable of supporting various technical approaches.
The Multi-Party Computation Problem
Currently, Coinbase relies on Multi-Party Computation (MPC) for custody security. MPC allows different parties to hold distinct shares of a private key, enabling transaction signing without exposing the complete key in any single location. This distributed approach eliminates single points of failure.
However, not all post-quantum signature schemes are "MPC-friendly." Hash-based signatures, which are considered secure against quantum threats, lack the underlying mathematical structure necessary for traditional key-splitting. While this mathematical simplicity is precisely what makes hash-based signatures quantum-resistant, it also creates challenges for MPC infrastructure.
Cryptographers are actively researching solutions, though work in this area remains experimental.
Hardware Security Module Fallback
If Bitcoin adopts a post-quantum scheme incompatible with MPC, Coinbase is exploring a fallback architecture using programmable Hardware Security Modules (HSMs)—encrypted key storage systems located within physically secure data centers.
Under this approach, private keys would be encrypted with post-quantum cryptography and only assembled within the HSM's protected environment. While assembling a complete key in one location is theoretically less secure than distributed MPC, HSMs provide strong protection through physical side-channel defenses and strict code-upload controls.
Coinbase is designing its custody architecture to remain agnostic regarding which post-quantum standard Bitcoin ultimately selects, allowing the exchange to adapt as the industry moves forward.
