Coinbase plans post‑quantum custody for $250 billion in assets

Coinbase is building a post‑quantum custody system that can protect the roughly $250 billion it holds for institutional clients such as BlackRock. The design aims to work with any future Bitcoin signature scheme, acknowledging that the blockchain may adopt multiple, potentially non‑MPC‑friendly, post‑quantum algorithms.

Why a new approach is needed

Current custody relies on Multi‑Party Computation (MPC), where a private key is split into shares held by different parties. MPC works well with today’s elliptic‑curve signatures but may not be compatible with many post‑quantum schemes, especially hash‑based signatures that lack the arithmetic structure required for key‑splitting.

Exploring fallback hardware

If Bitcoin selects a post‑quantum scheme that cannot be used with MPC, Coinbase is researching a fallback that uses programmable Hardware Security Modules (HSMs). In this model, private keys would be encrypted with post‑quantum cryptography and only assembled inside a physically secured HSM, providing strong side‑channel protection.

Preparing for multiple outcomes

Yehuda Lindell, Coinbase’s head of cryptography, emphasized that the company expects a variety of possible signing standards across blockchains. The goal is to have a custody architecture that is agnostic to the specific algorithm, allowing support for any future upgrade without major redesign.

Timeline and next steps

Coinbase has not disclosed a completion date for the post‑quantum safeguards. Lindell indicated that once the system is ready, the exchange will be able to support any signing scheme without fearing incompatibility.