Coinbase is designing a post-quantum custody architecture for roughly $250 billion in institutional assets, including assets it holds for BlackRock, as it prepares for Bitcoin and other networks to adopt potentially different quantum-resistant signature schemes. Its current institutional system uses Multi-Party Computation (MPC), which divides private-key shares among parties so no single machine holds the full key. Yehuda Lindell, Coinbase's Head of Cryptography, said hash-based signatures are among the post-quantum options that may not work with MPC because they lack the required arithmetic structure. Coinbase is therefore considering programmable Hardware Security Modules (HSMs) in private data centers, where post-quantum-encrypted keys would be assembled only inside hardened devices if an MPC-incompatible scheme is adopted. Coinbase custodies 81% of the $140 billion held in US crypto ETFs and in July 2026 joined eight firms in a $15 million, three-year Bitcoin Security Consortium focused on open-source security work, with quantum risk a priority.