Coinbase Braces Quantum-Safe Vaults for Every $BTC Flavor 🛡️

Coinbase is engineering post-quantum custody safeguards capable of accommodating whatever signature scheme Bitcoin and other networks ultimately adopt, according to Yehuda Lindell, the exchange's head of cryptography. Speaking on MARA Foundation TV with host Isabel Foxen Duke, Lindell said standards across blockchains are unlikely to converge on a single signing method, requiring custodians to support multiple outcomes. "It's unlikely that there will be a single signing scheme that everybody will use," Lindell said. "That means we have to be prepared and ready for the different outcomes on different blockchains."

Coinbase currently safeguards roughly $250 billion in assets on behalf of institutional clients including BlackRock. A central pillar of that custody stack is Multi-Party Computation (MPC), a cryptographic method in which distinct parties hold separate "shares" of a private key, allowing quorum-based signing without ever assembling a complete key on a single device. Unlike Bitcoin's native multi-signature setups, which enforce quorum rules on-chain, MPC operates off-chain.

The transition to post-quantum cryptography is testing that model. Lindell noted that "MPC-friendliness or non-MPC-friendliness makes a very big difference." Hash-based signatures, widely regarded as quantum-resistant due to their minimal underlying arithmetic structure, have historically been considered incompatible with MPC key-splitting techniques. Researchers including Dan Boneh have begun exploring possible workarounds in the recent "PRAWNS" paper, though the work remains experimental and no production-ready scheme has been demonstrated.

Concerns about hash-based compatibility have also surfaced among wallet developers, with Ledger CTO Charles Guillemet publicly flagging the issue. Lindell said Coinbase is researching fallback architectures for a scenario in which Bitcoin adopts a post-quantum scheme that cannot be supported by its existing MPC infrastructure, ensuring the firm's custody framework remains functional regardless of which cryptographic path the network selects.