Coinbase is developing post-quantum custody measures to safeguard Bitcoin against potential quantum computing threats, focusing on flexibility and security.
Coinbase's Post-Quantum Custody Strategy
In response to the anticipated risks posed by quantum computing to Bitcoin's security, Coinbase is developing adaptive custody measures to protect digital assets, as detailed by Yehuda Lindell, the company's Head of Cryptography.
Coinbase manages around $250 billion in assets for major clients, including BlackRock, and has dedicated years to refining its custody processes. As Bitcoin enters a post-quantum era, the company is preparing for challenges that may arise with existing Multi-Party Computation (MPC) methods, which rely on divided keys to ensure security.
Challenges with Multi-Party Computation
MPC allows multiple parties to hold shares of a private key, facilitating secure transactions without exposing the entire key. However, Lindell warns that many post-quantum signature schemes may not be compatible with this technology. Certain hash-based signatures, while secure against quantum attacks, might lack the necessary structure for effective key-splitting, complicating the development of MPC-compatible systems.
Despite these challenges, leading cryptographers are exploring solutions, but the feasibility of integrating MPC with hash-based signatures remains uncertain. Concerns have also been raised by wallet developers, including those from Ledger.
Fallback Hardware Solutions
If Bitcoin adopts a post-quantum signature scheme incompatible with MPC, Coinbase is considering a fallback solution that utilizes programmable Hardware Security Modules (HSMs). These secure environments would store encrypted keys, assembled only within the HSM, providing robust protection despite the theoretical risks of temporarily housing complete keys in one location.
Lindell expressed confidence in this approach, citing strong physical defenses and strict access controls. He emphasized the need for Coinbase's custody framework to be versatile, adapting to any future signing schemes Bitcoin may adopt.
While the timeline for implementing these post-quantum security measures is still undefined, Lindell is optimistic about the company's ability to accommodate various blockchain methods, stating, "I can support anything. We won't be concerned that some blockchain will choose a method that we cannot accommodate."
