Bitcoin Migration May Take Years, Ledger CTO Warns

Bitcoin's migration to post-quantum signatures is not as straightforward as replacing its current cryptography, according to Ledger CTO Charles Guillemet. He stated that Bitcoin faces a 'migration problem,' not an immediate quantum crisis. The transition involves more than just selecting a new signature scheme; it also requires adapting wallets and protocol infrastructure to the new scheme and deciding how existing funds should be moved to quantum-resistant outputs.

Guillemet divided the transition into three problems: choosing a post-quantum signature scheme, updating Bitcoin wallets and protocol infrastructure, and handling existing coins that may have lost their keys or not been moved in years. The current SHRINCS draft proposal combines stateful signatures with a stateless fallback while relying on SHA-256 for security today.

The SHRINCS proposal has a significant impact on wallet security, as it requires every one-time signing key to be used only once, creating a new failure mode if the same slot is reused. Additionally, restoring a wallet from an older backup could restore an outdated counter, leading to potential fund theft risks.