Bitcoin Quantum Migration Could Take Years Warns Ledger CTO

Charles Guillemet, Chief Technology Officer at Ledger, has warned that migrating Bitcoin to a post-quantum signature scheme could take years. This warning comes after an evaluation of the SHRINCS proposal, a draft Bitcoin Improvement Proposal (BIP) that combines stateful signatures using Flexible XMSS and WOTS+C with a stateless fallback mechanism backed by SHA-256.

The current custody framework relies on digital signatures that would be compromised by a cryptographically relevant quantum computer. Guillemet noted that waiting for such hardware to emerge would represent an operational risk, given the extensive timeline required for research, testing, and network-wide deployment.

The SHRINCS draft specifies signature sizes ranging from 548 to 5,777 bytes, compared to the 64 to 72 bytes seen in current ECDSA and Schnorr schemes. Guillemet's analysis found that implementing this scheme introduces unprecedented operational requirements for custodial software and hardware.