Bitcoin and Ethereum Diverge on Post-Quantum Cryptography Adoption

NIST's post-quantum cryptography standards have significant implications for Bitcoin and Ethereum. Two digital signature schemes, ML-DSA and SLH-DSA, are at the center of this discussion. The former is a lattice-based approach that relies on computational hardness in high-dimensional space, while the latter is built on hash functions that have been battle-tested for decades.

NIST published these standards in August 2024, but their adoption has not been uniform across industries. Bitcoin and Ethereum are leaning towards SLH-DSA due to its conservative approach, which relies on trusted hash functions rather than novel mathematical assumptions. This choice is driven by the need for efficiency and scalability.

The tradeoff between security and performance is a key consideration in this decision. While ML-DSA has become the go-to choice in other sectors, SLH-DSA's larger signatures pose challenges when it comes to storage costs, bandwidth, and economic math. Ethereum researchers are exploring optimized Sphincs+ variants specifically designed to make verification more tractable within the Ethereum Virtual Machine.

For Ledger, this is a pressing issue as their security team is actively working on integrating post-quantum cryptography into their hardware wallet firmware. They plan to ship support for both ML-KEM and ML-DSA by the end of June 2026, representing a reasonably complete post-quantum security posture.