NIST approves stateful hash-based signatures in SP 800-208
29 OCTOBER 2020, GAITHERSBURG
NIST published Special Publication 800-208 on 29 October 2020, approving stateful hash-based signature schemes for federal use. The publication covers LMS and XMSS, together with their multi-tree variants HSS and XMSSMT. These schemes resist quantum attack, so they gave organizations an approved post-quantum signature option nearly four years before NIST finalized its main standards in 2024.
The schemes carry one important condition. A stateful scheme must never reuse a one-time signing key, so the signer has to track which keys it has already used. Reusing a key breaks the security of the signature. That requirement makes these schemes best suited to controlled environments where the signer can manage state reliably, rather than to general-purpose signing across many systems.
Firmware and software signing fit that profile well. Signing often happens in a controlled release process, where an organization can enforce state management and sign a bounded number of items over a product's life. For broader signature needs, the later ML-DSA and SLH-DSA standards usually fit better because they do not require state tracking.
Why it matters. SP 800-208 shows that an approved post-quantum signature option has existed since 2020 for the right use cases. Organizations that sign firmware or software can adopt stateful hash-based signatures today, provided they manage state carefully, and treat the 2024 standards as the general-purpose path. The choice between them depends on where and how the signing happens.