What it covers. NIST recommendation approving two stateful hash-based signature schemes, LMS and XMSS, including their multi-tree variants. These schemes are considered resistant to attacks by quantum computers and are intended for specific uses such as firmware and software signing, where the number of signatures is limited and state can be managed carefully. It is part of NIST's post-quantum work but is not the general post-quantum standard.
In practice. The schemes are used where long-term signature security matters, in hardware or controlled environments that can manage signing state reliably. Organisations make sure a one-time key is never reused, which would break security. Evidence includes design records for signing infrastructure and controls on state management and backups.
Common gaps. Common gaps are underestimating the state management risk, especially around backups or cloning of signing systems.