The workspace reserves a pq-signatures Cargo feature flag for future
stateful hash-based signatures (XMSS per RFC 8391, LMS/HSS per RFC 8554).
Status: No XMSS or LMS implementation is wired in this repository yet. The feature flag is a no-op placeholder for forward compatibility.
Policy: When an implementation is added, it must ship with an independent audit of the chosen Rust crates, documented test vectors, and clear warnings in release notes until the audit is complete.
Do not enable pq-signatures in production firmware until this document is
updated with audit identifiers and test coverage summaries.
Stateful hash signatures (XMSS / LMS): When an implementation lands, private state (for example chain / index position) must be updated atomically in non-volatile storage. On Baochip-1x the natural store is on-chip RRAM (4,194,304 bytes total — see RRAM_LAYOUT.md). No reserved RRAM slots or wear model for such state exist in this repository yet; the layout must be defined with boot and vault integrators before production use.