mrwulf 2267e04d10 phase 2: FOURTH CERTIFICATE — hypertree layer walk (Algorithm 12) + de-plumbing ... fips205.ht_loop_eq (Proofs/HtSpec.lean): the extracted ht_verify_free_loop equals the explicit d-layer fold — at layer j: idx_leaf = idx_tree masked to h' bits (mask+cast), idx_tree >>= h', layer address j, tree address to the shifted index, node recomputed through xmss_pk_from_sig on the j-th XMSS signature. Pins the hypertree layer schedule; the final node == pk_root comparison sits one bind above in ht_verify_free (apex material). Exact cone: [propext, Classical.choice, Quot.sound, verify_mono.oracle.f, verify_mono.oracle.h, verify_mono.oracle.t_l] — kernel-3 plus exactly the three hash primitives the referenced WOTS+/XMSS machinery touches. THE LAYER'S OBSTRUCTION (one per layer, on pattern) was not the proof but the CONE: the first extraction of this loop carried Result-conversion plumbing (try_from/is_err/unwrap; transitively a Take iterator and the &u32 Sub instance) — all axioms, rightly rejected by the Phase-3 audit. Fixed at SOURCE level (fips205-source 6f6a9d6, 8 sites, semantics identical for every FIPS 205 parameter set, differential test re-run green), then re-extracted: the loop body is now straight-line and the proof is the plain chain/wots recipe (no branches; base case via loop.eq_1; step lemma closes by rfl; induction = bind_congr ×12). Also in this commit: - gen/ regenerated from the patched snapshot (loop bodies of the three prior certificates byte-identical modulo source line comments; all three proofs recompiled unchanged and re-audited green). - Dead-stub deletion (axiom-shadowing hygiene rule): the five obsoleted plumbing axioms + vestigial take.default removed from FunsExternal, the orphaned TryFromIntError type axiom removed from TypesExternal. The model's external surface is now: 5 SHA-2 oracles (the boundary), the Take iterator machinery used only by helpers::to_int (apex round's de-plumbing item), 3 zeroize blanket impls (never on the verify path), and the discharged-real u32 Step defs. - check.sh: PROOFS += HtSpec, CERTS += fips205.ht_loop_eq, audit import (self-test structure anchors untouched). README: four certificates + the de-plumbing record. Fidelity review at authorship (three-way): extracted body == Rust ht_verify_free (verbatim from upstream hypertree.rs, calls -> *_free) == FIPS 205 Algorithm 12, incl. mask-then-shift order and layer-then-tree address order. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>		2026-07-23 17:14:21 +02:00
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SlhVerify	phase 2: FOURTH CERTIFICATE — hypertree layer walk (Algorithm 12) + de-plumbing	2026-07-23 17:14:21 +02:00