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fips205-slhdsa-verified/TRUSTED-BASE.md
mrwulf 45a2f65a2d review round 4: bind the cert set, statements, and model bytes (F1/F2/F3) 
The third reviewer demonstrated that the round-2 in-Lean exact-cone audit,
though sound for LISTED certs, left three fail-opens OUTSIDE the cone check —
and made check.sh print ALL GREEN over a repo proving False. All closed; no
theorem, proof, or fold changed (the 11 cones are unchanged).

F1 — the audited SET was unbound. Audit.lean now (a) enumerates EVERY theorem
defined in the eight certificate modules and requires each cone ⊆ boundary, so
an un-manifested `theorem _ : False := cheat _` fails regardless of naming
(this is the exact exploit the reviewer used); and (b) prints a MANIFEST
fingerprint over the whole committed manifest, which check.sh binds to — so
deleting/swapping a cert row fails outside Lean too.

F2 — only cones were bound, not statements. Each cert now also carries the
structural fingerprint (Expr.hash) of its elaborated type; a statement gutted
to a tautology of the same cone changes the fingerprint and fails.

F3 — the gen/ model bytes were unbound. New check.sh Phase 0 sha256-pins all
four gen/SlhVerify/*.lean (incl. the two hand-maintained *External files, now
hashed in PROVENANCE.json) BEFORE compiling; a hand-edited model fails first.

F4/F5 — docs. README cone diagram now roots honestly at slh_verify_internal
and states the pure/prehash domain-separator byte, the ctx>255 check, M'
assembly, and deserialization are ABOVE the root and uncovered (new
TRUSTED-BASE item 10). The false "rules out a wrong ADRS field" claim is
corrected in README + ChainSpec (a transliteration makes the field visible,
not excluded).

check-selftest.sh: eight attacks, all rejected (dead file; extra axiom;
dropped oracle; vanished cert; un-manifested False theorem; gutted statement;
hand-edited model; deleted manifest row). Full transcript + green check.sh in
verification/RECORDED-RUN.md.

Standing limit unchanged and disclosed: an audit cannot defend against an
author who edits the manifest AND check.sh AND the proofs together; the
consumer defense is the pinned commit reviewed at the pin.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
2026-07-27 19:47:39 +02:00

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TRUSTED-BASE — what the certificates do NOT cover

Eleven certificates over the extracted verify_mono model are now proven (verification/check.sh green; the apex is fips205.slh_verify_128s_accepts_iff). This file states what those certificates deliberately do NOT establish; it is maintained as the campaign proceeds and is part of every claim.

  1. The five verify-path hash oracles. h_msg, f, h, t_l, t_len (SLH-DSA-SHA2-128s instantiations over SHA-256; prf/prf_msg are sign-side only and do not appear in the cone) are modeled as opaque functions with assumed functional behavior. Their correctness against FIPS 180-4 is NOT proven here — the same standing boundary as SHA-512 in the ed25519 apex. A collision or misimplementation inside the hash layer is invisible to these certificates.
  2. Signing and key generation. Out of extraction scope entirely. A verified verify path says nothing about the safety of signature or key production (including randomness).
  3. The transpilation pair. Charon and Aeneas (pinned versions in the toolchain) are trusted to preserve semantics from Rust (MIR) to the Lean model. Divergence between rustc's semantics and the extracted model is trusted base.
  4. The Lean kernel and its three axioms (propext, Classical.choice, Quot.sound).
  5. Build correspondence. No reproducible-builds claim: the proof is about the pinned source, not about any particular compiled binary (the estate's R5 gap, stated everywhere it matters).
  6. Parameter-set scope. Claims will bind SLH-DSA-SHA2-128s only; other parameter sets are unverified until separately extracted and proven (R2).
  7. Aeneas-compat + de-plumbing patch surface. The fn-pointer-to-named- oracle rewrite in fips205-source (phase 1) and the two de-plumbing rounds (index-loop rewrites of the iterator adapters on the verify path, de-plumbing round 2 at bea1051; current snapshot head 797b4ef) are part of the verified surface: the certificates cover the patched verify path, and the patch commits are the auditable delta from upstream 30bac08. Each rewrite's equivalence to upstream is argued in its commit and checked, for SHA2-128s, by the snapshot differential test — it is not itself machine-checked.
  8. The base_2b inner loop. helpers.base_2b_loop0_loop0 (which determines the FORS indices and WOTS digits) is threaded opaquely and has no certificate; a defect there could change the recomputed root while all eleven theorems still hold.
  9. The deployed generic verifier. The proved subject is the private verify_mono facade. The bridge to upstream's generic pk.verify() is the finite in-snapshot differential test, not a machine-checked refinement.
  10. Everything above the extraction root. The root is verify_mono::slh_verify_128s = slh_verify_internal_free(M′, sig, pk), which takes the message-digest input M′ as an argument. The code in slh_verify/verify (src/lib.rs) that runs before this root is NOT covered by any certificate: the assembly of M′; the pure-vs-prehash domain-separator byte (0u8 for verify vs 1u8 for hash_verify — the whole cross-variant domain separation); the FIPS-205 ctx.len() > 255 bound; and signature/public-key deserialization. The certificates say nothing about this input handling — a defect there (e.g. a wrong separator byte) would be outside every proof.