extract.sh now opens crate::backend::serial::scalar_mul::vartime_double_base
(the other scalar_mul strategies stay opaque): non_adjacent_form (with its
loops), NafLookupTable5 (from/select), the curve-model helpers and
vartime_double_base::mul itself land in gen/CurveField - the same
namespace as the proven edwards operations, so the coming double-and-add
induction can consume EdDouble/EdAddProjNiels/EdConvert directly.
Zero sorries, zero external axioms (the pinned sources carry documented
compat refactors: single-assignment loop helpers, param-rooted while,
always-256-iterations, index-based LE load).
Full check.sh pressed fresh over the regenerated model: every existing
field and group-law certificate still green and axiom-clean - the scope
extension is purely additive.
The apex brick of the scalar layer: for any 64 bytes (the opaque SHA-512
digest), [from_bytes_wide bytes] = (LE 512-bit value) mod l, with
canonical 52-bit-bounded output. Composition: bytes_unpack_spec (8x8
loops) -> split_words_lo/hi_spec (exact div/mod per limb, disjoint ORs
as additions) -> wide_split_telescope (isolated omega) -> montgomery_mul
by R and RR (R cancels as a unit, RR restores it) -> the canonical add.
The two kernel-capacity walls found and crossed en route (control repo
FAILURES.md updated):
- a montgomery_mul inside any walk motive replays its 400-line body at
every kernel step (fix: named prefix functions in the pinned source);
- straight-line IndexMut closure chains make kernel defeq exponential in
depth (fix: struct-literal construction - the split halves now build
Scalar52([...]) directly). Full certificate: 77 s kernel-inclusive.
Regenerated gen (sources factor from_bytes_wide -> from_bytes_wide_parts
-> split_words_lo/hi; documented pure refactors, cargo-checked).
check-scalar.sh: 13 proof files, 13 kernel audits, all exactly
[propext, Classical.choice, Quot.sound]. Button pressed fresh: green.
Canonicity pass (the layer is now closed under its own preconditions):
- sub_val_spec post carries the exact value equation
(exists beta <= 1, scVal r + scVal b = scVal a + ell*beta, with the
underflow guard beta = 1 -> scVal a < scVal b)
- add/montgomery_reduce/mul/aggregate posts all carry scVal r < ell:
canonical inputs give canonical outputs everywhere. Needed because
from_bytes_wide (hash-to-scalar) feeds Montgomery outputs into add.
Hash-to-scalar foundation (toward Scalar::from_hash / EdDSA verify):
- extraction scope + from_bytes_wide (brings constants::R); regenerated gen
- source repos carry a documented Aeneas-compat patch: the bare
`hi[4] = words[7] >> 20` extracts ill-typed at pin bf13c42e; masked
(semantic no-op, words[7] >> 20 < 2^44)
- Proofs/ScalarWideSpec.lean: R constant lemmas (R = 2^260 mod ell,
witness 2^260 = R + 255*ell) and montgomery_mul_spec, the single
Montgomery round: [r]*2^260 = [a]*[b], canonical bounded output
check-scalar.sh: 10 proof files, 11 kernel audits, all exactly
[propext, Classical.choice, Quot.sound]. Button pressed fresh: green.
Transpile the Scalar52 limb backend (backend::serial::u64::scalar
add/sub/mul/square/montgomery_*) from Rust to Lean via Charon/Aeneas,
scoped at the function level to the iterator-free arithmetic core.
- verification/extract-scalar.sh: function-level Charon/Aeneas extraction
- verification/gen/CurveScalar/{Types,Funs}.lean: transpiled model (28 defs)
- verification/gen/CurveScalar/{TypesExternal,FunsExternal}.lean: hand-written
external models (subtle.Choice + 2 subtle fns; namespace = curve25519)
- verification/Proofs/ScalarDenote.lean: semantic foundation — Scalar52
denotation into ℤ/ℓℤ, limb-bound invariant, and L_val (the transpiled
constants::L denotes exactly the group order ℓ, kernel-checked)
- verification/check-scalar.sh: guarded compile of the four gen modules
plus the denotation foundation
check-scalar.sh passes: gen compiles; denotation + L = ℓ proven.
add/sub/mul remain in progress.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Extraction widened to backend::serial::curve_models + edwards (matching the
reference recipe; extra opaque: backend::scalar_fits_in_128_bits — a
post-reference NAF-path helper whose generated code trips an Aeneas
namespace-shadowing wart). Reference Ed* suite compiles UNCHANGED (same
crate namespace). All proofs pass; both certificates axiom-clean.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
