This v4.1.x fork implements Scalar52::sub with TWO loops (loop0 = borrow
chain; loop1 adds L &&& underflow_mask — the arithmetic-mask constant-time
conditional), a genuinely different code path from upstream v5's
subtle-based conditional_add_l. Verified per R2 against this fork's own gen:
- sub_loop_spec (= loop0): borrow chain, verbatim technique from dalek
- sub_loop1_zero_spec / sub_loop1_one_spec: the masked-L add, both mask
values (0 / 2^64-1), full carry chains
- sub_val_spec: denote(sub a b) = denote a - denote b in ZMod l; the
underflow mask um = ((borrow>>>63) XOR 1) - 1 resolved per case
- add_loop_spec + add_val_spec: denote(add a b) = denote a + denote b
(v4 add_loop extracts token-identical to v5; composition through this
fork's own sub_val_spec)
check-scalar.sh: full manifest, 5/5 kernel axiom audit
[propext, Classical.choice, Quot.sound], green at 300-400s/4096MB.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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.
This fork (v4.1.3) inlines a local `black_box` (a volatile read used as an
optimization barrier) inside Scalar52::sub; charon cannot translate the
`&raw const` it lowers to, so it is marked --opaque and modeled below.
- verification/gen/CurveScalar/{Types,Funs}.lean: transpiled model (27 defs)
- verification/gen/CurveScalar/FunsExternal.lean: hand-written model of
Scalar52::sub::black_box as the identity on u64 (a volatile read returns
the value written; the qualifier is only an optimization barrier).
TypesExternal.lean is decl-free — this fork pulls in no external types
(unlike v5 dalek, which routes sub through subtle::Choice).
- 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 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>
Ported from the locally verified Hermes working copy; FeQ and Square2Spec
(dead files in the published replica) now compile and are in the check
manifest. Basic.lean (never compiled under v4 Aeneas) removed rather than
shipped dead.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
