saymrwulf
422e91f270
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> |
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|---|---|---|
| verification | ||
| .gitignore | ||
| README.md | ||
| TRUSTED-BASE.md | ||
betrusted-ed25519-verified
Formal verification of the ed25519 implementation in betrusted-io/curve25519-dalek (Precursor/Xous fork, v4.1.2), built as a coherent proof pyramid in Lean 4 via the Charon/Aeneas transpilation pipeline:
┌──────────────────────────────┐
│ Signature (EdDSA verify) │ accepted ⇒ [8][S]B = [8]R + [8][k]A
├──────────────────────────────┤
│ Scalar arithmetic mod ℓ │ Scalar52 ops correct mod ℓ
├──────────────────────────────┤
│ Group law (twisted Edwards) │ point ops = complete addition law
├──────────────────────────────┤
│ Field 𝔽_p, p = 2²⁵⁵ − 19 │ FieldElement51 ops correct mod p
└──────────────────────────────┘
Every layer states its theorems about the actual Aeneas-transpiled Rust
code (never about a hand-written re-model), and every claim in the status
table below is backed by a compiled proof plus an axiom audit of the named
certificate. Files that do not compile under verification/check.sh are not
in this repository.
Layer status
| Layer | Certificate | Status | Axioms of certificate |
|---|---|---|---|
| Field 𝔽_p | fieldImplementation |
✅ proven | [propext, Classical.choice, Quot.sound] |
| Group law (Edwards) | edwardsImplementation |
✅ proven | [propext, Classical.choice, Quot.sound] |
| Scalar mod ℓ | add_val_spec ✅ sub_val_spec ✅ (aggregate planned) |
🔨 add+sub done · mul next | ⟦add⟧/⟦sub⟧ = +/− in ZMod ℓ proven against this fork's v4 two-loop masked-L sub; Montgomery mul next |
| Signature (EdDSA) | verifyEquation (planned) |
⏳ planned | — |
Status legend: ✅ proven & axiom-audited · ⏳ in progress · ❌ not started.
This table is updated only when verification/check.sh passes for the layer.
Source
- Upstream: betrusted-io/curve25519-dalek, commit
16e087a - Pinned/patched source: saymrwulf/betrusted-curve25519-dalek-source, commit
64ee8f0 - Patches: minimal Aeneas-compatibility only (documented in the source repo)
- Scope caveat: this verifies the fork's pure-Rust
serial/u64path. The Engine25519 hardware-accelerator path on Precursor is different code and is NOT covered by these proofs.
Toolchain (pinned)
| Component | Version |
|---|---|
| Aeneas | bf13c42e |
| Charon | 9dd7f23c |
| Lean | v4.30.0-rc2 |
| OCaml | 5.3.0 |
Reproducing
source ~/aeneas-toolchain/env.sh
cd verification
./extract.sh # Rust → LLBC → Lean (regenerates gen/)
./check.sh # compiles EVERY shipped file + axiom-audits EVERY certificate
The scalar layer has its own pair of buttons:
./extract-scalar.sh # regenerates gen/CurveScalar (Scalar52 limb arithmetic)
./check-scalar.sh # compiles the scalar gen + the proven scalar foundation
Trusted base
See TRUSTED-BASE.md for the complete list of assumptions (Lean kernel, mathlib, Charon/Aeneas semantics, external-function models, and — in the signature layer only — an opaque SHA-512 model).