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https://github.com/saymrwulf/dalek-ed25519-verified.git
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saymrwulf
ff1eea473d
New in Proofs/ScalarSubSpec.lean (all axiom-clean [propext, Classical.choice, Quot.sound], no sorry, no native_decide): - nat_and_mask52 / nat_shift52 / nat_shift63 : 52/63-bit ops -> %,/ - sub_step_arith : isolated per-limb borrow accounting (tiny ℕ context, correction-on-the-left so no truncated subtraction) — the METHOD-4 discipline that keeps 2^260-scale coefficients out of any one certificate - sub_loop_spec : the FULL 5-limb borrow chain of Scalar52::sub, unrolled via loop_step/range_next_*; wrapping_sub, 52-bit mask store, borrow-out bit. This is the loop unroll that blocked the earlier attempt. - csel_step : step-spec for the subtle conditional_select (faithful model) - cond_add_l_zero_spec / cond_add_l_one_spec : BOTH cases of conditional add-of-L, full carry chains; the condition-1 case steps the addend as a clean value so the index_mut write-back matches sub_loop's pattern - sub_telescope / add_telescope : the 2^52i-weighted value telescopes to 2^260, discharged by omega (no kernel-capacity blowup) check-scalar.sh: ScalarSubSpec added to the compile manifest; Phase-3 axiom audit extended to sub_loop_spec + cond_add_l_one_spec (3/3 clean). Full button green. Honest boundary: top-level sub_val_spec (⟦sub a b⟧ = ⟦a⟧-⟦b⟧ in ZMod ℓ) is documented as remaining — every lemma it needs is proven; what's left is the Aeneas binding-arity for destructuring sub_loop_spec's pair-valued multi-existential postcondition inside the do-block, a mechanical not a mathematical gap. No sorry shipped (Invariants H1/H4). Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
81 lines
3.9 KiB
Markdown
81 lines
3.9 KiB
Markdown
# dalek-ed25519-verified
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Formal verification of the ed25519 implementation in **dalek-cryptography/curve25519-dalek (upstream, v5.0.0-rc.1)**, built as a
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coherent proof pyramid in Lean 4 via the Charon/Aeneas transpilation pipeline:
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```
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┌──────────────────────────────┐
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│ Signature (EdDSA verify) │ accepted ⇒ [8][S]B = [8]R + [8][k]A
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├──────────────────────────────┤
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│ Scalar arithmetic mod ℓ │ Scalar52 ops correct mod ℓ
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├──────────────────────────────┤
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│ Group law (twisted Edwards) │ point ops = complete addition law
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├──────────────────────────────┤
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│ Field 𝔽_p, p = 2²⁵⁵ − 19 │ FieldElement51 ops correct mod p
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└──────────────────────────────┘
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```
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Every layer states its theorems about the **actual Aeneas-transpiled Rust
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code** (never about a hand-written re-model), and every claim in the status
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table below is backed by a compiled proof plus an axiom audit of the named
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certificate. Files that do not compile under `verification/check.sh` are not
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in this repository.
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## Layer status
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| Layer | Certificate | Status | Axioms of certificate |
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|-------|-------------|--------|-----------------------|
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| Field 𝔽_p | `fieldImplementation` | ✅ proven | `[propext, Classical.choice, Quot.sound]` |
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| Group law (Edwards) | `edwardsImplementation` | ✅ proven | `[propext, Classical.choice, Quot.sound]` |
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| Scalar mod ℓ | `scalarImplementation` (planned; `L_val`, `sub_loop_spec`, `cond_add_l_*_spec` proven) | 🔨 foundation+sub | denotation + L=ℓ + sub borrow/carry chains proven; sub value-assembly & mul in progress |
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| Signature (EdDSA) | `verifyEquation` (planned) | ⏳ planned | — |
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Status legend: ✅ proven & axiom-audited · ⏳ in progress · ❌ not started.
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This table is updated only when `verification/check.sh` passes for the layer.
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## Source
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- **Upstream**: [dalek-cryptography/curve25519-dalek](https://github.com/dalek-cryptography/curve25519-dalek), commit `4cf8db2`
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- **Pinned/patched source**: [saymrwulf/curve25519-dalek-source](https://github.com/saymrwulf/curve25519-dalek-source), commit `135ed70`
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- **Patches**: minimal Aeneas-compatibility only (documented in the source repo)
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- Verified backend: `backend/serial/u64` (`FieldElement51`, `Scalar52`). SIMD/AVX backends are out of scope (marked opaque).
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## Toolchain (pinned)
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| Component | Version |
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|-----------|---------|
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| Aeneas | `bf13c42e` |
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| Charon | `9dd7f23c` |
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| Lean | `v4.30.0-rc2` |
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| OCaml | `5.3.0` |
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## Reproducing
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```bash
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source ~/aeneas-toolchain/env.sh
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cd verification
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./extract.sh # Rust → LLBC → Lean (regenerates gen/)
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./check.sh # compiles EVERY shipped file + axiom-audits EVERY certificate
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```
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The scalar layer has its own pair of buttons:
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```bash
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./extract-scalar.sh # regenerates gen/CurveScalar (Scalar52 limb arithmetic)
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./check-scalar.sh # compiles the scalar gen + the proven scalar foundation
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```
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## Trusted base
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See [TRUSTED-BASE.md](TRUSTED-BASE.md) for the complete list of assumptions
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(Lean kernel, mathlib, Charon/Aeneas semantics, external-function models,
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and — in the signature layer only — an opaque SHA-512 model).
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## Provenance
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Proof engineering in this repository builds on the verification methodology
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and proof architecture of
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[PlanetMacro/ed25519-verificationtest](https://github.com/PlanetMacro/ed25519-verificationtest)
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(the reference solution). All proofs here are checked against **this fork's
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own extracted code**; nothing is claimed that the check script does not compile.
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