risc0-ed25519-verified/README.md
mrwulf 82ee511277 Scalar layer complete: Montgomery reduction + full mul ported, scalarImplementation aggregate
Port of the dalek Montgomery stack against THIS fork's own extraction
(gen sections byte-identical, proofs recompiled from scratch here):
- Proofs/ScalarMulSpec.lean      - mul_internal: 9 exact schoolbook columns
- Proofs/ScalarMontSpec.lean     - part1/part2 exact-division rounds
  (LFACTOR*L0 = -1 mod 2^52), head/tail telescopes, mont_bound, tail walk
- Proofs/ScalarReduceSpec.lean   - montgomery_reduce main walk:
  scDenote r * 2^260 = Z in ZMod ell + 52-bit output bounds
- Proofs/ScalarFullMulSpec.lean  - mul = double Montgomery round through
  RR = R^2 mod ell; R cancelled as a unit; post: [mul a b] = [a]*[b]
- Proofs/ScalarMain.lean         - scalarImplementation aggregate (ScBnd
  interfaces; canonical inputs discharge the Montgomery bound)

sub_val_spec/add_val_spec posts strengthened with result-limb bounds.
check-scalar.sh: 9 proof files, 10 kernel audits, all exactly
[propext, Classical.choice, Quot.sound]. Button pressed fresh: green.
2026-07-03 21:46:39 +02:00

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# risc0-ed25519-verified
Formal verification of the ed25519 implementation in **risc0/curve25519-dalek (RISC Zero fork, v4.1.3)**, 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 │ Scalar52 ops correct mod
├──────────────────────────────┤
│ 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 | `scalarImplementation` (add ✅ sub ✅ mul ✅) | ✅ proven | `[propext, Classical.choice, Quot.sound]` |
| 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**: [risc0/curve25519-dalek](https://github.com/risc0/curve25519-dalek), commit `385adda`
- **Pinned/patched source**: [saymrwulf/risc0-curve25519-dalek-source](https://github.com/saymrwulf/risc0-curve25519-dalek-source), commit `2643444`
- **Patches**: minimal Aeneas-compatibility only (documented in the source repo)
- **Scope caveat**: this verifies the fork's pure-Rust `serial/u64` path. The RISC Zero zkVM accelerator/syscall path 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
```bash
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:
```bash
./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](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).