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https://github.com/saymrwulf/risc0-ed25519-verified.git
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saymrwulf
49a68688c9
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>
73 lines
3.5 KiB
Markdown
73 lines
3.5 KiB
Markdown
# risc0-ed25519-verified
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Formal verification of the ed25519 implementation in **risc0/curve25519-dalek (RISC Zero fork, v4.1.3)**, 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 | `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 |
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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**: [risc0/curve25519-dalek](https://github.com/risc0/curve25519-dalek), commit `385adda`
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- **Pinned/patched source**: [saymrwulf/risc0-curve25519-dalek-source](https://github.com/saymrwulf/risc0-curve25519-dalek-source), commit `2643444`
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- **Patches**: minimal Aeneas-compatibility only (documented in the source repo)
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- **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.
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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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