Formally verified ed25519 (risc0 curve25519-dalek fork v4.1.3): field + complete Edwards addition law proven in Lean 4 via Charon/Aeneas; axiom-audited certificates
Find a file
mrwulf cc571bf163 verification: derive lift dependencies instead of hand-keeping them
Round-9 swept all ten instruments per fork instead of only the two buttons,
and found selftest-axgate.sh red in all four. Root cause, identical to the
KERNLOG defect fixed the day before: a self-test lifts one phase out of
check.sh and supplies its variables from a HAND-WRITTEN preamble, and the
phase later grew a dependency nobody told the preamble about.

Phase 2b stopped globbing Proofs/*.olean and started reading $PROOFS by
membership. Bash does not error on an unset array under `set -u` — it
expands to nothing — so the gate silently received

    expected := [".olean"]

one entry with an empty name, and rejected the baseline via its own
fail-closed absence check. Exit code right, reason wrong.

  · lift-guard.sh (new, pinned): derives every variable the lifted payload
    reads, subtracts what the driver defines, and fails AT LIFT TIME naming
    the remainder. Wired into all five lifting self-tests; selftest-shapes.sh
    drops its inline copy. One implementation, not five, since drifting out
    of sync is the entire failure mode.

  · selftest-axgate.sh: lifts PROOFS verbatim, and its case 2 now poisons a
    MANIFESTED leaf module rather than adding a stray file. The stray-file
    attack was a no-op against membership semantics — that is the dead-file
    gate's job, proven by selftest-harness case 8 — and it is also the
    weaker attack, since adding files to Proofs/ must clear a gate that
    editing an already-manifested module does not.

  · Phase 2c's accounting identity moves behind its own marker with its own
    ACCTFAIL verdict, so the phase is liftable by construction rather than
    by a self-test knowing where to stop. Truncating the lift range alone
    would have dropped Phase 2c's own verdict and left the test unable to fail.

  · The other four lifting self-tests assert on the PAYLOAD rather than the
    assembled driver, so a marker in the preamble cannot satisfy a check
    meant to prove the lift landed.

Certified: 8/8 self-tests green in all four forks (~212 assertions, none
failing); check.sh bytes unchanged and still matching the pin written before
the 3h08m round-9 sweep, whose 36 GREEN button rows therefore stand.
--audit-only re-run against the new HARNESS.sha256 in every fork.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
2026-08-02 13:07:28 +02:00
verification verification: derive lift dependencies instead of hand-keeping them 2026-08-02 13:07:28 +02:00
.gitignore Round-7 F1: make model/template correspondence SEMANTIC, and fail closed 2026-08-02 02:24:15 +02:00
README.md Coherence pass 4 (the closing pass): 4-tier apex documentation + hygiene 2026-07-06 04:01:18 +02:00
TRUSTED-BASE.md P2-c: classify and pin the extraction boundary 2026-07-31 17:53:31 +02:00

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 ⇔ decompress(R) = [k](A)+[s]B
        ├──────────────────────────────┤
        │  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) verify_accepts_iffverify_accepts_iff_decompress (4 tiers) proven (phases 1+2) standard three + the button-enforced SHA-512/wire-format boundary — see The signature apex

Status legend: proven & axiom-audited · in progress · not started. This table is updated only when verification/check.sh passes for the layer.

The signature apex (phases 1 and 2)

The apex certificate CurveFieldProofs.verify_accepts_iff is the literal EdDSA acceptance criterion, proven about the extracted verifier:

For a signature that parses, the verifier returns Ok(()) iff the recomputed compressed point compress([s]·B [k]·A) equals the signature's R, byte-for-byte — where k is whatever scalar the opaque SHA-512 oracle produces from (R, A, msg).

The recomputation runs entirely through the proven model: the vendored ed25519-dalek verify glue is extracted as gen/CurveSig, whose hand-maintained externals import gen/CurveField — every curve and scalar call resolves by fully-qualified name to a proven definition. Only SHA-512 (a single monomorphic sha512_hash3(R, A, m) oracle — this fork's sha2-0.10 stack makes the incremental-hasher types untranslatable) and the wire-format types stay opaque.

check.sh has a dedicated audit phase (Phase 3b) that fails the build unless each apex-tier certificate's axiom cone is exactly

[propext, Classical.choice, Quot.sound] + {ed25519.Signature, verifying.sha512_hash3, ed25519.Signature.to_bytes, signature.error.Error, signature.error.Error.new}

— i.e. the three Lean foundations plus the documented SHA-512/wire-format boundary. Zero curve, scalar, or backend axioms. The companion certificate verify_loop_full (the 32-byte comparison loop computes array equality) carries the standard three axioms only.

Phase 2 (complete): the point-level lift. Phase 3b enforces the SAME axiom boundary on three further tiers that lift the byte equation to points:

Tier Certificate Statement
half-lift verify_accepts_iff_point accepted ⇔ R = the canonical encoding of [k]·(A) + [s]·B (compress semantics + as_bytes canonicity + hash-to-scalar, recompute chain inverted)
point equation verify_accepts_iff_point_eq for any valid on-curve Q canonically encoded by R: accepted ⇔ Q = [k]·(A) + [s]·B as points (encoding-injectivity: d non-square + parity root-selection)
full lift verify_accepts_iff_decompress R decompresses to a valid on-curve Pt, and accepted ⇔ Pt = [k]·(A) + [s]·B — the constructive capstone

The full lift runs through the extracted CompressedEdwardsY::decompress itself, proven end-to-end: from_bytes parses the y-residue exactly below bit 255 (from_bytes_spec), sqrt_ratio_i returns the even square root of (y²1)/(dy²+1) (sqrt_ratio_i_sq_spec, Fermat-exponent square root), and the sign bit selects the x-parity (decompress_of_canonical, standard three axioms). Byte comparison ↔ encoding equality ↔ point equality ↔ decompressed-point equality: every link is machine-checked over the extracted code, and check.sh fails the build if any of the four tiers' cones deviates from the boundary above.

Source

  • Upstream: risc0/curve25519-dalek, commit 385adda
  • Pinned/patched source: saymrwulf/risc0-curve25519-dalek-source, commit d58065f (adds the decompress step_2 negate-then-assign patch)
  • 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

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 gen model is ONE merged universe (gen/CurveField: field + curve + scalar + the verify path's reachable code), regenerated in full by extract.sh. The scalar layer keeps its own check button:

./check-scalar.sh     # compiles the merged gen + all scalar proofs (add, sub,
                      # Montgomery mul, byte-parsing) and kernel-audits the
                      # scalar certificates, incl. the scalarImplementation
                      # aggregate

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).