# Trusted base

What you must believe for the theorems in this repository to transfer to the
running Rust code. Everything else is machine-checked.

1. **Lean 4 kernel** (v4.30.0-rc2) and its three foundational axioms
   `[propext, Classical.choice, Quot.sound]`. Every certificate is
   `#print axioms`-audited against exactly this list.
2. **mathlib** (prebuilt oleans fetched by `lake exe cache get`).
3. **Charon + Aeneas** (pinned `9dd7f23c` / `bf13c42e`): the translation
   from Rust MIR to the Lean model is assumed faithful. The generated
   `gen/` files are never edited (comments only); proofs are stated ABOUT them.
4. **External-function models** (`gen/*/FunsExternal.lean`): Rust items that
   Aeneas cannot translate (constant-time `subtle` primitives, iterator
   plumbing, formatting) are axiomatized as opaque symbols. The axiom audit
   proves none of these axioms enters the dependency cone of any certificate,
   except where a model is explicitly listed below.
5. **The signature-apex boundary (signature layer only)**: the apex
   certificate `CurveFieldProofs.verify_accepts_iff` ("the verifier accepts
   iff compress([s]·B − [k]·A) = R byte-for-byte") is `#print axioms`-audited
   by check.sh Phase 3b against EXACTLY the standard three plus this
   documented set, and the build fails on any deviation:
   `ed25519.Signature` (wire-format type), the three SHA-512 wrapper
   oracles `verifying.sha512_new/update/finalize_bytes` (+ the opaque
   `sha2.Sha512` state type), `ed25519.Signature.to_bytes`, and
   `signature.error.Error`/`Error.new` (opaque error type). The hash is an
   oracle with no algebraic properties assumed — the theorem holds for
   whatever bytes it produces; the SHA-512 implementation itself is NOT
   verified. Zero curve, scalar, or backend axioms are in the cone.
6. **Compilation of Rust to machine code** (rustc backend) is out of scope,
   as is side-channel behaviour (timing, speculation). The proofs are about
   functional correctness at the MIR/LLBC level.