dalek-ed25519-verified/TRUSTED-BASE.md

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# 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)**: FOUR apex-tier
certificates — `CurveFieldProofs.verify_accepts_iff` (byte apex:
accepted iff compress([s]·B [k]·A) = R byte-for-byte),
`verify_accepts_iff_point` (half-lift: R is the canonical encoding of
the recomputed point), `verify_accepts_iff_point_eq` (point equation:
canonically-encoded Q accepted iff Q equals the recomputed point), and
`verify_accepts_iff_decompress` (full lift: R decompresses to a valid
on-curve point that equals the recomputed point) — are each
`#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 theorems hold for
whatever bytes it produces; the SHA-512 implementation itself is NOT
verified. Zero curve, scalar, or backend axioms are in any of the four
cones. The constructive decompress theorem underneath the full lift
(`decompress_of_canonical`) carries the standard three axioms ONLY.
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.