## ADDED Requirements

### Requirement: Universal curve primitive surface

`@suaveplan/crypto-curve` SHALL expose a stable public API for the curves listed below, independent of the underlying implementation source.

#### Scenario: Curves available

- **WHEN** a consumer imports from `@suaveplan/crypto-curve`
- **THEN** `secp256k1`, `ed25519`, `x25519`, `p256` are exported
- **AND** each curve exposes the operations it supports: `getPublicKey`, `sign`, `verify`, `getSharedSecret` (ECDH), `utils.randomPrivateKey`, as appropriate
- **AND** each curve is also exported from the subpath `@suaveplan/crypto-curve/<id>` for tree-shaking

### Requirement: Per-primitive replaceability

Every curve in `@suaveplan/crypto-curve` SHALL have both a vendor-forked `noble` implementation and a `native` implementation slot, selected per-primitive at build time via the root `crypto.config.ts`.

#### Scenario: Every curve has both impl files

- **WHEN** the package is inspected
- **THEN** every curve id has both `src/primitives/<id>/impl/<id>.noble.ts` and `src/primitives/<id>/impl/<id>.native.ts`
- **AND** the `native.ts` file is either a working implementation or a stub that throws `PrimitiveNotImplemented('<id>')`

### Requirement: Vendored noble source (Phase 0.5)

From Phase 0.5 onward, the `noble` implementation for every curve SHALL come from a vendor-fork of `@noble/curves` stored inside this package, not from the `@noble/curves` npm package.

#### Scenario: No external runtime dependency on @noble/curves (post-0.5)

- **WHEN** `packages/universal/crypto-curve/package.json` is inspected after Phase 0.5 completes
- **THEN** `@noble/curves` does not appear in `dependencies` or `peerDependencies`
- **AND** `src/vendored/` contains the forked source with its original LICENSE preserved
- **AND** `NOBLE_UPSTREAM.md` records the pinned upstream commit SHA and sync date

### Requirement: Dangerous-tier CI gate

Every primitive in this package belongs to the **dangerous tier**. A curve's default SHALL NOT be changed from `'noble'` to `'native'` in `crypto.config.ts` unless the flip PR demonstrates all gates required by `crypto-hash`, **plus** a third-party cryptographic audit sign-off covering the specific native implementation being flipped.

#### Scenario: Audit required to flip

- **WHEN** a PR modifies `crypto.config.ts` to change a curve entry from `'noble'` to `'native'`
- **THEN** the flip PR template requires an audit report (PDF + auditor signature) attached to the PR
- **AND** the audit report references the exact commit SHA of the native impl
- **AND** the merge is blocked without a valid audit attachment

### Requirement: Constant-time curve math

Native curve implementations SHALL NOT contain data-dependent branches on private-key material, scalar values, or intermediate field elements derived from secrets. Array indexing on secret values is prohibited.

#### Scenario: Constant-time lint enforces this

- **WHEN** any `impl/*.native.ts` in this package is modified
- **THEN** `scripts/ct-lint.ts` scans for the prohibited patterns
- **AND** any match fails CI with a line-level diagnostic