## ADDED Requirements

### Requirement: Universal AEAD primitive surface

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

#### Scenario: AEAD primitives available

- **WHEN** a consumer imports from `@suaveplan/crypto-cipher`
- **THEN** `aes256gcm`, `chacha20poly1305`, `xchacha20poly1305` are exported
- **AND** each primitive exposes `encrypt(key, nonce, plaintext, aad?)` and `decrypt(key, nonce, ciphertext, aad?)` returning / consuming `Uint8Array`
- **AND** each primitive is also exported from the subpath `@suaveplan/crypto-cipher/<id>` for tree-shaking

### Requirement: Per-primitive replaceability

Every AEAD in `@suaveplan/crypto-cipher` 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 AEAD has both impl files

- **WHEN** the package is inspected
- **THEN** every primitive 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 AEAD SHALL come from a vendor-fork of `@noble/ciphers` stored inside this package, not from the `@noble/ciphers` npm package.

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

- **WHEN** `packages/universal/crypto-cipher/package.json` is inspected after Phase 0.5
- **THEN** `@noble/ciphers` 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**. An AEAD'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 an AEAD 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 being flipped

### Requirement: Constant-time block-cipher and MAC implementation

Native AES implementations SHALL be bitsliced or use hardware intrinsics — table-lookup AES is prohibited. Native Poly1305 and GHASH implementations SHALL NOT contain data-dependent branches.

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

- **WHEN** any `impl/*.native.ts` in this package is modified
- **THEN** `scripts/ct-lint.ts` scans for prohibited patterns (secret-indexed array access, data-dependent branches, early returns on tag comparison)
- **AND** any match fails CI with a line-level diagnostic

### Requirement: Nonce handling is the caller's responsibility

Primitives in this package SHALL NOT generate nonces internally. All nonce inputs are supplied by the caller.

#### Scenario: No internal random nonce

- **WHEN** `encrypt(...)` is invoked
- **THEN** no call to a CSPRNG is made inside the primitive
- **AND** the nonce parameter is required and validated for length