# crypto-curve ## Purpose Elliptic-curve primitives for the Suaveplan monorepo: secp256k1 (Bitcoin / Ethereum) including ECDSA recovery, ed25519 signing, x25519 key agreement, and the NIST curves p256, p384, p521. Per-primitive selector layout enables flipping the default backend from noble to a native engine without changing any caller imports. ## 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`, `p384`, `p521` 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/` 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//impl/.noble.ts` and `src/primitives//impl/.native.ts` - **AND** the `native.ts` file is either a working implementation or a stub that throws `PrimitiveNotImplemented('')` ### 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 ### Requirement: secp256k1 ECDSA signing with recovery byte The `secp256k1` primitive SHALL expose `signWithRecovery(digest, privateKey)` returning a 65-byte signature (64-byte compact signature followed by a single recovery byte). The recovery byte SHALL be the byte returned by `secp256k1.sign(digest, privateKey).recovery` from the `@noble/curves` library; valid values are `0` or `1`. #### Scenario: produces 65-byte signature - **WHEN** `signWithRecovery(digest, privateKey)` is called for a valid digest and private key - **THEN** the result is a `Uint8Array` of length 65 AND `result[64]` is `0` or `1` #### Scenario: signWithRecovery output verifies via standard verify - **WHEN** the first 64 bytes of `signWithRecovery(digest, privateKey)` are passed to the existing `verify(digest, sig64, publicKey)` - **THEN** the signature verifies successfully **Verified by:** `packages/crypto/crypto-curve/src/primitives/secp256k1/secp256k1.test.ts::"signWithRecovery returns 65-byte signature with recovery byte 0 or 1"` AND `packages/crypto/crypto-curve/src/primitives/secp256k1/secp256k1.test.ts::"signWithRecovery output verifies via standard verify on first 64 bytes"` --- ### Requirement: secp256k1 public-key recovery The `secp256k1` primitive SHALL expose `recoverPublicKey(signatureWithRecovery, digest)` returning the 33-byte compressed public key recovered from a 65-byte signature-with-recovery and the original digest. Inputs may be supplied as `Uint8Array` or hex strings. #### Scenario: recovers the signing public key - **WHEN** `signWithRecovery(digest, privateKey)` produces `sig` and `recoverPublicKey(sig, digest)` is called - **THEN** the recovered public key equals `getPublicKey(privateKey)` byte-for-byte #### Scenario: missing recovery byte rejected - **WHEN** a 64-byte signature (without recovery byte) is passed to `recoverPublicKey` - **THEN** it throws `SuaveplanError` with code `CRYPTO_CURVE.RECOVERY_BYTE_MISSING` and `context.signatureLength === 64` #### Scenario: invalid recovery byte rejected - **WHEN** a 65-byte signature is passed but `signatureWithRecovery[64]` is `2`, `3`, or any value > 3 - **THEN** it throws `SuaveplanError` with code `CRYPTO_CURVE.RECOVERY_BYTE_INVALID` and `context.recoveryByte` reflects the offending value **Verified by:** `packages/crypto/crypto-curve/src/primitives/secp256k1/secp256k1.test.ts::"recoverPublicKey returns the same key as getPublicKey for the signer"` AND `packages/crypto/crypto-curve/src/primitives/secp256k1/secp256k1.spec-conformance.test.ts::"throws RECOVERY_BYTE_MISSING for 64-byte signature"` AND `packages/crypto/crypto-curve/src/primitives/secp256k1/secp256k1.spec-conformance.test.ts::"throws RECOVERY_BYTE_INVALID when recovery byte is out of range"` --- ### Requirement: secp256k1 verify-with-recovery The `secp256k1` primitive SHALL expose `verifyWithRecovery(signatureWithRecovery, digest, expectedPublicKey)` returning `true` only when the public key recovered from the signature equals `expectedPublicKey` (compared in constant time on the byte buffer). When the recovered key differs, the function SHALL return `false` (it does NOT throw on mismatch — mismatch is a routine path). #### Scenario: returns true on matching key - **WHEN** `verifyWithRecovery(sig, digest, expectedPublicKey)` is called with the public key that produced `sig` - **THEN** the result is `true` #### Scenario: returns false on non-matching key - **WHEN** `verifyWithRecovery(sig, digest, otherPublicKey)` is called with a public key that did not produce `sig` - **THEN** the result is `false` (no exception is thrown) #### Scenario: comparison is constant-time - **WHEN** the recovered public key and `expectedPublicKey` differ in their first byte vs differ only in their last byte - **THEN** the timing distribution observed across many invocations does not reveal the position of the difference (verified via a statistical timing test) **Verified by:** `packages/crypto/crypto-curve/src/primitives/secp256k1/secp256k1.test.ts::"verifyWithRecovery returns true on matching public key"` AND `packages/crypto/crypto-curve/src/primitives/secp256k1/secp256k1.test.ts::"verifyWithRecovery returns false on non-matching public key"` AND `packages/crypto/crypto-curve/src/primitives/secp256k1/secp256k1.spec-conformance.test.ts::"verifyWithRecovery comparison is constant-time"` --- ### Requirement: NIST P-384 (secp384r1) ECDSA primitive The package SHALL export a `p384` namespace from the root barrel and a matching `./p384` subpath export, providing `getPublicKey`, `sign`, `verify`, and `randomPrivateKey`. Private keys SHALL be 48 bytes, compressed public keys SHALL be 49 bytes, and compact ECDSA signatures SHALL be 96 bytes. Callers SHALL pre-hash messages; the module operates on digests. The selector SHALL forward to the noble-backed implementation by default; the native implementation SHALL throw `PrimitiveNotImplemented("p384")` until a WebCrypto bridge lands. #### Scenario: P-384 sign + verify round-trip - **GIVEN** a freshly-generated P-384 private key and 48-byte digest - **WHEN** `verify(sign(digest, sk), digest, getPublicKey(sk))` is computed - **THEN** the result is `true` AND the signature length is 96 bytes #### Scenario: P-384 verify rejects tampered signature - **WHEN** a single byte of a valid P-384 signature is XORed with `0xff` - **THEN** `verify` returns `false` #### Scenario: P-384 verify returns false on malformed inputs - **WHEN** `verify` is invoked with non-`Uint8Array` inputs or empty buffers - **THEN** the call returns `false` (does not throw) **Verified by:** `packages/crypto/crypto-curve/src/primitives/p384/p384.test.ts::"sign + verify round-trips"` AND `…::"verify returns false for tampered signature (no throw)"` AND `…::"verify returns false for bogus input (caught)"` --- ### Requirement: NIST P-521 (secp521r1) ECDSA primitive The package SHALL export a `p521` namespace from the root barrel and a matching `./p521` subpath export, providing `getPublicKey`, `sign`, `verify`, and `randomPrivateKey`. Private keys SHALL be 66 bytes (521-bit scalar left-padded to a byte boundary), compressed public keys SHALL be 67 bytes, and compact ECDSA signatures SHALL be 132 bytes. Callers SHALL pre-hash messages; the module operates on digests. The selector SHALL forward to the noble-backed implementation by default; the native implementation SHALL throw `PrimitiveNotImplemented("p521")`. #### Scenario: P-521 sign + verify round-trip - **GIVEN** a freshly-generated P-521 private key and 64-byte digest - **WHEN** `verify(sign(digest, sk), digest, getPublicKey(sk))` is computed - **THEN** the result is `true` AND the signature length is 132 bytes #### Scenario: P-521 verify rejects tampered signature - **WHEN** a single byte of a valid P-521 signature is XORed with `0xff` - **THEN** `verify` returns `false` #### Scenario: P-521 verify returns false on malformed inputs - **WHEN** `verify` is invoked with non-`Uint8Array` inputs or empty buffers - **THEN** the call returns `false` (does not throw) **Verified by:** `packages/crypto/crypto-curve/src/primitives/p521/p521.test.ts::"sign + verify round-trips"` AND `…::"verify returns false for tampered signature (no throw)"` AND `…::"verify returns false for bogus input (caught)"`