Add exportRawSecretKey() and exportRawPublicKey() to key pair API.

CHANGELOG.md

@@ -1,5 +1,10 @@
 # @digitalbazaar/ecdsa-multikey ChangeLog
 
+## 1.4.0 - 2023-11-dd
+
+### Added
+- Add `exportRawSecretKey()` and `exportRawPublicKey()` to key pair interface.
+
 ## 1.3.0 - 2023-10-31
 
 ### Added

lib/index.js

@@ -10,7 +10,9 @@ import {
 import {CryptoKey, webcrypto} from './crypto.js';
 import {createSigner, createVerifier} from './factory.js';
 import {
- exportKeyPair, importKeyPair, toPublicKeyMultibase, toSecretKeyMultibase
+ exportKeyPair, importKeyPair,
+ toPublicKeyBytes, toSecretKeyBytes,
+ toPublicKeyMultibase, toSecretKeyMultibase
 } from './serialize.js';
 import {getSecretKeySize} from './helpers.js';
 import {toMultikey} from './translators.js';
@@ -23,8 +25,7 @@ export async function generate({
  if(!curve) {
  throw new TypeError(
  '"curve" must be one of the following values: ' +
- `${Object.values(ECDSA_CURVE).map(v => `'${v}'`).join(', ')}.`
- );
+ `${Object.values(ECDSA_CURVE).map(v => `'${v}'`).join(', ')}.`);
  }
  const algorithm = keyAgreement ?
  {name: 'ECDH', namedCurve: curve} : {name: ALGORITHM, namedCurve: curve};
@@ -126,6 +127,14 @@ async function _createKeyPairInterface({keyPair, keyAgreement = false}) {
  }
  return _deriveSecret(
  {localKeyPair: this, remoteKeyPair: remotePublicKey});
+ },
+ async exportRawPublicKey() {
+ const jwk = await toJwk({keyPair: this});
+ return toPublicKeyBytes({jwk});
+ },
+ async exportRawSecretKey() {
+ const jwk = await toJwk({keyPair: this, secretKey: true});
+ return toSecretKeyBytes({jwk});
  }
  };
 
@@ -143,8 +152,7 @@ function _assertMultikey(key) {
  if(key['@context'] !== MULTIKEY_CONTEXT_V1_URL) {
  throw new TypeError(
  '"key" must be a Multikey with context ' +
- `"${MULTIKEY_CONTEXT_V1_URL}".`
- );
+ `"${MULTIKEY_CONTEXT_V1_URL}".`);
  }
 }
 

lib/serialize.js

@@ -156,6 +156,26 @@ export async function importKeyPair({
  return keyPair;
 }
 
+export function toPublicKeyBytes({jwk} = {}) {
+ if(jwk?.kty !== 'EC') {
+ throw new TypeError('"jwk.kty" must be "EC".');
+ }
+ const {crv: curve} = jwk;
+ const secretKeySize = getSecretKeySize({curve});
+ // convert `x` coordinate to compressed public key
+ const x = base64url.decode(jwk.x);
+ const y = base64url.decode(jwk.y);
+ // public key size is always secret key size + 1
+ const publicKeySize = secretKeySize + 1;
+ const publicKey = new Uint8Array(publicKeySize);
+ // use even / odd status of `y` coordinate for compressed header
+ const even = y[y.length - 1] % 2 === 0;
+ publicKey[0] = even ? 2 : 3;
+ // write `x` coordinate at end of multikey buffer to zero-fill it
+ publicKey.set(x, publicKey.length - x.length);
+ return publicKey;
+}
+
 export function toPublicKeyMultibase({jwk} = {}) {
  if(jwk?.kty !== 'EC') {
  throw new TypeError('"jwk.kty" must be "EC".');
@@ -179,6 +199,19 @@ export function toPublicKeyMultibase({jwk} = {}) {
  return publicKeyMultibase;
 }
 
+export function toSecretKeyBytes({jwk} = {}) {
+ if(jwk?.kty !== 'EC') {
+ throw new TypeError('"jwk.kty" must be "EC".');
+ }
+ const {crv: curve} = jwk;
+ const secretKeySize = getSecretKeySize({curve});
+ const d = base64url.decode(jwk.d);
+ const secretKey = new Uint8Array(secretKeySize);
+ // write `d` at end of multikey buffer to zero-fill it
+ secretKey.set(d, secretKey.length - d.length);
+ return secretKey;
+}
+
 export function toSecretKeyMultibase({jwk} = {}) {
  if(jwk?.kty !== 'EC') {
  throw new TypeError('"jwk.kty" must be "EC".');

test/EcdsaMultikey.spec.js

@@ -2,10 +2,10 @@
  * Copyright (c) 2023 Digital Bazaar, Inc. All rights reserved.
  */
 import * as base58 from 'base58-universal';
+import * as EcdsaMultikey from '../lib/index.js';
 import chai from 'chai';
 import {CryptoKey, webcrypto} from '../lib/crypto.js';
 import {getNamedCurveFromPublicMultikey} from '../lib/helpers.js';
-import * as EcdsaMultikey from '../lib/index.js';
 import {exportKeyPair} from '../lib/serialize.js';
 import {
  mockKey,
@@ -134,8 +134,7 @@ describe('EcdsaMultikey', () => {
  it('should only export secret key if available', async () => {
  const algorithm = {name: 'ECDSA', namedCurve: 'P-256'};
  const keyPair = await webcrypto.subtle.generateKey(
- algorithm, true, ['sign', 'verify']
- );
+ algorithm, true, ['sign', 'verify']);
  delete keyPair.privateKey;
 
  const keyPairExported = await exportKeyPair({
@@ -147,6 +146,22 @@ describe('EcdsaMultikey', () => {
 
  expect(keyPairExported).not.to.have.property('secretKeyMultibase');
  });
+
+ it('should export raw public key', async () => {
+ const keyPair = await EcdsaMultikey.generate({curve: 'P-256'});
+ const expectedPublicKey = base58.decode(
+ keyPair.publicKeyMultibase.slice(1)).slice(2);
+ const publicKey = await keyPair.exportRawPublicKey();
+ expect(expectedPublicKey).to.deep.equal(publicKey);
+ });
+
+ it('should export raw secret key', async () => {
+ const keyPair = await EcdsaMultikey.generate({curve: 'P-256'});
+ const expectedSecretKey = base58.decode(
+ keyPair.secretKeyMultibase.slice(1)).slice(2);
+ const secretKey = await keyPair.exportRawSecretKey();
+ expect(expectedSecretKey).to.deep.equal(secretKey);
+ });
  });
 
  describe('from', () => {