feat: support for schnorr signatures

features/keychain/module/__tests__/schnorr.test.js

@@ -0,0 +1,58 @@
+import { utils } from '@noble/secp256k1'
+import ecc from '@exodus/bitcoinerlab-secp256k1'
+
+import { create } from '../crypto/secp256k1'
+
+const fixtures = [
+  {
+    // fixtures created by logging inside toAsyncSigner: https://github.com/ExodusMovement/assets/blob/5f93b19e7537f92519ec9bb7fe2514db9b4507e0/bitcoin/bitcoin-api/src/tx-sign/taproot.js#L48
+    priv: '90de83eea26049afc40ba7d13fd8d4537331cd226f17051c97ca56c696af66b5',
+    pub: '0273ae16fb2721654c8735487c024f9a137511eb2d4f2c39e3084bd87cf044ac91',
+    tweak: '316fb252f50a55c468b86b951093b5a56d8cac0a178d066899b9520c694ce8c6',
+    priv2: 'c24e3641976a9f742cc41366506c89f8e0be792c86a40b853183a8d2fffc4f7b',
+    pub2: '02c24e41b8ec4d091f9bfbb481fde7ce0808ed820db8e93409cc404da8b9de7e92',
+    buffer: '52be7b43a029336afb5bca87f33b5cbe1a84d70e321db62dc12c14eac3c8b3a3',
+    entropy: '1230000000000000000000000000000000000000000000000000000000000000',
+    sig: 'c2259b1fc27b846b7204b571a43e4951ef53e40b7486732673ac8d9187eb95d230ccdc5ab20e4e1e975fb211d13531de77f3ea70397fcca8d74629d20ffb4a3f',
+  },
+  {
+    priv: 'fc7458de3d5616e7803fdc81d688b9642641be32fee74c4558ce680cac3d4111',
+    pub: '03d734e09fc6ed105225ff316c6fa74f89096f90a437b1c7001af6d0b244d6f151',
+    priv2: '8c28b8720947067702dc9e0b81c2c89d6f97e14cc65db22a1849d9ce685202e9',
+    pub2: '0351adaba657ce3a0758dc1a3e37be9d86048288f26674f503d2d2366010680f17',
+    buffer: '7cb987eb16b030b09f34e3ae52e8fb3a9b6e0caaea3021e0ab4dc15ccd0188bb',
+    entropy: '0000000000000000000000000000000000000000000000000000000000000000',
+    sig: 'e397d713d4832069e7a6794f62d23e7f7f8d8670aa1ebb72872ad8cb908a2575b2c71746f795bbfdba3e433e80b08ce1b5454cb2a349b25111c269b9f625cf8d',
+  },
+]
+
+const tapTweakHash = (publicKey, h) => {
+  const xOnlyPoint = ecc.xOnlyPointFromPoint(publicKey)
+  const hash = utils.taggedHashSync('TapTweak', Buffer.concat(h ? [xOnlyPoint, h] : [xOnlyPoint]))
+  return Buffer.from(hash)
+}
+
+describe('Schnorr signer', () => {
+  test.each(fixtures)('signSchnorr should sign buffer with tweaked key', async (fixture) => {
+    const getPrivateHDKey = () => ({
+      privateKey: Buffer.from(fixture.priv, 'hex'),
+      publicKey: Buffer.from(fixture.pub, 'hex'),
+    })
+    const secp256k1Signer = create({ getPrivateHDKey })
+
+    let tweak
+    if (fixture.tweak) {
+      const publicKey = getPrivateHDKey().publicKey
+      tweak = tapTweakHash(publicKey)
+      expect(tweak.toString('hex')).toBe(fixture.tweak)
+    }
+
+    const result = await secp256k1Signer.signSchnorr({
+      data: Buffer.from(fixture.buffer, 'hex'),
+      tweak,
+      extraEntropy: Buffer.from(fixture.entropy, 'hex'),
+    })
+
+    expect(Buffer.from(result).toString('hex')).toBe(fixture.sig)
+  })
+})

features/keychain/module/crypto/secp256k1.js

@@ -1,8 +1,11 @@
 import assert from 'minimalistic-assert'
 import elliptic from '@exodus/elliptic'
 import { mapValues, pick } from '@exodus/basic-utils'
+import ecc from '@exodus/bitcoinerlab-secp256k1'
 
-const validEcOptions = (ecOptions) =>
+import { tweakPrivateKey } from './tweak'
+
+const isValidEcOptions = (ecOptions) =>
   !ecOptions || Object.keys(ecOptions).every((key) => ['canonical'].includes(key))
 
 export const create = ({ getPrivateHDKey }) => {
@@ -12,11 +15,16 @@ export const create = ({ getPrivateHDKey }) => {
   const createInstance = () => ({
     signBuffer: async ({ seedId, keyId, data, ecOptions, enc = 'der' }) => {
       assert(['der', 'raw'].includes(enc), 'signBuffer: invalid enc')
-      assert(validEcOptions(ecOptions), 'signBuffer: invalid EC option')
+      assert(isValidEcOptions(ecOptions), 'signBuffer: invalid EC option')
       const { privateKey } = getPrivateHDKey({ seedId, keyId })
       const signature = curve.sign(data, privateKey, pick(ecOptions, ['canonical']))
       return enc === 'der' ? Buffer.from(signature.toDER()) : { ...signature }
     },
+    signSchnorr: async ({ seedId, keyId, data, tweak, extraEntropy }) => {
+      const hdkey = getPrivateHDKey({ seedId, keyId })
+      const privateKey = tweak ? tweakPrivateKey({ hdkey, tweak }) : hdkey.privateKey
+      return ecc.signSchnorr(data, privateKey, extraEntropy)
+    },
   })
 
   // For backwards compatibility

features/keychain/module/crypto/tweak.js

@@ -0,0 +1,13 @@
+import assert from 'minimalistic-assert'
+import ecc from '@exodus/bitcoinerlab-secp256k1'
+
+export const tweakPrivateKey = ({ hdkey, tweak }) => {
+  const { privateKey, publicKey } = hdkey
+  assert(ecc.isPrivate(privateKey), 'tweakPrivateKey: expected valid private key')
+  assert(ecc.isPointCompressed(publicKey), 'tweakPrivateKey: expected compressed public key')
+
+  let tweakedPrivateKey = publicKey[0] === 3 ? ecc.privateNegate(privateKey) : privateKey
+  tweakedPrivateKey = ecc.privateAdd(tweakedPrivateKey, tweak)
+
+  return Buffer.from(tweakedPrivateKey)
+}

features/keychain/package.json

@@ -31,6 +31,7 @@
   "dependencies": {
     "@exodus/basic-utils": "^2.0.0",
     "@exodus/bip32": "^2.1.0",
+    "@exodus/bitcoinerlab-secp256k1": "^1.0.5-exodus.1",
     "@exodus/elliptic": "^6.5.4-precomputed",
     "@exodus/key-identifier": "^1.0.1",
     "@exodus/key-utils": "^3.0.0",
@@ -44,6 +45,7 @@
   },
   "devDependencies": {
     "@exodus/key-ids": "^1.0.0",
+    "@noble/secp256k1": "^1.7.1",
     "bip39": "2.6.0",
     "bn.js": "^5.2.1",
     "eslint": "^8.44.0",

yarn.lock

@@ -1834,6 +1834,16 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@exodus/bitcoinerlab-secp256k1@npm:^1.0.5-exodus.1":
+  version: 1.0.5-exodus.1
+  resolution: "@exodus/bitcoinerlab-secp256k1@npm:1.0.5-exodus.1"
+  dependencies:
+    "@noble/hashes": ^1.1.5
+    "@noble/secp256k1": ^1.7.1
+  checksum: b9ba53bdf8eee1af328633fe772f592d0dbbd2a6bc8a7c5518028133d7a26a2f377daa8551ddc27dd1932c808ecac6baff153aec655fc98f0153b4aa707f02e3
+  languageName: node
+  linkType: hard
+
 "@exodus/elliptic@npm:6.5.4-precomputed, @exodus/elliptic@npm:^6.5.4-precomputed":
   version: 6.5.4-precomputed
   resolution: "@exodus/elliptic@npm:6.5.4-precomputed"
@@ -2027,12 +2037,14 @@ __metadata:
   dependencies:
     "@exodus/basic-utils": ^2.0.0
     "@exodus/bip32": ^2.1.0
+    "@exodus/bitcoinerlab-secp256k1": ^1.0.5-exodus.1
     "@exodus/elliptic": ^6.5.4-precomputed
     "@exodus/key-identifier": ^1.0.1
     "@exodus/key-ids": ^1.0.0
     "@exodus/key-utils": ^3.0.0
     "@exodus/slip10": ^1.0.0
     "@exodus/sodium-crypto": ^3.1.0
+    "@noble/secp256k1": ^1.7.1
     bip39: 2.6.0
     bn.js: ^5.2.1
     buffer-json: ^2.0.0
@@ -2614,6 +2626,20 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@noble/hashes@npm:^1.1.5":
+  version: 1.4.0
+  resolution: "@noble/hashes@npm:1.4.0"
+  checksum: 8ba816ae26c90764b8c42493eea383716396096c5f7ba6bea559993194f49d80a73c081f315f4c367e51bd2d5891700bcdfa816b421d24ab45b41cb03e4f3342
+  languageName: node
+  linkType: hard
+
+"@noble/secp256k1@npm:^1.7.1":
+  version: 1.7.1
+  resolution: "@noble/secp256k1@npm:1.7.1"
+  checksum: d2301f1f7690368d8409a3152450458f27e54df47e3f917292de3de82c298770890c2de7c967d237eff9c95b70af485389a9695f73eb05a43e2bd562d18b18cb
+  languageName: node
+  linkType: hard
+
 "@nodelib/fs.scandir@npm:2.1.5":
   version: 2.1.5
   resolution: "@nodelib/fs.scandir@npm:2.1.5"