feat: Taproot swaps (#611)

package.json

@@ -49,6 +49,7 @@
     "@nestjs/throttler": "^5.0.1",
     "@nestjs/websockets": "^10.2.10",
     "@tanstack/react-table": "^8.10.7",
+    "@vulpemventures/secp256k1-zkp": "^3.2.1",
     "apollo-server-express": "^3.13.0",
     "balanceofsatoshis": "^17.5.2",
     "bcryptjs": "^2.4.3",
@@ -57,7 +58,7 @@
     "bip32": "^4.0.0",
     "bip39": "^3.1.0",
     "bitcoinjs-lib": "^6.1.5",
-    "boltz-core": "^1.0.4",
+    "boltz-core": "^2.1.1",
     "cookie": "^0.6.0",
     "cross-env": "^7.0.3",
     "crypto-js": "^4.1.1",

schema.gql

@@ -489,7 +489,7 @@ type MessageType {
 type Mutation {
   addPeer(isTemporary: Boolean, publicKey: String, socket: String, url: String): Boolean!
   bosRebalance(avoid: [String!], in_through: String, max_fee: Float, max_fee_rate: Float, max_rebalance: Float, node: String, out_inbound: Float, out_through: String, timeout_minutes: Float): BosRebalanceResult!
-  claimBoltzTransaction(destination: String!, fee: Float!, preimage: String!, privateKey: String!, redeem: String!, transaction: String!): String!
+  claimBoltzTransaction(destination: String!, fee: Float!, id: String!, preimage: String!, privateKey: String!, redeem: String!, transaction: String!): String!
   claimGhostAddress(address: String): ClaimGhostAddress!
   closeChannel(forceClose: Boolean, id: String!, targetConfirmations: Float, tokensPerVByte: Float): OpenOrCloseChannel!
   createAddress(type: String! = "p2tr"): String!

src/client/src/graphql/mutations/claimBoltzTransaction.ts

@@ -2,6 +2,7 @@ import { gql } from '@apollo/client';
 
 export const CLAIM_BOLTZ_TRANSACTION = gql`
   mutation ClaimBoltzTransaction(
+    $id: String!
     $redeem: String!
     $transaction: String!
     $preimage: String!
@@ -10,6 +11,7 @@ export const CLAIM_BOLTZ_TRANSACTION = gql`
     $fee: Float!
   ) {
     claimBoltzTransaction(
+      id: $id
       redeem: $redeem
       transaction: $transaction
       preimage: $preimage

src/client/src/graphql/types.ts

@@ -628,6 +628,7 @@ export type MutationBosRebalanceArgs = {
 export type MutationClaimBoltzTransactionArgs = {
   destination: Scalars['String']['input'];
   fee: Scalars['Float']['input'];
+  id: Scalars['String']['input'];
   preimage: Scalars['String']['input'];
   privateKey: Scalars['String']['input'];
   redeem: Scalars['String']['input'];

src/client/src/views/swap/SwapClaim.tsx

@@ -77,7 +77,8 @@ export const SwapClaim = () => {
   }
 
   const claimingSwap = swaps[claim];
-  const { redeemScript, preimage, receivingAddress, privateKey } = claimingSwap;
+  const { redeemScript, preimage, receivingAddress, privateKey, id } =
+    claimingSwap;
 
   if (!preimage || !transactionHex || !privateKey) {
     return <Missing />;
@@ -129,7 +130,7 @@ export const SwapClaim = () => {
           </MultiButton>
         </InputWithDeco>
       )}
-      <InputWithDeco title={'Fee Amount'} amount={fee * 223} noInput={true}>
+      <InputWithDeco title={'Fee Amount'} amount={fee * 111} noInput={true}>
         {type !== 'none' && (
           <Input
             maxWidth={'240px'}
@@ -176,6 +177,7 @@ export const SwapClaim = () => {
         onClick={() =>
           claimTransaction({
             variables: {
+              id,
               redeem: redeemScript,
               transaction: transactionHex,
               preimage,

src/server/modules/api/boltz/boltz.helpers.ts

@@ -1,5 +1,14 @@
-import { address, Network, networks } from 'bitcoinjs-lib';
-import { ECPairFactory, ECPairAPI } from 'ecpair';
+import { Secp256k1ZKP } from '@vulpemventures/secp256k1-zkp';
+import { address, Network, networks, Transaction } from 'bitcoinjs-lib';
+import {
+  detectSwap,
+  extractRefundPublicKeyFromReverseSwapTree,
+  Musig,
+  TaprootUtils,
+} from 'boltz-core';
+import { SwapTree } from 'boltz-core/dist/lib/consts/Types';
+import { randomBytes } from 'crypto';
+import { ECPairFactory, ECPairAPI, ECPairInterface } from 'ecpair';
 import * as ecc from 'tiny-secp256k1';
 
 const ECPair: ECPairAPI = ECPairFactory(ecc);
@@ -33,3 +42,39 @@ export const generateKeys = (network: Network = networks.bitcoin) => {
     privateKey: getHexString(keys.privateKey),
   };
 };
+
+export const findTaprootOutput = (
+  zkp: Secp256k1ZKP,
+  transaction: Transaction,
+  tree: SwapTree,
+  keys: ECPairInterface
+) => {
+  const theirPublicKey = extractRefundPublicKeyFromReverseSwapTree(tree);
+
+  // "brute force" the tie breaker because it is not in the onchain script
+  // https://medium.com/blockstream/reducing-bitcoin-transaction-sizes-with-x-only-pubkeys-f86476af05d7
+  for (const tieBreaker of ['02', '03']) {
+    const compressedKey = Buffer.concat([
+      getHexBuffer(tieBreaker),
+      theirPublicKey,
+    ]);
+
+    const musig = new Musig(zkp, keys, randomBytes(32), [
+      compressedKey,
+      keys.publicKey,
+    ]);
+    const tweakedKey = TaprootUtils.tweakMusig(musig, tree.tree);
+
+    const swapOutput = detectSwap(tweakedKey, transaction);
+    if (swapOutput !== undefined) {
+      return {
+        musig,
+        tweakedKey,
+        swapOutput,
+        theirPublicKey: compressedKey,
+      };
+    }
+  }
+
+  return undefined;
+};