feat(abstract-utxo): update backup key recovery to use standard address generation

Remove deprecated createMultiSigAddress function and update the backup
key recovery flow to use the standard address generation functions.
This ensures consistency with the rest of the codebase and improves
maintainability.

Issue: BG-62668

Co-authored-by: llm-git <llm-git@ttll.de>

Author: OttoAllmendinger

modules/abstract-utxo/src/abstractUtxoCoin.ts

@@ -814,27 +814,6 @@ export abstract class AbstractUtxoCoin extends BaseCoin {
     return explainTx(this.decodeTransactionFromPrebuild(params), params, this.network);
   }
 
-  /**
-   * Create a multisig address of a given type from a list of keychains and a signing threshold
-   * @param addressType
-   * @param signatureThreshold
-   * @param keys
-   */
-  createMultiSigAddress(addressType: ScriptType2Of3, signatureThreshold: number, keys: Buffer[]): MultiSigAddress {
-    const {
-      scriptPubKey: outputScript,
-      redeemScript,
-      witnessScript,
-    } = utxolib.bitgo.outputScripts.createOutputScript2of3(keys, addressType);
-
-    return {
-      outputScript,
-      redeemScript,
-      witnessScript,
-      address: utxolib.address.fromOutputScript(outputScript, this.network),
-    };
-  }
-
   /**
    * @deprecated - use {@see backupKeyRecovery}
    * Builds a funds recovery transaction without BitGo

modules/abstract-utxo/src/recovery/backupKeyRecovery.ts

@@ -15,8 +15,9 @@ import {
 } from '@bitgo/sdk-core';
 import { getMainnet, networks } from '@bitgo/utxo-lib';
 
-import { AbstractUtxoCoin, MultiSigAddress } from '../abstractUtxoCoin';
+import { AbstractUtxoCoin } from '../abstractUtxoCoin';
 import { signAndVerifyPsbt } from '../sign';
+import { generateAddressWithChainAndIndex } from '../address';
 
 import { forCoin, RecoveryProvider } from './RecoveryProvider';
 import { MempoolApi } from './mempoolApi';
@@ -125,14 +126,6 @@ export interface RecoverParams {
   feeRate?: number;
 }
 
-function getFormattedAddress(coin: AbstractUtxoCoin, address: MultiSigAddress) {
-  // Blockchair uses cashaddr format when querying the API for address information. Convert legacy addresses to cashaddr
-  // before querying the API.
-  return coin.getChain() === 'bch' || coin.getChain() === 'bcha'
-    ? coin.canonicalAddress(address.address, 'cashaddr').split(':')[1]
-    : address.address;
-}
-
 async function queryBlockchainUnspentsPath(
   coin: AbstractUtxoCoin,
   params: RecoverParams,
@@ -157,10 +150,12 @@ async function queryBlockchainUnspentsPath(
   }
 
   async function gatherUnspents(addrIndex: number) {
-    const walletKeysForUnspent = walletKeys.deriveForChainAndIndex(chain, addrIndex);
-    const address = coin.createMultiSigAddress(scriptType, 2, walletKeysForUnspent.publicKeys);
+    const keychains = walletKeys.triple.map((k) => ({ pub: k.neutered().toBase58() }));
+    const format = coin.getChain() === 'bch' || coin.getChain() === 'bcha' ? 'cashaddr' : undefined;
+    const address = generateAddressWithChainAndIndex(coin.network, keychains, chain, addrIndex, format);
 
-    const formattedAddress = getFormattedAddress(coin, address);
+    // Blockchair uses cashaddr format when querying the API for address information. Strip the prefix for BCH/BCHA.
+    const formattedAddress = format === 'cashaddr' ? address.split(':')[1] : address;
     const addrInfo = await recoveryProvider.getAddressInfo(formattedAddress);
     // we use txCount here because it implies usage - having tx'es means the addr was generated and used
     if (addrInfo.txCount === 0) {
@@ -169,7 +164,7 @@ async function queryBlockchainUnspentsPath(
       numSequentialAddressesWithoutTxs = 0;
 
       if (addrInfo.balance > 0) {
-        console.log(`Found an address with balance: ${address.address} with balance ${addrInfo.balance}`);
+        console.log(`Found an address with balance: ${address} with balance ${addrInfo.balance}`);
         const addressUnspents = await recoveryProvider.getUnspentsForAddresses([formattedAddress]);
         const processedUnspents = await Promise.all(
           addressUnspents.map(async (u): Promise<WalletUnspent<bigint>> => {
@@ -375,9 +370,9 @@ export async function backupKeyRecovery(
   const recoveryAmount = totalInputAmount - approximateFee - krsFee;
 
   if (recoveryAmount < BigInt(0)) {
-    throw new Error(`this wallet\'s balance is too low to pay the fees specified by the KRS provider. 
+    throw new Error(`this wallet\'s balance is too low to pay the fees specified by the KRS provider.
           Existing balance on wallet: ${totalInputAmount.toString()}. Estimated network fee for the recovery transaction
-          : ${approximateFee.toString()}, KRS fee to pay: ${krsFee.toString()}. After deducting fees, your total 
+          : ${approximateFee.toString()}, KRS fee to pay: ${krsFee.toString()}. After deducting fees, your total
           recoverable balance is ${recoveryAmount.toString()}`);
   }