getAddressFromMnemonic.ts

// Import Ethereum Account from Private Key
import Keyring from '@polkadot/keyring';
import { u8aToHex } from '@polkadot/util';
import { mnemonicToLegacySeed, hdEthereum, cryptoWaitReady } from '@polkadot/util-crypto';
import yargs from 'yargs';

const args = yargs.options({
  mnemonic: { type: 'string', demandOption: true, alias: 'm' },
  index: { type: 'string', demandOption: true, alias: 'i' },
}).argv;

const keyringSR25519 = new Keyring({ type: 'sr25519' });
const keyringECDSA = new Keyring({ type: 'ethereum' });

// Import from Mnemonic
// Define the derivation path
const ethDerPath = "m/44'/60'/0'/0/" + args['index'];
const subsDerPath = '//hard/soft';
console.log(`Mnemonic: ${args['mnemonic']}`);
console.log(`--------------------------\n`);

const main = async () => {
  await cryptoWaitReady();

  // Extract Eth address from mnemonic
  const newPairEth = keyringECDSA.addFromUri(`${args['mnemonic']}/${ethDerPath}`);
  console.log(`Ethereum Derivation Path: ${ethDerPath}`);
  console.log(`Derived Ethereum Address from Mnemonic: ${newPairEth.address}`);

  // Extract private key from mnemonic
  const privateKey = u8aToHex(
    hdEthereum(mnemonicToLegacySeed(args['mnemonic'], '', false, 64), ethDerPath).secretKey
  );
  console.log(`Derived Private Key from Mnemonic: ${privateKey}`);
  console.log(`--------------------------\n`);

  // Extract Substrate address from mnemonic
  const newPairSubstrate = keyringSR25519.addFromUri(`${args['mnemonic']}${subsDerPath}`);
  console.log(`Substrate Derivation Path: ${subsDerPath}`);
  console.log(`Derived Generic Substrate Address from Mnemonic: ${newPairSubstrate.address}`);
};

main();