How can I sign and execute transactions using custom origin(20 bytes address) in PolkadotJS

Question

I have a pallet which ensures a particular custom origin of H160(20 bytes). Actually, this pallet is to ensure that the Origin is that of an ethereum address(20 bytes).

I am therefore writing Integration tests using PolkadotJS, how can i send and sign a transaction by using a 20 bytes address origin?

Answer 1

Looks like Ethereum is supported in @polkadot/keyring:

const PairFromSeed = {
  ecdsa: (seed: Uint8Array): Keypair => secp256k1FromSeed(seed),
  ed25519: (seed: Uint8Array): Keypair => ed25519FromSeed(seed),
  ethereum: (seed: Uint8Array): Keypair => secp256k1FromSeed(seed),
  sr25519: (seed: Uint8Array): Keypair => sr25519FromSeed(seed)
};

• https://github.com/polkadot-js/common/blob/dcf214f250d6effcb99629968e5a3de1468b31af/packages/keyring/src/keyring.ts#LL14C1-L19C3

So you could do something like this:

// Import the keyring as required
import Keyring from '@polkadot/keyring';

// Create a keyring instance
const keyring = new Keyring({ type: 'ethereum' });

Moonbeam has excellent docs on this. As well as an example script:

import { ApiPromise, WsProvider } from '@polkadot/api';
import { Keyring } from '@polkadot/api';

const wsProvider = new WsProvider('WSS-API-ENDPOINT-HERE');
const api = await ApiPromise.create({ provider: wsProvider });

const keyring = new Keyring({ type: 'ethereum' });

const alice = keyring.addFromUri('ALICE-ACCOUNT-PRIVATE-KEY-HERE');
const bob = 'BOB-ACCOUNT-PUBLIC-KEY-HERE';

const tx = await api.tx.balances
  .transfer(bob, 12345n)

const encodedCallData = tx.method.toHex()
console.log(encodedCallData)

const txHash = await tx
  .signAndSend(alice);

console.log(`Submitted with hash ${txHash}`);

// Disconnect the API
api.disconnect();

• https://docs.moonbeam.network/builders/build/substrate-api/polkadot-js-api/#transactions