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Version: v3.x.x

Alchemy Account Kit

Learn how Lit Programmable Key Pairs can be a signer for Alchemy's Account Kit!

Objectives​

At completion of this reading you should be able to:

  • Describe use cases for Account Kit.
  • Understand how to set Lit as a signer to an Account Kit.

What is Account Kit?​

Alchemy's Account Kit is a complete toolkit to embed smart accounts in your app with social login, gas abstraction, batch transactions, and more.

Powered by account abstraction (ERC-4337), Account Kit provides all the tools you need to onboard users with zero friction:

-aa-sdk: a flexible library to integrate, deploy, and use smart accounts -Light Account: a gas-optimized ERC-4337 smart contract account -Signers: integrations with your favorite social login and passkey providers -Gas Manager APIs: a programmable API to sponsor gas fees in your app‍ -Bundler APIs: the most reliable Bundler to submit UserOps onchain at scale

With Account Kit, you can create a smart account for every user. Smart accounts are smart contract wallets that leverage account abstraction to radically simplify every step of the onboarding experience. Now, a new user can:

  • Create a smart account directly in an Account Kit powered app without third-party - downloads
  • Sign up with an email, social login, passkey, or self-custodial wallet
  • Submit transactions without needing ETH in their account for gas
  • Submit transactions in the background without leaving your app

Guide​

Combining Lit PKP wallet with Account Kit allows you to use your Programmable Key Pairs (PKPs) as a smart account for your users.

Pre-requisites​

  • Familiarity with JavaScript and TypeScript.
  • Understand the basics of account abstraction.

1. Setup​

Install the pkp ethers package:

npm i @lit-protocol/pkp-ethers@cayenne

Install the LitNodeClient package`:

npm i @lit-protocol/lit-node-client@cayenne

2. Get A Programmable Key Pair (PKP)​

Get some LIT Testnt tokens from Lit's Chronicle network.

Then mint a PKP through the PKP explorer.

For other ways to obtain a PKP, read more within the Lit docs.

3. Create a SmartAccountSigner​

Next, setup the LitNodeClient and PKPEthersWallet to create a SmartAccountSigner:

import { WalletClientSigner, type SmartAccountSigner } from "@alchemy/aa-core";
import { LitAbility, LitActionResource } from "@lit-protocol/auth-helpers";
import { LitNodeClient } from "@lit-protocol/lit-node-client";
import { PKPEthersWallet } from "@lit-protocol/pkp-ethers";
import { AuthCallbackParams } from "@lit-protocol/types";
import { createWalletClient, custom } from "viem";
import { polygonMumbai } from "viem/chains";

const API_KEY = "<YOUR ALCHEMY API KEY>";
const POLYGON_MUMBAI_RPC_URL = `${polygonMumbai.rpcUrls.alchemy.http[0]}/${API_KEY}`;
const PKP_PUBLIC_KEY = "<YOUR PKP PUBLIC KEY>";

const litNodeClient = new LitNodeClient({
  litNetwork: "cayenne",
  debug: false,
});
await litNodeClient.connect();

const resourceAbilities = [
  {
    resource: new LitActionResource("*"),
    ability: LitAbility.PKPSigning,
  },
];

/**
 * For provisioning keys and setting up authentication methods see documentation below
 * https://developer.litprotocol.com/v2/pkp/minting
 */
const authNeededCallback = async (params: AuthCallbackParams) => {
  const response = await litNodeClient.signSessionKey({
    sessionKey: params.sessionKeyPair,
    statement: params.statement,
    authMethods: [],
    pkpPublicKey: PKP_PUBLIC_KEY,
    expiration: params.expiration,
    resources: params.resources,
    chainId: 1,
  });
  return response.authSig;
};

const sessionSigs = await litNodeClient
  .getSessionSigs({
    chain: "ethereum",
    expiration: new Date(Date.now() + 1000 * 60 * 60 * 24 * 7).toISOString(),
    resourceAbilityRequests: resourceAbilities,
    authNeededCallback,
  })
  .catch((err) => {
    console.log("error while attempting to access session signatures: ", err);
    throw err;
  });

const pkpWallet = new PKPEthersWallet({
  pkpPubKey: PKP_PUBLIC_KEY,
  rpc: POLYGON_MUMBAI_RPC_URL,
  controllerSessionSigs: sessionSigs,
});

// a smart account signer you can use as an owner on ISmartContractAccount
export const litSigner: SmartAccountSigner = new WalletClientSigner(
  createWalletClient({ transport: custom(pkpWallet.rpcProvider) }), // JsonRpcProvider instance,
  "lit" // signerType
);

4. Use SmartAccountSigner with LightAccount​

We can link the SmartAccountSigner to a LightSmartContractAccount from aa-accounts:

example.ts

import { AlchemyProvider } from "@alchemy/aa-alchemy";
import { LightSmartContractAccount } from "@alchemy/aa-accounts";
import { litSigner } from "./lit";

const chain = sepolia;
const provider = new AlchemyProvider({
  apiKey: "ALCHEMY_API_KEY",
  chain,
  entryPointAddress: "0x...",
}).connect(
  (rpcClient) =>
    new LightSmartContractAccount({
      entryPointAddress: "0x...",
      chain: rpcClient.chain,
      owner: litSigner,
      factoryAddress: "0x...",
      rpcClient,
    })
);

lit.ts

import { WalletClientSigner, type SmartAccountSigner } from "@alchemy/aa-core";
import { LitAbility, LitActionResource } from "@lit-protocol/auth-helpers";
import { LitNodeClient } from "@lit-protocol/lit-node-client";
import { PKPEthersWallet } from "@lit-protocol/pkp-ethers";
import { AuthCallbackParams } from "@lit-protocol/types";
import { createWalletClient, custom } from "viem";
import { polygonMumbai } from "viem/chains";

const API_KEY = "<YOUR API KEY>";
const POLYGON_MUMBAI_RPC_URL = `${polygonMumbai.rpcUrls.alchemy.http[0]}/${API_KEY}`;
const PKP_PUBLIC_KEY = "<YOUR PKP PUBLIC KEY>";

const litNodeClient = new LitNodeClient({
  litNetwork: "cayenne",
  debug: false,
});
await litNodeClient.connect();

const resourceAbilities = [
  {
    resource: new LitActionResource("*"),
    ability: LitAbility.PKPSigning,
  },
];

/**
 * For provisioning keys and setting up authentication methods see documentation below
 * https://developer.litprotocol.com/v2/pkp/minting
 */
const authNeededCallback = async (params: AuthCallbackParams) => {
  const response = await litNodeClient.signSessionKey({
    sessionKey: params.sessionKeyPair,
    statement: params.statement,
    authMethods: [],
    pkpPublicKey: PKP_PUBLIC_KEY,
    expiration: params.expiration,
    resources: params.resources,
    chainId: 1,
  });
  return response.authSig;
};

const sessionSigs = await litNodeClient
  .getSessionSigs({
    chain: "ethereum",
    expiration: new Date(Date.now() + 1000 * 60 * 60 * 24 * 7).toISOString(),
    resourceAbilityRequests: resourceAbilities,
    authNeededCallback,
  })
  .catch((err) => {
    console.log("error while attempting to access session signatures: ", err);
    throw err;
  });

const pkpWallet = new PKPEthersWallet({
  pkpPubKey: PKP_PUBLIC_KEY,
  rpc: POLYGON_MUMBAI_RPC_URL,
  controllerSessionSigs: sessionSigs,
});

// a smart account signer you can use as an owner on ISmartContractAccount
export const litSigner: SmartAccountSigner = new WalletClientSigner(
  createWalletClient({ transport: custom(pkpWallet.rpcProvider) }), // JsonRpcProvider instance,
  "lit" // signerType
);

Next Steps​

Continue learning about Lit's severless signing capabilities.

Explore Account Kit.