Signing in MPC Core Kit JS SDK

Web3Auth's MPC Core Kit SDK supports both secp256k1 and ed25519 cryptographic curves. The secp256k1 curve enables the retrieval of public keys and the signing of transactions on blockchains compatible with secp256k1, such as Bitcoin and Ethereum. Meanwhile, the ed25519 curve provides the same capabilities for blockchains that support ed25519, ensuring broad compatibility across different blockchain ecosystems.

ECDSA Signature

To sign the transactions for secp256k1 curve, you can utilize the @toruslabs/tss-dkls-lib to instantiate Web3AuthMPCCoreKit with secp256k1 KeyType. To support the secp256k1 curve Web3Auth internally uses the DKLS algorithm to provide the ECDSA signature using threshold protocols.

ECDSA signatures can be used for blockchain applications such as Bitcoin, Ethereum, etc. Let's have an overview of how you can generate ECDSA signature for Ethereum.

Ethereum

As discussed earlier, to generate the ECDSA signature for Ethereum, we will utilize @toruslabs/tss-dkls-lib to instantiate Web3AuthMPCCoreKit with secp256k1 KeyType. This package contains all the necessary functionalities and logic required for TSS signing. Along with that, we'll also use @web3auth/ethereum-mpc-provider which is a helper package. This package will provide a wrapper to sign the message using the partial keys and generate a TSS signature.

Installation

The first step would be to install the helper packages which are required to integrate Web3AuthMPCCoreKit with any EVM-compatible chain.

npm

$ npm install @toruslabs/tss-dkls-lib
$ npm install @web3auth/ethereum-mpc-provider

Yarn

$ yarn add @toruslabs/tss-dkls-lib
$ yarn add @web3auth/ethereum-mpc-provider

pnpm

$ pnpm add @toruslabs/tss-dkls-lib
$ pnpm add @web3auth/ethereum-mpc-provider

Create Web3AuthMPCCoreKit instance

Considering you have already installed the @toruslabs/tss-dkls-lib package, let's use the tssLib to create Web3AuthMPCCoreKit instance.

import { Web3AuthMPCCoreKit, WEB3AUTH_NETWORK } from "@web3auth/mpc-core-kit";
import { tssLib } from "@toruslabs/tss-dkls-lib";

const coreKitInstance = new Web3AuthMPCCoreKit({
  web3AuthClientId: "YOUR_CLIENT_ID",
  web3AuthNetwork: WEB3AUTH_NETWORK.MAINNET,
  manualSync: true, // This is the recommended approach
  tssLib: tssLib,
  storage: window.storage,
});

Create EthereumSigningProvider instance

Once you have the Web3AuthMPCCoreKit instance, you can create the instance of EthereumSigningProvider which will help you to sign the transactions and interact with the blockchain.

import { makeEthereumSigner } from "@web3auth/mpc-core-kit";
import { EthereumSigningProvider } from "@web3auth/ethereum-mpc-provider";

const ethereumProvider = new EthereumSigningProvider({ config: { chainConfig } });
ethereumProvider.setupProvider(makeEthereumSigner(coreKitInstance));

Get a User Account

Once you have an EthereumSigningProvider instance, it can be used as an EIP1193 provider with web3.js, ethers, or viem package. For this documentation, we'll be using web3.js.

We'll first create the Web3 instance using the ethereumProvider. The Web3 instance can be used to get a user's account, perform transactions, sign a message, etc. Read more about supported JSON RPC methods.

import Web3 from "web3";

const web3 = new Web3(provider);

// Get user's EOA address
const address = (await web3.eth.getAccounts())[0];

Sign message

To sign a message, you can use the RPC methods supported. For this documentation, we'll showcase how you can do a personal sign. To learn more about different RPC methods for signing, you can read our EthereumSigningProvider documentation.

const fromAddress = (await web3.eth.getAccounts())[0];
const originalMessage = "YOUR_MESSAGE";

const signedMessage = await web3.eth.personal.sign(originalMessage, fromAddress);

Send Transaction

To send an Ethereum transaction, you can utilize the sendTransaction method. The method will sign the transaction, as well as broadcast the transaction once a valid signature is generated. If you only want to generate a signature, you can use the signTransaction method.

const fromAddress = (await web3.eth.getAccounts())[0];

// Convert 0.0001 ether to wei
const amount = web3.utils.toWei("0.0001");

// This will perform self transfer of 0.0001 ETH.
const receipt = await web3.eth.sendTransaction({
  from: fromAddress,
  to: fromAddress,
  value: amount,
});

Others

The secp256k1 support is not limited to only Ethereum-compatible chains. You can use the SDK with any blockchain ecosystem that supports the secp256k1 curve.

Get PublicKey

To retrieve the secp256k1 publicKey you can use the getPubKey method in Web3AuthMPCCoreKit. The getPubKey will return the compressed public key, you can further use the Point.fromSEC1 to retrive the uncompressed public key.

import { Web3AuthMPCCoreKit, WEB3AUTH_NETWORK } from "@web3auth/mpc-core-kit";
import { tssLib } from "@toruslabs/tss-dkls-lib";

const coreKitInstance = new Web3AuthMPCCoreKit({
  web3AuthClientId: "YOUR_CLIENT_ID",
  web3AuthNetwork: WEB3AUTH_NETWORK.MAINNET,
  manualSync: true, // This is the recommended approach
  tssLib: tssLib,
  storage: window.storage,
});

// Compressed pubKey
const pubKey = coreKitInstance.getPubKey();

// Uncompressed pubKey
const pubKeyPoint = Point.fromSEC1(secp256k1, pubKey.toString("hex"));
const uncompressedPubKey = pubKeyPoint.toSEC1(secp256k1).subarray(1);

Signing

To sign the transaction for secp256k1 curve, you can use the sign method. The method will return the ECDSA signature.

const msg = Buffer.from("Welcome to Web3Auth");

// Returns the ECDSA signature bytes.
const signature = coreKitInstance.sign(msg);

EdDSA Signature

Along with ECDSA signature, Web3AuthMPCCoreKit also supports ed25519 curve to generate EdDSA signatures. To sign the transactions for ed25519 curve, you can utilize the @toruslabs/tss-frost-lib to instantiate Web3AuthMPCCoreKit with ed25519 KeyType. To support the ed25519 curve Web3Auth internally uses the FROST algorithm to provide the EdDSA sginature using threshold protocols.

EdDSA signatures can be used for blockchain applications such as Solana, Aptos, etc. Let's have an overview of how you can generate EdDSA signature for Solana.

Solana

As discussed earlier, to generate the EdDSA signature for Solana, we will utilize @toruslabs/tss-frost-lib to instantiate Web3AuthMPCCoreKit with ed25519 KeyType. This package contains all the necessary functionalities and logic required for TSS signing. Along with that, we'll also use @solana/web3.js package. This package will provide a wrapper to generate the transaction bytes, verify the message, and interact with Solana.

Installation

The first step would be to install the helper packages which are required to integrate Web3AuthMPCCoreKit with Solana chain.

$ npm install @solana/web3.js
$ npm install @toruslabs/tss-frost-lib

Create Web3AuthMPCCoreKit instance

Considering you have already installed the @toruslabs/tss-frost-lib package, let's use the tssLib to create Web3AuthMPCCoreKit instance.

import { Web3AuthMPCCoreKit, WEB3AUTH_NETWORK } from "@web3auth/mpc-core-kit";
import { tssLib } from "@toruslabs/tss-frost-lib";

const coreKitInstance = new Web3AuthMPCCoreKit({
  web3AuthClientId: "YOUR_CLIENT_ID",
  web3AuthNetwork: WEB3AUTH_NETWORK.MAINNET,
  manualSync: true, // This is the recommended approach
  tssLib: tssLib,
  storage: window.storage,
});

Get a User Account

Once you have an Web3AuthMPCCoreKit instance, it can be used as along with solana/web3.js package.

To generate the Solana EOA address, you can use the getPubKeyEd25519 method to retrieve the ed25519 curve compatible pubKey. Since solana uses the base58 enocded address, you can simply encode pubKey with base58 to get the user's EOA address.

import { base58 } from "@scure/base";

const address = base58.encode(Uint8Array.from(coreKitInstance.getPubKeyEd25519()));

If you want to verify that the public key is on ed25519 curve, you can create a new PublicKey instance using the generated address. Once you have the PublicKey instance, you can use the isOnCurve static method to verify the curve.

import { PublicKey } from "@solana/web3.js";

const publicKey = new PublicKey(address);

// Returns whether the public is on ed25519 curve
const isValidAddress = PublicKey.isOnCurve(publicKey.toBytes());

Sign a message

Signing a message for Solana is pretty straight forward. You can simply use the sign method to generate the EdDSA signature.

const msg = Buffer.from("Welcome to Web3Auth");
const sig = await this.coreKitInstance.sign(msg);

Sign a Transaction

To sign a Solana transaction, you can use Transaction class to get a buffer of the transaction data to sign, and add geerated signature to the transaction. The public key must correspond to either the fee payer or a signer account in the transaction instructions.

import {
  Connection,
  LAMPORTS_PER_SOL,
  PublicKey,
  clusterApiUrl,
  SystemProgram,
  Transaction,
} from "@solana/web3.js";

const connection = new Connection(clusterApiUrl("devnet"), "confirmed");

const lamportsToSend = 1_000_000;
const getRecentBlockhash = await this.connection.getLatestBlockhash("confirmed");

const transferTransaction = new Transaction().add(
  // Self transfer tokens
  SystemProgram.transfer({
    fromPubkey: this.publicKey,
    toPubkey: this.publicKey,
    lamports: lamportsToSend,
  }),
);

transferTransaction.recentBlockhash = getRecentBlockhash.blockhash;
transferTransaction.feePayer = this.publicKey;

// Sign the serialize message
const sig = await this.coreKitInstance.sign(transferTransaction.serializeMessage());

// Append the signature to the transaction
transferTransaction.addSignature(this.publicKey, sig);

// Signature of the transaction in wire format which can be broadcasted on Solana chain.
const transferTransactionSignature = transferTransaction.serialize();

To broadcast the signed transaction, you can utilize the Connection.sendRawTransaction method.

// Returns the hash, for connection and transferTransactionSignature, check above
// code snippets
let hash = await connection.sendRawTransaction(transferTransactionSignature);

Others

The ed25519 support is not limited to only Solana chain. You can use the SDK with any blockchain ecosystem that supports the ed25519 curve.

Get PublicKey

To retrieve the ed25519 publicKey you can use the getPubKeyEd25519 method in Web3AuthMPCCoreKit.

import { Web3AuthMPCCoreKit, WEB3AUTH_NETWORK } from "@web3auth/mpc-core-kit";
import { tssLib } from "@toruslabs/tss-frost-lib";

const coreKitInstance = new Web3AuthMPCCoreKit({
  web3AuthClientId: "YOUR_CLIENT_ID",
  web3AuthNetwork: WEB3AUTH_NETWORK.MAINNET,
  manualSync: true, // This is the recommended approach
  tssLib: tssLib,
  storage: window.storage,
});

const pubKey = coreKitInstance.getPubKeyEd25519();

Signing

To sign the transaction or a message for ed25519 curve, you can use the sign method. The method will return the EdDSA signature.

const msg = Buffer.from("Welcome to Web3Auth");

// Returns the EdDSA signature bytes.
const signature = coreKitInstance.sign(msg);