zktubewind / zksync-sdk-dart

ZKSync SDK for Flutter/Dart

title	disqus
ZkSync Dart SDK	hackmd

ZkSync SDK

Table of Contents

[TOC]

Getting started

1. Connect to the zkSync network.
2. Deposit assets from Ethereum into zkSync.
3. Make transfers.
4. Withdraw funds back to Ethereum mainnet (or testnet).

Adding dependencies

Using this SDK requires precompiled binary of zkSync cryptography implementation. Please download directly from official repo

Then just add this sdk as a dependency into your app build configuration.

name: <your_app_name>
...

environment:
  sdk: '>=2.10.0 <3.0.0'

dependencies:
  zksync: ^0.0.1
  ...

Native library is precompiled for the following platforms:

Desktop

• Linux x86_64
• OSX x86_64 (MacOS 11 BigSur included)
• Windows x86_64

Android

• Arm64-v8a
• Armeabi-v7a
• x86
• x86_64

iOS

• i386
• x86_64

Imports

Client library is divided into three separate packages. Just add required into imports block of your main file;

import 'package:zksync/client.dart'; // ZkSync RPC/REST client
import 'package:zksync/credentials.dart'; // Crypto Credentials
import 'package:zksync/zksync.dart'; // Main Wallet

Creating signers

All messages in zkSync network must be signed by the private key. There are two keys required: Level 1 (L1) for Ethereum and Level 2 (L2) for zkSync network.

To operate in zkSync network you need to create ZkSigner instance first. There are few ways to create it:

Using seed bytes (like MNEMONIC phrase) with the length >= 32

final zkSigner = ZksSigner.seed(SEED);

Using raw private key

final rawPrivateKey = hex.decode('0x...');

final zkSigner = ZksSigner.raw(rawPrivateKey);

Using raw private key in hex

final zkSigner = ZksSigner.hex('0x...');

Using EthSigner (explained below). The private key used by ZkSigner is implicitly derived by signing a special message with Ethereum L1 key.

final ethSigner = ...;

final zkSigner = await ZksSigher.fromEthSigner(ethSigner, ChainId.Rinkeby);

---

To interract with Ethereum L1 chain (to make a Deposit or Withdraw funds), you'll need EthSigner instance. It can be instantiated in several different ways:

Using raw private key in hex

final ethSigner = EthSigner.hex(privateKey, chainId: ChainId.Rinkeby.getChainId());

Using raw private key

final rawPrivateKey = hex.decode('0x...');

final ethSigner = EthSigner.raw(privateKey);

Using Credentials from Web3dart

import 'package:web3dart/web3dart.dart' as web3;

final credentials = web3.EthPrivateKey.fromHex(hexKey);

Connecting to zkSync network

In order to interact with both zkSync and Ethereum networks you'll need to create providers and provide endpoints to blockchain nodes

zkSync client

This SDK has predefined URLs for the following networks ChainId.Mainnet, ChainId.Ropsten, ChainId.Rinkeby that are officially supported by MatterLabs. Also you can use local node for testing ChainId.Localhost or simply set endpoint to http://127.0.0.1:3030

final zksync = ZkSyncClient.fromChainId(ChainId.Rinkeby);

You can also create ZkSyncClient with any custom endpoint URL

import 'package:http/http.dart';

final zksync = ZkSyncClient('http://localhost:3030', Client());

Ethereum client

For onchain operations in Ethereum network you can use EthereumClient

final ethSigner = ...;

final ethereum =
      EthereumClient('http://localhost:8545', ethSigner.credentials, ChainId.Rinkeby);

Creating a Wallet

To control and operate with your account in zkSync you can use the Wallet. It can sign transactions with the key stored in ZkSigner and EthSigner, then send signed transactions into zkSync network using ZkSyncClient.

final ethSigner = ...;
final zkSigner = ...;
final ethClient = ...;
final zksClient = ...;

final wallet = Wallet(zksClient, ethClient, zkSigner, ethSigner);

Depositing assets from Ethereum into zkSync

In order to deposit assets from Ethereum network into zkSync please use the following sequence:

final ethSigner = ...;
final ethClient = ...;

final receiver = await ethSigner.extractAddress();

final depositTx = await ethClient.deposit(Token.eth,
      EtherAmount.fromUnitAndValue(EtherUnit.ether, 1).getInWei, receiver);

Checking your zkSync balance

In order to check your account balance in zkSync network please use the following commands:

final wallet = ...;

final state = await wallet.getState();
final balance = state.commited.balances['ETH'];

Unlocking zkSync account

In order to make any transactions in zkSync network, you'll need to register your ZkSigner's public key first. Please use the following command to do this:

final zkSigner = ...;
final wallet = ...;

final authTx = await wallet.setSigningKey(
      ZksPubkeyHash.fromHex(zkSigner.publicKeyHash),
      token: Token.eth);
print(authTx);

Transfering funds in zkSync

After funds Deposited and account Unlocked, you can transfer funds inside zkSync network.

Please note, that it is possible to send assets within zkSync to any Ethereum address, without preliminary registration in zkSync!

In the example below, we're going to transfer 0.1 ETH

final wallet = ...;

final receiver =
      EthereumAddress.fromHex('0x...');

final tx = await wallet.transfer(
      receiver, EtherAmount.fromUnitAndValue(EtherUnit.eth, 0.1).getInWei,
      token: Token.eth);
print(tx);

Withdrawing funds back to Ethereum

All your funds can be withdrawn back to any yours account in Ethereum. Please use the following commands:

final wallet = ...;

final withdrawTx = await wallet.withdraw(
      receiver, EtherAmount.fromUnitAndValue(EtherUnit.eth, 0.5).getInWei,
      token: Token.eth);
print(withdrawTx);

Assets will be withdrawn to the target address after a zero-knowledge proof of zkSync block with this operation is generated and verified by the mainnet contract (which usually takes about 2-10 min).

Forced and Full exit

Also you can force full withdrawal of all your funds back to your onchain account with a single command:

On zkSync

final wallet = ...;

final exitTx = await wallet.forcedExit(receiver, token: Token.eth);
print(exitTx);

On Ethereum (onchain)

final ethClient = ...;
final wallet = ...;

final exitTx =
      await ethClient.fullExit(Token.eth, await wallet.getAccountId());
print(exitTx);