Creating a Multi-Sig Wallet in Solidity
Similar to a safe that requires several keys to open, a multi-sig wallet uses multiple signatures. It is a smart contract that saves cryptocurrency and requires several parties' consent to do transactions. Today, we’ll delve into creating a multi-sig wallet using Hardhat, a popular Ethereum development environment. Creating a multi-sig wallet requires significant expertise in smart contract development.
Prerequisites
- A basic understanding of Solidity and Ethereum.
- Node.js is installed on your machine.
- Hardhat is installed globally using the command: npm install -g hardhat.
Setting Up Hardhat
- Starting a New Task: Open your terminal, type npx hardhat, then follow the instructions to start a new project.
- Installing Dependencies: Inside your project directory, install the necessary npm packages with:
- bash
npm install @nomiclabs/hardhat-waffle ethereum-waffle chai @nomiclabs/hardhat-ethers ethers
Writing the Multi-Sig Wallet Smart Contract
- Create a new file called MultiSigWallet.sol in the contracts folder.
- Paste the below code
// SPDX-License-Identifier: MIT pragma solidity ^0.8.20; contract MultiSigWallet { event Deposit(address indexed sender, uint amount, uint balance); event SubmitTransaction( address indexed owner, uint indexed txIndex, address indexed to, uint value, bytes data ); event ConfirmTransaction(address indexed owner, uint indexed txIndex); event RevokeConfirmation(address indexed owner, uint indexed txIndex); event ExecuteTransaction(address indexed owner, uint indexed txIndex); address[] public owners; mapping(address => bool) public isOwner; uint public numConfirmationsRequired; struct Transaction { address to; uint value; bytes data; bool executed; uint numConfirmations; } // mapping from tx index => owner => bool mapping(uint => mapping(address => bool)) public isConfirmed; Transaction[] public transactions; modifier onlyOwner() { require(isOwner[msg.sender], "not owner"); _; } modifier txExists(uint _txIndex) { require(_txIndex < transactions.length, "tx does not exist"); _; } modifier notExecuted(uint _txIndex) { require(!transactions[_txIndex].executed, "tx already executed"); _; } modifier notConfirmed(uint _txIndex) { require(!isConfirmed[_txIndex][msg.sender], "tx already confirmed"); _; } constructor(address[] memory _owners, uint _numConfirmationsRequired) { require(_owners.length > 0, "owners required"); require( _numConfirmationsRequired > 0 && _numConfirmationsRequired <= _owners.length, "invalid number of required confirmations" ); for (uint i = 0; i < _owners.length; i++) { address owner = _owners[i]; require(owner != address(0), "invalid owner"); require(!isOwner[owner], "owner not unique"); isOwner[owner] = true; owners.push(owner); } numConfirmationsRequired = _numConfirmationsRequired; } receive() external payable { emit Deposit(msg.sender, msg.value, address(this).balance); } function submitTransaction( address _to, uint _value, bytes memory _data ) public onlyOwner { uint txIndex = transactions.length; transactions.push( Transaction({ to: _to, value: _value, data: _data, executed: false, numConfirmations: 0 }) ); emit SubmitTransaction(msg.sender, txIndex, _to, _value, _data); } function confirmTransaction( uint _txIndex ) public onlyOwner txExists(_txIndex) notExecuted(_txIndex) notConfirmed(_txIndex) { Transaction storage transaction = transactions[_txIndex]; transaction.numConfirmations += 1; isConfirmed[_txIndex][msg.sender] = true; emit ConfirmTransaction(msg.sender, _txIndex); } function executeTransaction( uint _txIndex ) public onlyOwner txExists(_txIndex) notExecuted(_txIndex) { Transaction storage transaction = transactions[_txIndex]; require( transaction.numConfirmations >= numConfirmationsRequired, "cannot execute tx" ); transaction.executed = true; (bool success, ) = transaction.to.call{value: transaction.value}( transaction.data ); require(success, "tx failed"); emit ExecuteTransaction(msg.sender, _txIndex); } function revokeConfirmation( uint _txIndex ) public onlyOwner txExists(_txIndex) notExecuted(_txIndex) { Transaction storage transaction = transactions[_txIndex]; require(isConfirmed[_txIndex][msg.sender], "tx not confirmed"); transaction.numConfirmations -= 1; isConfirmed[_txIndex][msg.sender] = false; emit RevokeConfirmation(msg.sender, _txIndex); } function getOwners() public view returns (address[] memory) { return owners; } function getTransactionCount() public view returns (uint) { return transactions.length; } function getTransaction( uint _txIndex ) public view returns ( address to, uint value, bytes memory data, bool executed, uint numConfirmations ) { Transaction storage transaction = transactions[_txIndex]; return ( transaction.to, transaction.value, transaction.data, transaction.executed, transaction.numConfirmations ); } }
Compiling Your Smart Contract:
- In your terminal, run npx hardhat compile.
Contract Details
Contract Setup
- Defined using pragma solidity ^0.8.20; to specify the Solidity compiler version.
- contract SecureMultiWallet { … } initiates the contract definition.
Event Definitions
- Events such as FundsDeposited, TransactionSubmitted, TransactionConfirmed, ConfirmationRevoked, and TransactionExecuted are defined to emit logs for significant actions within the contract.
State Variables
- authorizedUsers is an array to track wallet signatories.
- isAuthorized is a mapping to quickly verify if an address is authorized.
- requiredApprovals specifies the number of approvals needed to execute a transaction.
- pendingTransactions is an array to store all proposed transactions.
- hasConfirmed is a nested mapping to keep track of approvals per transaction.
Struct Definition
- PendingTransaction struct is defined to hold information about each proposed transaction.
Modifiers
- onlyAuthorized ensures the function is called by an authorized user.
- transactionExists checks if the transaction ID exists.
- notYetExecuted checks if the transaction has not been executed yet.
- notYetConfirmed checks if the transaction has not already been approved by the caller.
Constructor
The contract is initialised by the constructor with the necessary number of approvals and a list of authorised users.
Fallback Function
- The receive function allows the contract to accept ether and emits a FundsDeposited event.
Transaction Management Functions
- addTransaction: Allows an authorized user to propose a new transaction.
- approveTransaction: Allows an authorized user to approve a proposed transaction.
- runTransaction: Allows an authorized user to execute a transaction once the required number of approvals have been met.
- retractApproval: Allows an authorized user to retract their approval from a proposed transaction.
View Functions
- listUsers: Allows anyone to query the list of authorized users.
- countTransactions: Allows anyone to query the total number of proposed transactions.
- fetchTransaction: Allows anyone to query details of a specific transaction by its ID.
Github: https://github.com/AshishG2/MultiSigSolidity
If you are looking for smart contract development or crypto wallet development, connect with our skilled smart contract developers to get started.