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# Account Abstraction
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ERC-4337 compliant smart contract wallets with modular authentication, transaction batching, and paymaster integration for flexible account management.
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## Capabilities
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### Account Contract
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Core ERC-4337 account implementation with modular signature validation and execution.
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```solidity { .api }
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/**
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 * ERC-4337 Account implementation with ERC-1271 signature validation
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 */
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contract Account is Context, IERC165, IERC1271, IAccount, Ownable, UUPSUpgradeable {
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    constructor(IEntryPoint anEntryPoint);
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    function validateUserOp(PackedUserOperation calldata userOp, bytes32 userOpHash, uint256 missingAccountFunds) external virtual returns (uint256 validationData);
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    function executeUserOp(PackedUserOperation calldata userOp, bytes32 userOpHash) external virtual;
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    function isValidSignature(bytes32 hash, bytes calldata signature) external view virtual returns (bytes4 magicValue);
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    function entryPoint() public view virtual returns (IEntryPoint);
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    function execute(address target, uint256 value, bytes calldata data) external virtual requireFromEntryPointOrOwner;
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    function executeBatch(address[] calldata targets, uint256[] calldata values, bytes[] calldata data) external virtual requireFromEntryPointOrOwner;
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    function proxiableUUID() external view virtual override notDelegated returns (bytes32);
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    function upgradeToAndCall(address newImplementation, bytes memory data) public payable virtual onlyProxy;
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}
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```
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**Usage Examples:**
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```solidity
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import "@openzeppelin/contracts/account/Account.sol";
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contract MyAccount is Account {
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    constructor(IEntryPoint anEntryPoint, address initialOwner) 
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        Account(anEntryPoint) 
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        Ownable(initialOwner) 
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    {}
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    // Execute a transaction
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    function executeTransaction(address target, uint256 value, bytes calldata data) external {
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        execute(target, value, data);
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    }
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    // Execute multiple transactions
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    function executeBatch(
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        address[] calldata targets, 
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        uint256[] calldata values, 
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        bytes[] calldata data
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    ) external {
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        executeBatch(targets, values, data);
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    }
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}
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```
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### Account Management Utilities
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Utilities for account deployment, validation, and management.
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```solidity { .api }
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/**
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 * Signature validation utilities for Account contracts
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 */
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library AccountUtils {
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    function isValidSignature(address account, bytes32 hash, bytes calldata signature) internal view returns (bool);
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    function validateSignature(address account, bytes32 hash, bytes calldata signature) internal view;
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}
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```
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### Account Extensions
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Extensions for enhanced account functionality.
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#### AccountMultiSig Extension
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Multi-signature functionality for account contracts.
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```solidity { .api }
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/**
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 * Multi-signature extension for Account contracts
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 */
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abstract contract AccountMultiSig is Account {
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    function addOwner(address newOwner) external virtual onlyOwner;
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    function removeOwner(address owner) external virtual onlyOwner;
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    function changeRequirement(uint256 required) external virtual onlyOwner;
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    function getOwners() external view virtual returns (address[] memory);
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    function getThreshold() external view virtual returns (uint256);
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    function isOwner(address owner) external view virtual returns (bool);
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}
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```
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## Types
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```solidity { .api }
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/**
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 * ERC-4337 User Operation structure
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 */
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struct PackedUserOperation {
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    address sender;
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    uint256 nonce;
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    bytes initCode;
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    bytes callData;
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    bytes32 accountGasLimits;
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    uint256 preVerificationGas;
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    bytes32 gasFees;
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    bytes paymasterAndData;
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    bytes signature;
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}
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/**
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 * Account validation result
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 */
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struct ValidationData {
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    address aggregator;
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    uint48 validAfter;
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    uint48 validUntil;
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}
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/**
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 * ERC-4337 Entry Point interface
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 */
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interface IEntryPoint {
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    function handleOps(PackedUserOperation[] calldata ops, address payable beneficiary) external;
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    function handleAggregatedOps(UserOpsPerAggregator[] calldata opsPerAggregator, address payable beneficiary) external;
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    function depositTo(address account) external payable;
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    function balanceOf(address account) external view returns (uint256);
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    function withdrawTo(address payable withdrawAddress, uint256 withdrawAmount) external;
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}
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/**
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 * Account interface for ERC-4337 compliance
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 */
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interface IAccount {
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    function validateUserOp(PackedUserOperation calldata userOp, bytes32 userOpHash, uint256 missingAccountFunds) external returns (uint256 validationData);
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}
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/**
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 * Account modifiers and validation
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 */
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error AccountUnauthorized();
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error AccountInvalidSignature();
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error AccountInvalidUserOp();
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```