## Access Control We will add some access control in our rebase token contract by using OpenZeppelin's `Ownable` and `AccessControl` contracts. First, we will import `Ownable` and `AccessControl`. ```javascript import { ERC20 } from "@openzeppelin/contracts/token/ERC20/ERC20.sol"; import { Ownable } from "@openzeppelin/contracts/access/Ownable.sol"; import { AccessControl } from "@openzeppelin/contracts/access/AccessControl.sol"; ``` Then, we will inherit `Ownable` and `AccessControl` in our contract declaration. ```javascript contract RebaseToken is ERC20, Ownable, AccessControl { ``` Next, we will create a constant byte32 role called `MINT_AND_BURN_ROLE`. ```javascript bytes32 private constant MINT_AND_BURN_ROLE = keccak256("MINT_AND_BURN_ROLE"); ``` In the constructor, we will grant the `MINT_AND_BURN_ROLE` to the message sender. ```javascript constructor() ERC20("Rebase Token", "RBT") Ownable() AccessControl() { _setupRole(DEFAULT_ADMIN_ROLE, msg.sender); _grantRole(MINT_AND_BURN_ROLE, msg.sender); } ``` Now, we will create a function called `grantMintAndBurnRole` which will grant the `MINT_AND_BURN_ROLE` to an address. ```javascript function grantMintAndBurnRole(address account) external onlyRole(DEFAULT_ADMIN_ROLE) { _grantRole(MINT_AND_BURN_ROLE, account); } ``` We will also add the `onlyRole` modifier to our `mint` and `burn` functions. ```javascript function mint(address to, uint256 amount) external onlyRole(MINT_AND_BURN_ROLE) { mintAccruedInterest(to); _mint(to, amount); } function burn(address from, uint256 amount) external onlyRole(MINT_AND_BURN_ROLE) { if (amount == type(uint256).max) { amount = balanceOf(from); } mintAccruedInterest(from); _burn(from, amount); } ``` We will also add the `onlyRole` modifier to our `setInterestRate` function. ```javascript function setInterestRate(uint256 newInterestRate) external onlyRole(DEFAULT_ADMIN_ROLE) { if (newInterestRate <= s_interestRate) { revert RebaseToken__InterestRateCanOnlyDecrease(s_interestRate, newInterestRate); } s_interestRate = newInterestRate; emit InterestRateSet(newInterestRate); } ``` We will also create a function called `grantRole` that will grant the specified role to an account. ```javascript function grantRole(bytes32 role, address account) public virtual onlyRole(getRoleAdmin(role)) { _grantRole(role, account); } ```