3. Deploying ConfidentialERC20

In this tutorial, you'll learn how to deploy a confidential token contract using Zama's fhEVM. We'll create MyConfidentialERC20.sol to demonstrate the essential features.

Prerequisites

Ensure the following before deploying the smart contract:

• The Zama Plugin installed is installed in the Remix IDE(see Step 1).

• Your wallet is connected to the Sepolia testnet(see Step 2).

Step 1. Setting up the contract file

First, let's create a file for our confidential ERC20 contract:

1. Open the File explorer from the side menu.

2. Navigate to the contracts folder.

3. Click the Create new file icon.

4. Name the file MyConfidentialERC20.sol and press Enter.

Step 2. Writing contract

Step 2.1 Basic contract structure

The foundational structure includes importing Zama's libraries and connecting to Sepolia's fhEVM configuration.

Copy the following code in the MyConfidentialERC20.sol that you just created:

// SPDX-License-Identifier: BSD-3-Clause-Clear

pragma solidity ^0.8.24;

import "fhevm/lib/TFHE.sol";
import "fhevm/config/ZamaFHEVMConfig.sol";

contract MyConfidentialERC20 is SepoliaZamaFHEVMConfig {}

It should appear as follows:

Remix automatically saves any changes as you type. Upon saving, it imports the following libraries:

• TFHE.sol: The core Solidity library of Zama's fhEVM. It enables encrypted data type like euint64, secures encrypted operations, such as addition and comparison and allows access control.

• SepoliaZamaFHEVMConfig: A configuration contract that automatically sets up the required configurations for real-time encrypted operations on the Sepolia testnet.

Step 2.2 Enhancing the functionality

Next, we'll enhance our contract by importing the fhevm-contracts library.

The fhevm-contracts is a Solidity library designed for developers to easily develop confidential smart contracts using fhEVM. It provides:

• Ready-to-use confidential contracts: Pre-built implementations of common token standards with FHE capabilities

• Base contracts: Foundational building blocks for creating custom confidential smart contracts

• Extensions: Additional features and utilities that can be added to base contracts

• Testing utilities: Tools to help test FHE-enabled smart contracts

See more details in the fhEVM-contracts documentation.

The fhevm-contracts library includes the ConfidentialERC20Mintable contract, which is an extention of ConfidentialERC20 with minting capabilities, providing:

• Private token transfers and encrypted balances

• Minting functionality for authorized addresses

• Full ERC20 compatibility

It inherits all base ConfidentialERC20 features while adding secure token creation and distribution capabilities.

To use ConfidentialERC20Mintable contract, simply update your MyConfidentialERC20.sol with the following code:

// SPDX-License-Identifier: BSD-3-Clause-Clear
pragma solidity ^0.8.24;

import "fhevm/lib/TFHE.sol";
import "fhevm/config/ZamaFHEVMConfig.sol";
import "fhevm-contracts/contracts/token/ERC20/extensions/ConfidentialERC20Mintable.sol";

contract MyConfidentialERC20 is SepoliaZamaFHEVMConfig, ConfidentialERC20Mintable {
  constructor(string memory name_, string memory symbol_) ConfidentialERC20Mintable(name_, symbol_, msg.sender) {}
}

It should appear as follows:

Step 3. Compiling the contract

Now the contract is ready, the next step is to compile it:

1. Select MyConfidentialERC20.sol.

2. Go to Solidity compiler in Remix.

3. Click Compile.

If successful, you will see a green checkmark on the Solidity Compiler, indicating "Compilation successful"

Step 4. Deploying the contract

Now the contract is ready to be deployed:

1. Make sure that the envrionment is set up properly

   1. Envrionment: Injected Provider - Metamask

   2. Account: Your wallet address

2. Expand the Deploy section.

3. Fill the constructor parameters:

   • Name: Your token’s name (e.g., "My Private Token").

   • Symbol: Token symbol (e.g., "MPT").

4. Click Transact and confirm the transaction in MetaMask.

Once successfully deployed, your contract will appear under Deployed Contracts. You can also view your contract on Etherscan by clicking the contract address.

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By following these steps, you’ve successfully created and deployed an confidential ERC-20 token using Zama's fhEVM!🎉 Let's see how the transaction works in the next chapter.