---

📃 Read white paper | 📒 Read documentation | 💛 Community support

---

A Solidity library for interacting with an fhEVM blockchain.

Install

# Using npm
npm install fhevm

# Using Yarn
yarn add fhevm

# Using pnpm
pnpm add fhevm

Usage

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

pragma solidity >=0.8.13 <0.8.20;

import "fhevm/lib/TFHE.sol";

contract Counter {
  euint32 counter;

  function add(bytes calldata encryptedValue) public {
    euint32 value = TFHE.asEuint32(encryptedValue);
    counter = TFHE.add(counter, value);
  }

  function getCounter(bytes32 publicKey) returns (bytes memory) {
    return TFHE.reencrypt(counter, publicKey);
  }
}

See our documentation on https://docs.zama.ai/fhevm/solidity/getting_started for more details.

Development Guide

Install dependencies (Solidity libraries and dev tools)

npm install

Note: Solidity files are formatted with prettier.

Generate TFHE lib

npm run codegen

WARNING: Use this command to generate Solidity code and prettier result automatically!

Files that are generated now (can be seen inside codegen/main.ts)

lib/Common.sol
lib/Precompiles.sol
lib/Impl.sol
lib/TFHE.sol
contracts/tests/TFHETestSuiteX.sol
test/tfheOperations/tfheOperations.ts

Tests

The easiest way to understand how to write/dev smart contract and interact with them using fhevmjs is to read and explore the few tests available in this repository.

Fast start

# in one terminal
npm run fhevm:start
# in another terminal
npm i
cp .env.example .env
./scripts/faucet.sh
npm test

Docker

We provide a docker image to spin up a fhEVM node for local development.

npm run fhevm:start
# stop
npm run fhevm:stop

Faucet

To use a ready to use test (only for dev) wallet first, prepare the .env file that contains the mnemonic.

cp .env.example .env

This allows the developer to use a few accounts, each account can get coins:

npm run fhevm:faucet:alice
npm run fhevm:faucet:bob
npm run fhevm:faucet:carol

Run test

npm test

Error: insufficient funds

Ensure the faucet command is succesfull.

Adding new operators

Operators can be defined as data inside codegen/common.ts file and code automatically generates solidity overloads. Test for overloads must be added (or the build doesn't pass) inside codegen/overloadsTests.ts file.

Contributing

There are two ways to contribute to the Zama fhEVM:

• you can open issues to report bugs or typos, or to suggest new ideas
• you can ask to become an official contributor by emailing hello@zama.ai. (becoming an approved contributor involves signing our Contributor License Agreement (CLA)) Only approved contributors can send pull requests, so please make sure to get in touch before you do!

Credits

This library uses several dependencies and we would like to thank the contributors of those libraries.

Need support?

License

This software is distributed under the BSD-3-Clause-Clear license. If you have any questions, please contact us at hello@zama.ai.