About

What is fhEVM

fhEVM is a technology that enables confidential smart contracts on the EVM using fully homomorphic encryption (FHE).

Thanks to a breakthrough in homomorphic encryption, Zama’s fhEVM makes it possible to run confidential smart contracts on encrypted data, guaranteeing both confidentiality and composability with:

• End-to-end encryption of transactions and state: Data included in transactions is encrypted and never visible to anyone.
• Composability and data availability on-chain: States are updated while remaining encrypted at all times.
• No impact on existing dapps and state: Encrypted state co-exists alongside public one, and doesn't impact existing dapps.

Main features

• Solidity integration: fhEVM contracts are simple solidity contracts that are built using traditional solidity toolchains.
• Simple developer experience: Developers can use the euint data types to mark which part of their contracts should be private.
• Programmable privacy: All the logic for access control of encrypted states is defined by developers in their smart contracts.
• High precision encrypted integers : Up to 256 bits of precision for integers
• Full range of operators : All typical operators are available: +, -, *, /, <, >, ==, …
• Encrypted if-else conditionals : Check conditions on encrypted states
• On-chain PRNG : Generate secure randomness without using oracles
• Configurable decryption : Threshold, centralized or KMS decryption
• Unbounded compute Depth : Unlimited consecutive FHE operations

Learn more about fhEVM features in the documentation.

Use cases

fhEVM is built for developers to write confidential smart contracts without learning cryptography. Leveraging fhEVM, you can unlock a myriad of new use cases such as DeFI, gaming, and more. For instance:

• Tokenization: Swap tokens and RWAs on-chain without others seeing the amounts.
• Blind auctions: Bid on items without revealing the amount or the winner.
• On-chain games: Keep moves, selections, cards, or items hidden until ready to reveal.
• Confidential voting: Prevents bribery and blackmailing by keeping votes private.
• Encrypted DIDs: Store identities on-chain and generate attestations without ZK.
• Private transfers: Keep balances and amounts private, without using mixers.

Learn more use cases in the list of examples.

Table of Contents

• Getting Started
  • Installation
  • A Simple Example
• Resources
  • White paper Demos
  • Documentation
  • Blockchain Implementation
• Working with fhEVM
  • Developer guide
  • Citations
  • Contributing
  • License
• Support

Getting Started

Installation

# Using npm
npm install fhevm

# Using Yarn
yarn add fhevm

# Using pnpm
pnpm add fhevm

A Simple Example

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

pragma solidity ^0.8.24;

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

contract Counter is SepoliaZamaFHEVMConfig {
  euint8 internal counter;

  constructor() {
    counter = TFHE.asEuint8(0);
    TFHE.allowThis(counter);
  }

  function add(einput valueInput, bytes calldata inputProof) public {
    euint8 value = TFHE.asEuint8(valueInput, inputProof);
    counter = TFHE.add(counter, value);
    TFHE.allowThis(counter);
  }
}

More examples are available here.

[!Note] > Zama 5-Question Developer Survey

We want to hear from you! Take 1 minute to share your thoughts and helping us enhance our documentation and libraries. 👉 Click here to participate.

Resources

White Paper

Gain insights into the technology powering fhEVM with our in-depth white paper:
👉 Confidential EVM Smart Contracts using Fully Homomorphic Encryption

Demos and Tutorials

Access a curated collection of demos and step-by-step tutorials to guide your development journey: 🔗 Visit the Tutorials Page

Documentation

Master fhEVM and build smart contracts using these resources:

• 📘 Comprehensive fhEVM Documentation
  Dive deep into Zama's detailed guide for utilizing the full potential of fhEVM.

• 🤖 ZAMA Solidity Developer (Modified ChatGPT Model)
  Accelerate your smart contract development with AI-powered assistance.

Development templates

Start building faster with pre-configured templates tailored for various frameworks:

Smart Contracts

• 🔧 Hardhat Template
  Smart contracts testing and development <- primary entry point for developers wanting to develop smart contracts on fhEVM
• 💻 fhEVM Contracts
  Library of standardized fhEVM contracts.

Frontend frameworks

• 🌐 React.js Template
  Simplify your FHE dApp development with a clean and optimized React.js template.
• ⚡ Next.js Template
  Build server-rendered, scalable dApps with FHE support using this Next.js template.
• 🖼️ Vue.js Template
  Create modular, responsive dApps with FHE capabilities using Vue.js.

🚀 Kickstart Your Project Today!

Leverage these templates to accelerate your development process and bring your ideas to life faster.

Blockchain Implementation

To integrate fhevm-go into any EVM-based blockchain, you can follow the Integration Guide.

Working with fhEVM

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

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.

Citations

To cite fhEVM or the whitepaper in academic papers, please use the following entries:

@Misc{fhEVM,
title={{Confidential EVM Smart Contracts using Fully Homomorphic Encryption}},
author={Zama},
year={2024},
note={\url{https://github.com/zama-ai/fhevm}},
}

@techreport{fhEVM,
author = "Zama",
title = "Confidential EVM Smart Contracts using Fully Homomorphic Encryption",
institution = "Zama",
year = "2024"
}

Contributing

There are two ways to contribute to the Zama fhEVM:

• Open issues to report bugs and typos, or to suggest new ideas
• Request to become an official contributor by emailing [email protected].

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!

License

This software is distributed under the BSD-3-Clause-Clear license. Read this for more details.

FAQ

Is Zama’s technology free to use?

Zama’s libraries are free to use under the BSD 3-Clause Clear license only for development, research, prototyping, and experimentation purposes. However, for any commercial use of Zama's open source code, companies must purchase Zama’s commercial patent license.

Everything we do is open source and we are very transparent on what it means for our users, you can read more about how we monetize our open source products at Zama in this blog post.

What do I need to do if I want to use Zama’s technology for commercial purposes?

To commercially use Zama’s technology you need to be granted Zama’s patent license. Please contact us at [email protected] for more information.

Do you file IP on your technology?

Yes, all Zama’s technologies are patented.

Can you customize a solution for my specific use case?

We are open to collaborating and advancing the FHE space with our partners. If you have specific needs, please email us at [email protected].

Support

🌟 If you find this project helpful or interesting, please consider giving it a star on GitHub! Your support helps to grow the community and motivates further development.