Skip to main content

Hands-on fhEVM

This hands-on guide will walk you through understanding, setting up, and working with fhEVM to develop encrypted smart contracts and test them on fhEVM network.

What You’ll Learn​

  • Basics of fhEVM and its architecture.
  • Setting up a local fhEVM development environment.
  • Writing, compiling, and deploying FHE-enabled Solidity contracts.
  • Testing encrypted contract interactions.

1. Understanding fhEVM​

fhEVM is a privacy-first smart contract platform that allows computations on encrypted data without decryption. This ensures on-chain privacy while maintaining verifiability and interoperability.

Core Principles​

  1. Security: No compromise on blockchain security.
  2. Public Verifiability: Confidential yet verifiable computations.
  3. Developer-Friendly: Familiar Solidity tools.
  4. Composability: Interoperable confidential and public contracts.

Key Features​

  • Encrypted Data Types: ebool, euintX, eaddress, ebytesX, etc.
  • Homomorphic Computation: Arithmetic on encrypted numbers.
  • Confidential Transactions: Data remains encrypted even on-chain.
  • EVM-Compatible: Supports Solidity with added FHE functionalities.

Encrypted Data Types​

fhEVM introduces special encrypted types for secure computations:

  • Booleans: ebool
  • Integers: euint4, euint8, ... euint256
  • Addresses: eaddress
  • Bytes: ebytes64, ebytes128, ebytes256
  • Inputs: einput

Type Casting​

fhEVM provides utility functions to convert between encrypted types:

  • TFHE.asEbool(value): Converts a boolean to an encrypted boolean.
  • TFHE.asEuintX(value): Converts an integer to an encrypted integer.
  • TFHE.asEaddress(value): Converts an address to an encrypted address.

fhEVM empowers secure and efficient computation on encrypted data while preserving blockchain functionality.

2. fhEVM Architecture​

Core Components​

fhEVM consists of several interdependent components:

  • Smart Contracts: Interact with encrypted data to execute logic securely on the blockchain.
  • fhEVM-native: On-chain processing that handles homomorphic computations on ciphertexts using evaluation keys.
  • Key Management System (KMS): Safeguards private keys for decryption and re-encryption processes.
  • Gateway: Acts as a bridge between the blockchain and the KMS, enabling secure operations like decryption and re-encryption.
  • Connector: A service that connects the gateway to the KMS.
  • Gateway Store: A service that stores ciphertexts.
  • fhEVM.js Library: Facilitates client-side interactions such as encryption, decryption, and re-encryption.

End-to-End Confidentiality​

fhEVM ensures that:

  • Plaintext data is never exposed during processing or transmission.
  • Homomorphic computations enable complex operations on encrypted data.
  • Secure re-encryption allows sharing and interoperability without compromising privacy.

This tightly integrated architecture supports decentralized applications (dApps) requiring privacy-preserving operations, paving the way for more secure and trustless systems.

For more detailed insights, you can refer to the official documentation by Zama.

What's Next?​

Now that you understand the fhEVM architecture, let's set up an fhEVM network. ➡ Move on to Network Setup to learn how to proceed.