fhevm-sdk

React SDK for FHE operations with fhEVM.

Overview

The SDK provides:

• React hooks for FHE encryption/decryption
• Decryption signature management
• FHEVM instance lifecycle
• Storage utilities for signatures

Installation

The SDK is a workspace package:

import { useFHEEncryption, useFHEDecrypt } from 'fhevm-sdk/react';

Exports

fhevm-sdk
├── /core      # Core FHEVM utilities
├── /react     # React hooks
├── /storage   # Storage utilities
└── /types     # Type definitions

React Hooks

useFhevm

Manages FHEVM instance lifecycle:

const { instance, isLoading, error } = useFhevm({
  chainId: 11155111,
  relayerUrl: 'https://relayer.sepolia.zama.ai'
});

useFHEEncryption

Encrypts values for on-chain operations:

const { encrypt, isReady } = useFHEEncryption({ instance });

const encryptedAmount = await encrypt(1000000n);

useFHEDecrypt

Decrypts FHE handles:

const {
  decrypt,
  createSignature,
  hasSignature
} = useFHEDecrypt({ instance });

// Create signature (once per 365 days)
await createSignature([tokenAddress]);

// Decrypt handle
const clearValue = await decrypt(handle);

useInMemoryStorage

Manages signature storage:

const {
  getSignature,
  setSignature,
  clearSignature
} = useInMemoryStorage();

Decryption Signatures

Signatures authorize server-side decryption:

interface DecryptionSignature {
  signature: string;        // Wallet signature
  publicKey: string;        // Ephemeral public key
  privateKey: string;       // Ephemeral private key (NOT wallet key)
  userAddress: string;
  contractAddresses: string[];
  startTimestamp: number;
  durationDays: number;
}

Building

# From monorepo root
pnpm sdk:build

# Watch mode
pnpm sdk:watch

# Run tests
pnpm sdk:test

Dependencies

Package	Purpose
@zama-fhe/relayer-sdk	FHE operations
ethers	Ethereum interaction
idb	IndexedDB storage

Usage Example

import { useFhevm, useFHEEncryption } from 'fhevm-sdk/react';

function PaymentComponent() {
  const { instance } = useFhevm({ chainId: 11155111 });
  const { encrypt, isReady } = useFHEEncryption({ instance });

  const handlePayment = async (amount: bigint) => {
    if (!isReady) return;

    const encrypted = await encrypt(amount);
    // Use encrypted value for transfer
  };

  return (
    <button onClick={() => handlePayment(1000000n)}>
      Pay
    </button>
  );
}