Cofhejs

Aspect	Description
Type	Typescript Library
Function	Provides functionality to initialize TFHE, generate and manage permits, encrypt input data, and read encrypted data.
Responsibilities	Handle primary interactions with FHE enabled contracts and the CoFHE Co-Processor.

Cofhejs is the JavaScript library that provides client-side functionality for interacting with CoFHE smart contracts. It handles encryption, decryption, and communication with the blockchain.

Installation

To get started with Cofhejs, you need to install it as a dependency in your JavaScript project. You can do this using npm (Node Package Manager) or Yarn. Open your terminal and navigate to your project's directory, then run the following:

yarn

yarn add cofhejs

npm

npm install cofhejs

pnpm

pnpm add cofhejs

Note: For more information on getting started, take a look at the Cofhejs getting started guide.

Key Features

Initialization

const { cofhejs } = require('cofhejs/node')
const { ethers } = require('ethers')

// initialize your web3 provider
const provider = new ethers.JsonRpcProvider('http://127.0.0.1:42069')
const wallet = new ethers.Wallet(PRIVATE_KEY, provider)

// initialize cofhejs Client with ethers (it also supports viem)
await cofhejs.initializeWithEthers({
	ethersProvider: provider,
	ethersSigner: wallet,
	environment: 'TESTNET',
})

Note: For more information on getting started, take a look at the Cofhejs getting started guide.

• Client-side encryption/decryption

const logState = (state: EncryptStep) => {
    console.log(`Log Encrypt State :: ${state}`);
};

// This will encrypt only the encrypted values (total 4 in this case)
const encryptedValues = await cofhejs.encrypt(logState, [
    { a: Encryptable.bool(false), b: Encryptable.uint64(10n), c: "hello" },
    ["hello", 20n, Encryptable.address(contractAddress)],
    Encryptable.uint8("10"),
] as const);

const contract = new ethers.Contract(CONTRACT_ADDRESS, CONTRACT_ABI, wallet);
// Use the encrypted value of 10n
const tx = await contract.add(encryptedValues.data[1]);

Cofhejs exposes a function encrypt that takes any data type, any Encryptable values within the input are extracted into an array, packed, and verified using a ZK Proof of Encryption. For more information on this process and how it works under the hood take a look at the encryption data flow.

• Key management

Cofhejs automatically fetches two keys from CoFHE, the FHE public key and a CRS. These keys are used during the encrypt flow, which prepares encrypted inputs to be used as transaction parameters.

Note: Read more about encryption here

• Permits

Permits allow users to access their encrypted data by authenticating the user with an EIP712 signature. Permits can be managed within Cofhejs, or they can be managed within a client dApp directly by using the exposed Permit class.

Note: Read more about permits here

• Reading encrypted data

On-chain FHE operations are symbolic, meaning that an euint64 is a handle to an encrypted number that lives on the Fhenix Mainnet chain. It is possible to read the encrypted data through an off-chain call by using cofhejs.unseal() like so:

const resultHandle = await contract.getSomeEncryptedUint32()
const unsealed = await cofhejs.unseal(resultHandle, FheTypes.Uint32)

You can read more about unsealing and the underlying process in the unsealing data-flow page, and you can read more about cofhejs.unseal usage here.