JS on WASM API

This document outlines how to use the TFHE-rs WebAssembly (WASM) client API for key generation, encryption, and decryption, providing setup examples for Node.js and web browsers.

TFHE-rs supports WASM client API, which includes functionality for key generation, encryption, and decryption. However, it does not support FHE computations.

TFHE-rs supports 3 WASM targets:

• Node.js: For use in Node.js applications or packages

• Web: For use in web browsers

• Web-parallel: For use in web browsers with multi-threading support

The core of the API remains the same, requiring only minor changes in the initialization functions.

Node.js

Example:

const {
    init_panic_hook,
    ShortintParametersName,
    ShortintParameters,
    TfheClientKey,
    TfheCompactPublicKey,
    TfheCompressedServerKey,
    TfheConfigBuilder,
    CompactFheUint32List
} = require("./pkg/tfhe.js");

function fhe_uint32_example() {
    // Makes it so that if a rust thread panics,
    // the error message will be displayed in the console
    init_panic_hook();

    const block_params = new ShortintParameters(ShortintParametersName.PARAM_SMALL_MESSAGE_2_CARRY_2_COMPACT_PK);
    let config = TfheConfigBuilder.default()
        .build();

    let clientKey = TfheClientKey.generate(config);
    let compressedServerKey = TfheCompressedServerKey.new(clientKey);
    let publicKey = TfheCompactPublicKey.new(clientKey);

    let values = [0, 1, 2394, U32_MAX];
    let compact_list = CompactFheUint32List.encrypt_with_compact_public_key(values, publicKey);

    let serialized_list = compact_list.serialize();
    let deserialized_list = CompactFheUint32List.deserialize(serialized_list);
    let encrypted_list = deserialized_list.expand();
    assert.deepStrictEqual(encrypted_list.length, values.length);

    for (let i = 0; i < values.length; i++)
    {
        let decrypted = encrypted_list[i].decrypt(clientKey);
        assert.deepStrictEqual(decrypted, values[i]);
    }
}

Web

When using the Web WASM target, you should call an additional init function. With parallelism enabled, you need to call another additional initThreadPool function.

Example:

import init, {
    initThreadPool, // only available with parallelism
    init_panic_hook,
    ShortintParametersName,
    ShortintParameters,
    TfheClientKey,
    TfhePublicKey,
} from "./pkg/tfhe.js";

async function example() {
    await init()
    await initThreadPool(navigator.hardwareConcurrency);
    await init_panic_hook();

    const block_params = new ShortintParameters(ShortintParametersName.PARAM_SMALL_MESSAGE_2_CARRY_2_COMPACT_PK);
    // ....
}

Compiling the WASM API

Use the provided Makefile in the TFHE-rs repository to compile for the desired target:

• make build_node_js_api for the Node.js API

• make build_web_js_api for the browser API

• make build_web_js_api_parallel for the browser API with parallelism

The compiled WASM packages are located in tfhe/pkg.

The browser API and the Node.js API are available as npm packages. Using npm i tfhe for the browser API and npm i node-tfhe for the Node.js API.

Using the JS on WASM API

TFHE-rs uses WASM to provide a JavaScript (JS) binding to the client-side primitives, like key generation and encryption within the Boolean and shortint modules.

Currently, there are several limitations. Due to a lack of threading support in WASM, key generation can be too slow to be practical for bigger parameter sets.

Some parameter sets lead to the FHE keys exceeding the 2GB memory limit of WASM, making these parameter sets virtually unusable.

First steps using TFHE-rs JS on WASM API

Setting up TFHE-rs JS on WASM API for Node.js programs.

To build the JS on WASM bindings for TFHE-rs, install wasm-pack and the necessary rust toolchain. Cone the TFHE-rs repository and build using the following commands (this will build using the default branch, you can check out a specific tag depending on your requirements):

$ git clone https://github.com/zama-ai/tfhe-rs.git
Cloning into 'tfhe-rs'...
...
Resolving deltas: 100% (3866/3866), done.
$ cd tfhe-rs
$ cd tfhe
$ rustup run wasm-pack build --release --target=nodejs --features=boolean-client-js-wasm-api,shortint-client-js-wasm-api
[INFO]: Compiling to Wasm...
...
[INFO]: :-) Your wasm pkg is ready to publish at ...

The command above targets Node.js. To generate a binding for a web browser, use --target=web. However, this tutorial does not cover that particular use case.

Both Boolean and shortint features are enabled here, but it's possible to use them individually.

After the build, a new directory pkg is available in the tfhe directory.

$ ls pkg
LICENSE  index.html  package.json  tfhe.d.ts  tfhe.js  tfhe_bg.txt  tfhe_bg.wasm  tfhe_bg.wasm.d.ts
$

Commented code to generate keys for shortint and encrypt a ciphertext

Make sure to update the path of the required clause in the example below to match the location of the TFHE package that was just built.

// Here import assert to check the decryption went well and panic otherwise
const assert = require('node:assert').strict;
// Import the Shortint module from the TFHE-rs package generated earlier
const { Shortint } = require("/path/to/built/tfhe/pkg");

function shortint_example() {
    // Get pre-defined parameters from the shortint module to manage messages with 4 bits of useful
    // information in total (2 bits of "message" and 2 bits of "carry")
    let params = Shortint.get_parameters(2, 2);
    // Create a new secret ClientKey, this must not be shared
    console.log("Generating client keys...")
    let cks = Shortint.new_client_key(params);
    // Encrypt 3 in a ciphertext
    console.log("Encrypting 3...")
    let ct = Shortint.encrypt(cks, BigInt(3));

    // Demonstrate ClientKey serialization (for example saving it on disk on the user device)
    let serialized_cks = Shortint.serialize_client_key(cks);
    // Deserialization
    let deserialized_cks = Shortint.deserialize_client_key(serialized_cks);

    // Demonstrate ciphertext serialization to send over the network
    let serialized_ct = Shortint.serialize_ciphertext(ct);
    // Deserialize a ciphertext received over the network for example
    let deserialized_ct = Shortint.deserialize_ciphertext(serialized_ct);

    // Decrypt with the deserialized objects
    console.log("Decrypting ciphertext...")
    let decrypted = Shortint.decrypt(deserialized_cks, deserialized_ct);
    // Check decryption works as expected
    assert.deepStrictEqual(decrypted, BigInt(3));
    console.log("Decryption successful!")

    // Generate public evaluation keys, also called ServerKey
    console.log("Generating compressed ServerKey...")
    let sks = Shortint.new_compressed_server_key(cks);

    // Can be serialized to send over the network to the machine doing the evaluation
    let serialized_sks = Shortint.serialize_compressed_server_key(sks);
    let deserialized_sks = Shortint.deserialize_compressed_server_key(serialized_sks);
    console.log("All done!")
}

shortint_example();

Then, you can run the example.js script using node as follows:

$ node example.js
Generating client keys...
Encrypting 3...
Decrypting ciphertext...
Decryption successful!
Generating compressed ServerKey...
All done!
$