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TweetNaCl.js

Port of TweetNaCl / NaCl to JavaScript for modern browsers and Node.js. Public domain.

Demo: https://tweetnacl.js.org

**:warning: The library is stable and API is frozen, however it has not been independently reviewed. If you can help reviewing it, please contact me.**

# Documentation

- Overview
- Installation
- Usage
  - Public-key authenticated encryption (box)
  - Secret-key authenticated encryption (secretbox)
  - Scalar multiplication
  - Signatures
  - Hashing
  - Random bytes generation
  - Constant-time comparison
- System requirements
- Development and testing
- Benchmarks
- Contributors
- Who uses it

## Overview

The primary goal of this project is to produce a translation of TweetNaCl to JavaScript which is as close as possible to the original C implementation, plus a thin layer of idiomatic high-level API on top of it.

There are two versions, you can use either of them:

- `nacl.js` is the port of TweetNaCl with minimum differences from the original + high-level API.
- `nacl-fast.js` is like `nacl.js`, but with some functions replaced with faster versions.

## Installation

You can install TweetNaCl.js via a package manager:

Bower:

    $ bower install tweetnacl

NPM:

    $ npm install tweetnacl

or download source code.

## Usage

All API functions accept and return bytes as `Uint8Array`s. If you need to encode or decode strings, use functions from https://github.com/dchest/tweetnacl-util-js or one of the more robust codec packages.

In Node.js v4 and later `Buffer` objects are backed by `Uint8Array`s, so you can freely pass them to TweetNaCl.js functions as arguments. The returned objects are still `Uint8Array`s, so if you need `Buffer`s, you'll have to convert them manually; make sure to convert using copying: `new Buffer(array)`, instead of sharing: `new Buffer(array.buffer)`, because some functions return subarrays of their buffers.

### Public-key authenticated encryption (box)

Implements curve25519-xsalsa20-poly1305.

#### nacl.box.keyPair()

Generates a new random key pair for box and returns it as an object with `publicKey` and `secretKey` members:

    {
       publicKey: ...,  // Uint8Array with 32-byte public key
       secretKey: ...   // Uint8Array with 32-byte secret key
    }

#### nacl.box.keyPair.fromSecretKey(secretKey)

Returns a key pair for box with public key corresponding to the given secret key.

#### nacl.box(message, nonce, theirPublicKey, mySecretKey)

Encrypt and authenticates message using peer's public key, our secret key, and the given nonce, which must be unique for each distinct message for a key pair.

Returns an encrypted and authenticated message, which is `nacl.box.overheadLength` longer than the original message.

#### nacl.box.open(box, nonce, theirPublicKey, mySecretKey)

Authenticates and decrypts the given box with peer's public key, our secret key, and the given nonce.

Returns the original message, or `false` if authentication fails.

#### nacl.box.before(theirPublicKey, mySecretKey)

Returns a precomputed shared key which can be used in `nacl.box.after` and `nacl.box.open.after`.

#### nacl.box.after(message, nonce, sharedKey)

Same as `nacl.box`, but uses a shared key precomputed with `nacl.box.before`.

#### nacl.box.open.after(box, nonce, sharedKey)

Same as `nacl.box.open`, but uses a shared key precomputed with `nacl.box.before`.

#### nacl.box.publicKeyLength = 32

Length of public key in bytes.

#### nacl.box.secretKeyLength = 32

Length of secret key in bytes.

#### nacl.box.sharedKeyLength = 32

Length of precomputed shared key in bytes.

#### nacl.box.nonceLength = 24

Length of nonce in bytes.

#### nacl.box.overheadLength = 16

Length of overhead added to box compared to original message.

### Secret-key authenticated encryption (secretbox)

Implements xsalsa20-poly1305.

#### nacl.secretbox(message, nonce, key)

Encrypt and authenticates message using the key and the nonce. The nonce must be unique for each distinct message for this key.

Returns an encrypted and authenticated message, which is `nacl.secretbox.overheadLength` longer than the original message.

#### nacl.secretbox.open(box, nonce, key)

Authenticates and decrypts the given secret box using the key and the nonce.

Returns the original message, or `false` if authentication fails.

#### nacl.secretbox.keyLength = 32

Length of key in bytes.

#### nacl.secretbox.nonceLength = 24

Length of nonce in bytes.

#### nacl.secretbox.overheadLength = 16

Length of overhead added to secret box compared to original message.

### Scalar multiplication

Implements curve25519.

#### nacl.scalarMult(n, p)

Multiplies an integer `n` by a group element `p` and returns the resulting group element.

#### nacl.scalarMult.base(n)

Multiplies an integer `n` by a standard group element and returns the resulting group element.

#### nacl.scalarMult.scalarLength = 32

Length of scalar in bytes.

#### nacl.scalarMult.groupElementLength = 32

Length of group element in bytes.

### Signatures

Implements ed25519.

#### nacl.sign.keyPair()

Generates new random key pair for signing and returns it as an object with `publicKey` and `secretKey` members:

    {
       publicKey: ...,  // Uint8Array with 32-byte public key
       secretKey: ...   // Uint8Array with 64-byte secret key
    }

#### nacl.sign.keyPair.fromSecretKey(secretKey)

Returns a signing key pair with public key corresponding to the given 64-byte secret key. The secret key must have been generated by `nacl.sign.keyPair` or `nacl.sign.keyPair.fromSeed`.

#### nacl.sign.keyPair.fromSeed(seed)

Returns a new signing key pair generated deterministically from a 32-byte seed. The seed must contain enough entropy to be secure. This method is not recommended for general use: instead, use `nacl.sign.keyPair` to generate a new key pair from a random seed.

#### nacl.sign(message, secretKey)

Signs the message using the secret key and returns a signed message.

#### nacl.sign.open(signedMessage, publicKey)

Verifies the signed message and returns the message without signature.

Returns `null` if verification failed.

#### nacl.sign.detached(message, secretKey)

Signs the message using the secret key and returns a signature.

#### nacl.sign.detached.verify(message, signature, publicKey)

Verifies the signature for the message and returns `true` if verification succeeded or `false` if it failed.

#### nacl.sign.publicKeyLength = 32

Length of signing public key in bytes.

#### nacl.sign.secretKeyLength = 64

Length of signing secret key in bytes.

#### nacl.sign.seedLength = 32

Length of seed for `nacl.sign.keyPair.fromSeed` in bytes.

#### nacl.sign.signatureLength = 64

Length of signature in bytes.

### Hashing

Implements SHA-512.

#### nacl.hash(message)

Returns SHA-512 hash of the message.

#### nacl.hash.hashLength = 64

Length of hash in bytes.

### Random bytes generation

#### nacl.randomBytes(length)

Returns a `Uint8Array` of the given length containing random bytes of cryptographic quality.

Implementation note

TweetNaCl.js uses the following methods to generate random bytes, depending on the platform it runs on:

- `window.crypto.getRandomValues` (WebCrypto standard)
- `window.msCrypto.getRandomValues` (Internet Explorer 11)
- `crypto.randomBytes` (Node.js)

If the platform doesn't provide a suitable PRNG, the following functions, which require random numbers, will throw exception:

- `nacl.randomBytes`
- `nacl.box.keyPair`
- `nacl.sign.keyPair`

Other functions are deterministic and will continue working.

If a platform you are targeting doesn't implement secure random number generator, but you somehow have a cryptographically-strong source of entropy (not `Math.random`!), and you know what you are doing, you can plug it into TweetNaCl.js like this:

    nacl.setPRNG(function(x, n) {
      // ... copy n random bytes into x ...
    });

Note that `nacl.setPRNG` completely replaces internal random byte generator with the one provided.

### Constant-time comparison

#### nacl.verify(x, y)

Compares `x` and `y` in constant time and returns `true` if their lengths are non-zero and equal, and their contents are equal.

Returns `false` if either of the arguments has zero length, or arguments have different lengths, or their contents differ.

## System requirements

TweetNaCl.js supports modern browsers that have a cryptographically secure pseudorandom number generator and typed arrays, including the latest versions of:

- Chrome
- Firefox
- Safari (Mac, iOS)
- Internet Explorer 11

Other systems:

- Node.js

## Development and testing

Install NPM modules needed for development:

    $ npm install

To build minified versions:

    $ npm run build

Tests use minified version, so make sure to rebuild it every time you change `nacl.js` or `nacl-fast.js`.

### Testing

To run tests in Node.js:

    $ npm run test-node

By default all tests described here work on `nacl.min.js`. To test other versions, set environment variable `NACL_SRC` to the file name you want to test. For example, the following command will test fast minified version:

    $ NACL_SRC=nacl-fast.min.js npm run test-node

To run full suite of tests in Node.js, including comparing outputs of JavaScript port to outputs of the original C version:

    $ npm run test-node-all

To prepare tests for browsers:

    $ npm run build-test-browser

and then open `test/browser/test.html` (or `test/browser/test-fast.html`) to run them.

To run headless browser tests with `tape-run` (powered by Electron):

    $ npm run test-browser

(If you get `Error: spawn ENOENT`, install xvfb: `sudo apt-get install xvfb`.)

To run tests in both Node and Electron:

    $ npm test

### Benchmarking

To run benchmarks in Node.js:

    $ npm run bench
    $ NACL_SRC=nacl-fast.min.js npm run bench

To run benchmarks in a browser, open `test/benchmark/bench.html` (or `test/benchmark/bench-fast.html`).

## Benchmarks

For reference, here are benchmarks from MacBook Pro (Retina, 13-inch, Mid 2014) laptop with 2.6 GHz Intel Core i5 CPU (Intel) in Chrome 53/OS X and Xiaomi Redmi Note 3 smartphone with 1.8 GHz Qualcomm Snapdragon 650 64-bit CPU (ARM) in Chrome 52/Android:

| nacl.js Intel | nacl-fast.js Intel | nacl.js ARM | nacl-fast.js ARM
--- | --- | --- | --- | ---
salsa20 | 1.3 MB/s | 128 MB/s | 0.4 MB/s | 43 MB/s
poly1305 | 13 MB/s | 171 MB/s | 4 MB/s | 52 MB/s
hash | 4 MB/s | 34 MB/s | 0.9 MB/s | 12 MB/s
secretbox 1K | 1113 op/s | 57583 op/s | 334 op/s | 14227 op/s
box 1K | 145 op/s | 718 op/s | 37 op/s | 368 op/s
scalarMult | 171 op/s | 733 op/s | 56 op/s | 380 op/s
sign | 77 op/s | 200 op/s | 20 op/s | 61 op/s
sign.open | 39 op/s | 102 op/s | 11 op/s | 31 op/s

(You can run benchmarks on your devices by clicking on the links at the bottom of the home page).

In short, with nacl-fast.js and 1024-byte messages you can expect to encrypt and authenticate more than 57000 messages per second on a typical laptop or more than 14000 messages per second on a $170 smartphone, sign about 200 and verify 100 messages per second on a laptop or 60 and 30 messages per second on a smartphone, per CPU core (with Web Workers you can do these operations in parallel), which is good enough for most applications.

## Contributors

See AUTHORS.md file.

## Third-party libraries based on TweetNaCl.js

- forward-secrecy — Axolotl ratchet implementation
- nacl-stream - streaming encryption
- tweetnacl-auth-js — implementation of `crypto_auth`
- chloride - unified API for various NaCl modules

## Who uses it

Some notable users of TweetNaCl.js:

- miniLock
- Stellar