TweetNaCl.js
============

Port of [TweetNaCl](http://tweetnacl.cr.yp.to) / [NaCl](http://nacl.cr.yp.to/)
to JavaScript for modern browsers and Node.js. Public domain.

[![Build Status](https://travis-ci.org/dchest/tweetnacl-js.svg?branch=master)
](https://travis-ci.org/dchest/tweetnacl-js)

[Demo](https://dchest.github.io/tweetnacl-js/)

**:warning: Beta version. The library is stable and API is frozen, however
it has not been independently reviewed. If you can help reviewing it, please
[contact me](mailto:dmitry@codingrobots.com).**

Documentation
=============

* [Overview](#overview)
* [Installation](#installation)
* [Usage](#usage)
  * [Public-key authenticated encryption (box)](#public-key-authenticated-encryption-box)
  * [Secret-key authenticated encryption (secretbox)](#secret-key-authenticated-encryption-secretbox)
  * [Scalar multiplication](#scalar-multiplication)
  * [Signatures](#signatures)
  * [Hashing](#hashing)
  * [Random bytes generation](#random-bytes-generation)
  * [Constant-time comparison](#constant-time-comparison)
  * [Utilities](#utilities)
* [Examples](#examples)
* [System requirements](#system-requirements)
* [Development and testing](#development-and-testing)
* [Contributors](#contributors)
* [Who uses it](#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.is via a package manager:

[Bower](http://bower.io):

    $ bower install tweetnacl

[NPM](https://www.npmjs.org/):

    $ npm install tweetnacl

or [download source code](https://github.com/dchest/tweetnacl-js/releases).


Usage
------

All API functions accept and return bytes as `Uint8Array`s.  If you need to
encode or decode strings, use functions from `nacl.util` namespace.

### 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](http://ed25519.cr.yp.to).

#### 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)

Note that browsers are required to throw `QuotaExceededError` exception if
requested `length` is more than 65536, so do not ask for more than 65536 bytes
in *one call* (multiple calls to get as many bytes as you like are okay:
browsers can generate infinite amount of random bytes without any bad
consequences).

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.


### Utilities

Encoding/decoding functions are provided for convenience. They are correct,
however their performance and wide compatibility with uncommon runtimes is not
something that is considered important compared to the simplicity and size of
implementation. You can use third-party libraries if you need to.

#### nacl.util.decodeUTF8(string)

Decodes string and returns `Uint8Array` of bytes.

#### nacl.util.encodeUTF8(array)

Encodes `Uint8Array` or `Array` of bytes into string.

#### nacl.util.decodeBase64(string)

Decodes Base-64 encoded string and returns `Uint8Array` of bytes.

#### nacl.util.encodeBase64(array)

Encodes `Uint8Array` or `Array` of bytes into string using Base-64 encoding.


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 (we test on 0.10 and later)


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 test

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 test

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

    $ npm run testall

To prepare tests for browsers:

    $ npm run browser

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

To run headless browser tests with `testling`:

    $ npm run testling

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

### 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`).


Contributors
------------

JavaScript port:

 * [Dmitry Chestnykh](http://github.com/dchest) (ported xsalsa20, poly1305, curve25519)
 * [Devi Mandiri](https://github.com/devi) (ported curve25519, ed25519, sha512)

Original authors of [NaCl](http://nacl.cr.yp.to), [TweetNaCl](http://tweetnacl.cr.yp.to)
and [Poly1305-donna](https://github.com/floodyberry/poly1305-donna)
(who are *not* responsible for any errors in this implementation):

  * [Daniel J. Bernstein](http://cr.yp.to/djb.html)
  * Wesley Janssen
  * [Tanja Lange](http://hyperelliptic.org/tanja)
  * [Peter Schwabe](http://www.cryptojedi.org/users/peter/)
  * [Matthew Dempsky](https://github.com/mdempsky)
  * [Andrew Moon](https://github.com/floodyberry)

Contributors have dedicated their work to the public domain.

This software is distributed without any warranty.


Who uses it
-----------

Some notable users of TweetNaCl.js:

* [miniLock](http://minilock.io/)
* [Stellar](https://www.stellar.org/)
