TweetNaCl.js

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

Demo: https://dchest.github.io/tweetnacl-js/

Documentation

• Overview
• Audits
• Security Considerations
• Installation
• Examples
• 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. (Used by default when importing NPM package.)

Audits

TweetNaCl.js has been audited by Cure53 in January-February 2017 (audit was sponsored by Deletype):

The overall outcome of this audit signals a particularly positive assessment for TweetNaCl-js, as the testing team was unable to find any security problems in the library.

Read full audit report

While the audit didn't find any bugs, there has been 1 bug discovered and fixed after the audit.

Security Considerations

It is important to note that TweetNaCl.js is a low-level library that doesn't provide complete security protocols. When designing protocols, you should carefully consider various properties of underlying primitives.

No secret key commitment

While XSalsa20-Poly1305, as used in nacl.secretbox and nacl.box, meets the standard notions of privacy and authenticity for a secret-key authenticated-encryption scheme using nonces, it is not key-committing, which means that it is possible to find a ciphertext which decrypts to valid plaintexts under two different keys. This may lead to vulnerabilities if encrypted messages are used in a context where key commitment is expected.

Signature malleability

While Ed25519 as originally defined and implemented in nacl.sign meets the standard notion of unforgeability for a public-key signature scheme under chosen-message attacks, it is malleable: given a signed message, it is possible, without knowing the secret key, to create a different signature for the same message that will verify under the same public key. This may lead to vulnerabilities if signatures are used in a context where malleability is not expected.

Hash length-extension attacks

The SHA-512 hash function, as implemented by nacl.hash, is not resistant to length-extension attacks.

Side-channel attacks

While TweetNaCl.js uses algorithmic constant-time operations, it is impossible to guarantee that they are physically constant time given JavaScript runtimes, JIT compilers, and other factors. It is also impossible to guarantee that secret data is physically removed from memory during cleanup due to copying garbage collectors and optimizing compilers.

Installation

You can install TweetNaCl.js via a package manager:

Yarn:

$ yarn add tweetnacl

NPM:

$ npm install tweetnacl

or download source code.

Examples

You can find usage examples in our wiki.

Usage

All API functions accept and return bytes as Uint8Arrays. 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 Uint8Arrays, so you can freely pass them to TweetNaCl.js functions as arguments. The returned objects are still Uint8Arrays, so if you need Buffers, you'll have to convert them manually; make sure to convert using copying: Buffer.from(array) (or new Buffer(array) in Node.js v4 or earlier), instead of sharing: Buffer.from(array.buffer) (or new Buffer(array.buffer) Node 4 or earlier), because some functions return subarrays of their buffers.

Public-key authenticated encryption (box)

Implements x25519-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)

Encrypts 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 null 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.

Constants

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)

Encrypts 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 null if authentication fails.

Constants

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 x25519.

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.

Constants

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.

Constants

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.

Constants

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 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, Xiaomi Redmi Note 3 smartphone with 1.8 GHz Qualcomm Snapdragon 650 64-bit CPU (ARM) in Chrome 52/Android, and MacBook Air 2020 with Apple M1 SOC (M1) in Chromium 102/macOS.

(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 500 and verify 300 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

• chloride - unified API for various NaCl modules
• forward-secrecy — Axolotl ratchet implementation
• nacl-stream - streaming encryption
• ristretto255-js — implementation of the ristretto255 group
• tweetnacl-auth-js — implementation of crypto_auth
• tweetnacl-js-sealed-box — fork that adds sealed boxes
• ed2curve — convert Ed25519 signing key pair to X25519 boxes key pair

Who uses it

Some notable users of TweetNaCl.js are listed on the associated wiki page.