libsodium.js

Overview

The sodium crypto library
compiled to WebAssembly and pure JavaScript using
Emscripten, with
automatically generated wrappers to make it easy to use in web
applications.

The complete library weights 188 KB (minified, gzipped, includes pure JS +
WebAssembly versions) and can run in a web browser as well as server-side.

Compatibility

Supported browsers/JS engines:

• Chrome >= 16
• Edge >= 0.11
• Firefox >= 21
• Mobile Safari on iOS >= 8.0 (older versions produce incorrect results)
• NodeJS
• Opera >= 15
• Safari >= 6 (older versions produce incorrect results)

This is comparable to the WebCrypto API, which is compatible with a
similar number of browsers.

Signatures and other Edwards25519-based operations are compatible with
WasmCrypto.

Installation

The dist
directory contains pre-built scripts. Copy the files from one of its
subdirectories to your application:

• browsers
  includes a single-file script that can be included in web pages.
  It contains code for commonly used functions.
• browsers-sumo
  is a superset of the previous script, that contains all functions,
  including rarely used ones and undocumented ones.
• modules
  includes commonly used functions, and is designed to be loaded as a module.
  libsodium-wrappers is the module your application should load, which
  will in turn automatically load libsodium as a dependency.
• modules-sumo
  contains sumo variants of the previous modules.

The modules are also available on npm:

• libsodium-wrappers
• libsodium-wrappers-sumo

If you prefer Bower:

bower install libsodium.js

Usage (as a module)

Load the sodium-wrappers module. The returned object contains a .ready
property: a promise that must be resolve before the sodium functions
can be used.

Example:

const _sodium = require('libsodium-wrappers');
(async() => {
  await _sodium.ready;
  const sodium = _sodium;

  let key = sodium.crypto_secretstream_xchacha20poly1305_keygen();

  let res = sodium.crypto_secretstream_xchacha20poly1305_init_push(key);
  let [state_out, header] = [res.state, res.header];
  let c1 = sodium.crypto_secretstream_xchacha20poly1305_push(state_out,
    sodium.from_string('message 1'), null,
    sodium.crypto_secretstream_xchacha20poly1305_TAG_MESSAGE);
  let c2 = sodium.crypto_secretstream_xchacha20poly1305_push(state_out,
    sodium.from_string('message 2'), null,
    sodium.crypto_secretstream_xchacha20poly1305_TAG_FINAL);

  let state_in = sodium.crypto_secretstream_xchacha20poly1305_init_pull(header, key);
  let r1 = sodium.crypto_secretstream_xchacha20poly1305_pull(state_in, c1);
  let [m1, tag1] = [sodium.to_string(r1.message), r1.tag];
  let r2 = sodium.crypto_secretstream_xchacha20poly1305_pull(state_in, c2);
  let [m2, tag2] = [sodium.to_string(r2.message), r2.tag];

  console.log(m1);
  console.log(m2);
})();

Usage (in a web browser, via a callback)

The sodium.js file includes both the core libsodium functions, as
well as the higher-level JavaScript wrappers. It can be loaded
asynchronusly.

A sodium object should be defined in the global namespace, with the
following property:

• onload: the function to call after the wrapper is initialized.

Example:

<script>
    window.sodium = {
        onload: function (sodium) {
            let h = sodium.crypto_generichash(64, sodium.from_string('test'));
            console.log(sodium.to_hex(h));
        }
    };
</script>
<script src="sodium.js" async></script>

Additional helpers

• from_base64(), to_base64() with an optional second parameter
  whose value is one of: base64_variants.ORIGINAL, base64_variants.ORIGINAL_NO_PADDING,
  base64_variants.URLSAFE or s.base64_variants.URLSAFE_NO_PADDING. Default is base64_variants.URLSAFE_NO_PADDING.
• from_hex(), to_hex()
• from_string(), to_string()
• pad(<buffer>, <block size>), unpad(<buffer>, <block size>)
• memcmp() (constant-time check for equality, returns true or false)
• compare() (constant-time comparison. Values must have the same
  size. Returns -1, 0 or 1)
• memzero() (applies to Uint8Array objects)
• increment() (increments an arbitrary-long number stored as a
  little-endian Uint8Array - typically to increment nonces)
• add() (adds two arbitrary-long numbers stored as little-endian
  Uint8Array vectors)
• is_zero() (constant-time, checks Uint8Array objects for all zeros)

API

The API exposed by the wrappers is identical to the one of the C
library, except that buffer lengths never need to be explicitly given.

Binary input buffers should be Uint8Array objects. However, if a string
is given instead, the wrappers will automatically convert the string
to an array containing a UTF-8 representation of the string.

Example:

var key = sodium.randombytes_buf(sodium.crypto_shorthash_KEYBYTES),
    hash1 = sodium.crypto_shorthash(new Uint8Array([1, 2, 3, 4]), key),
    hash2 = sodium.crypto_shorthash('test', key);

If the output is a unique binary buffer, it is returned as a
Uint8Array object.

Example (secretbox):

let key = sodium.from_hex('724b092810ec86d7e35c9d067702b31ef90bc43a7b598626749914d6a3e033ed');

function encrypt_and_prepend_nonce(message) {
    let nonce = sodium.randombytes_buf(sodium.crypto_secretbox_NONCEBYTES);
    return nonce.concat(sodium.crypto_secretbox_easy(message, nonce, key));
}

function decrypt_after_extracting_nonce(nonce_and_ciphertext) {
    if (nonce_and_ciphertext.length < sodium.crypto_secretbox_NONCEBYTES + sodium.crypto_secretbox_MACBYTES) {
        throw "Short message";
    }
    let nonce = nonce_and_ciphertext.slice(0, sodium.crypto_secretbox_NONCEBYTES),
        ciphertext = nonce_and_ciphertext.slice(sodium.crypto_secretbox_NONCEBYTES);
    return sodium.crypto_secretbox_open_easy(ciphertext, nonce, key);
}

In addition, the from_hex, to_hex, from_string, and to_string
functions are available to explicitly convert hexadecimal, and
arbitrary string representations from/to Uint8Array objects.

Functions returning more than one output buffer are returning them as
an object. For example, the sodium.crypto_box_keypair() function
returns the following object:

{ keyType: 'curve25519', privateKey: (Uint8Array), publicKey: (Uint8Array) }

Standard vs Sumo version

The standard version (in the dist/browsers and dist/modules
directories) contains the high-level functions, and is the recommended
one for most projects.

Alternatively, the "sumo" version, available in the
dist/browsers-sumo and dist/modules-sumo directories contains all
the symbols from the original library. This includes undocumented,
untested, deprecated, low-level and easy to misuse functions.

The crypto_pwhash_* function set is included in both versions.

The sumo version is slightly larger than the standard version, and
should be used only if you really need the extra symbols it provides.

Compilation

If you want to compile the files yourself, the following dependencies
need to be installed on your system:

• Emscripten
• binaryen
• git
• NodeJS
• make

Running make will install the dev dependencies, clone libsodium,
build it, test it, build the wrapper, and create the modules and
minified distribution files.

Authors

Built by Ahmad Ben Mrad, Frank Denis and Ryan Lester.

License

This wrapper is distributed under the
ISC License.