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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 weighs 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
Bun
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:

Usage (as a module)

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

Example:

import _sodium from 'libsodium-wrappers';
await (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 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 only included in the sumo version.

The sumo version is slightly larger than the standard version, reserves more memory, 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.