Multi-Factor Key Derivation Function

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The Multi-Factor Key Derivation Function (MFKDF) is a function that takes multiple inputs and outputs a string of bytes that can be used as a cryptographic key. It serves the same purpose as a pasword-based key derivation function (PBKDF), but is stronger than password-based key derivation due to its support for multiple authentication factors. MFKDF also supports account recovery via K-of-N (secret-sharing style) key derivation.

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Installation

In a browser:

Get the latest tag with SRI from jsDelivr (recommended), or include the latest version automatically like so:

<script src="https://cdn.jsdelivr.net/gh/multifactor/mfkdf/mfkdf.min.js"></script>

Using npm:

npm install mfkdf

In Node.js:

const mfkdf = require('mfkdf');

Usage

n-of-n MFKDF

MFKDF allows a key to be derived from several factors of input (eg. multiple passwords).

// setup MFKDF where 3/3 passwords are required
const { key, config } = await mfkdf.setup({
	password1: await mfkdf.factors.password('password1'),
	password2: await mfkdf.factors.password('password2'),
	password3: await mfkdf.factors.password('password3')
}, 3)

// derive key using 3/3 passwords
const key2 = await mfkdf.derive({
	password1: await mfkdf.factors.password('password1'),
	password2: await mfkdf.factors.password('password2'),
	password3: await mfkdf.factors.password('password3')
}, config)
console.log(key.toString('hex') === key2.toString('hex')) // true

// incorrect password will yield incorrect key
const key2 = await mfkdf.derive({
	password1: await mfkdf.factors.password('password1'),
	password2: await mfkdf.factors.password('password2'),
	password3: await mfkdf.factors.password('password4')
}, config)
console.log(key.toString('hex') === key2.toString('hex')) // false

k-of-n MFKDF

MFKDF can be configured to use k-of-n secret sharing style derivation (eg. any 2 of 3 passwords are sufficient).

// setup MFKDF where 2/3 passwords are required
const { key, config } = await mfkdf.setup({
	password1: await mfkdf.factors.password('password1'),
	password2: await mfkdf.factors.password('password2'),
	password3: await mfkdf.factors.password('password3')
}, 2)

// derive key using 2/3 passwords
const key2 = await mfkdf.derive({
	password1: await mfkdf.factors.password('password1'),
	password2: await mfkdf.factors.password('password2')
}, config)
console.log(key.toString('hex') === key2.toString('hex')) // true

// incorrect password will yield incorrect key
const key2 = await mfkdf.derive({
	password1: await mfkdf.factors.password('password1'),
	password2: await mfkdf.factors.password('password4')
}, config)
console.log(key.toString('hex') === key2.toString('hex')) // false

KDF

This library also supports a number of traditional password-based KDFs (pbkdf2, bcrypt, scrypt, argon2i, argon2d, and argon2id) which can be consumed directly like so:

// derive 256b key using pbkdf2-sha256 with 100,000 rounds
const mfkdf = require('mfkdf');
const key = await mfkdf.kdf('password', 'salt', {
  kdf: 'pbkdf2',
  size: 32,
  pbkdf2rounds: 100000,
  pbkdf2digest: 'sha256'
});

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