scrypt-js

What is scrypt-js?

The scrypt-js npm package is a JavaScript implementation of the scrypt key derivation function. It is used primarily for securely hashing passwords and generating cryptographic keys.

What are scrypt-js's main functionalities?

Password Hashing

This feature allows you to hash a password using the scrypt key derivation function. The code sample demonstrates how to derive a key from a password and salt with specific parameters.

const scrypt = require('scrypt-js');
const password = Buffer.from('password');
const salt = Buffer.from('salt');
const N = 16384, r = 8, p = 1, dkLen = 32;
scrypt(password, salt, N, r, p, dkLen, (error, progress, key) => {
  if (error) {
    console.error(error);
  } else if (key) {
    console.log('Derived key:', key.toString('hex'));
  }
});

Key Derivation

This feature allows you to derive a cryptographic key from a secret and salt. The code sample shows how to generate a 64-byte key using the scrypt function.

const scrypt = require('scrypt-js');
const secret = Buffer.from('secret');
const salt = Buffer.from('salt');
const N = 16384, r = 8, p = 1, dkLen = 64;
scrypt(secret, salt, N, r, p, dkLen, (error, progress, key) => {
  if (error) {
    console.error(error);
  } else if (key) {
    console.log('Derived key:', key.toString('hex'));
  }
});

Other packages similar to scrypt-js

bcrypt

bcrypt is a popular library for hashing passwords. It is known for its simplicity and security. Unlike scrypt-js, bcrypt is specifically designed for password hashing and does not offer general key derivation functionality.

pbkdf2

pbkdf2 is another key derivation function available in the crypto module of Node.js. It is widely used for password hashing and key derivation. Compared to scrypt-js, pbkdf2 is generally faster but considered less secure against certain types of attacks.

argon2

argon2 is a modern key derivation function that won the Password Hashing Competition in 2015. It is designed to be highly secure and resistant to various types of attacks. Argon2 offers similar functionalities to scrypt-js but is considered more secure and efficient.

README

scrypt

The scrypt password-base key derivation function (pkbdf) is an algorithm for converting a human readable password into a fixed length of bytes, which can then be used as a key for symetric block ciphers, private keys. et cetera.

The scrypt algorithm is, by design, expensive to execute, which increases the amount of time an attacker requires in order to brute force guess a password, adjustable by several parameters which can be tuned:

• N - The general work factor; increasing this increases the difficulty of the overall derivation
• p - The memory cost; increasing this increases the memory required during derivation
• r - The parallelization factor; increasing the computation required during derivation

Features:

• Non-blocking - Gives other events in the event loop opportunities to run (asynchrorous)
• Cancellable - If the key is not longer required, the computation can be cancelled
• Progress Callback - Provides the current progress of key derivation as a percentage complete

Todo

These are all coming soon (as of 2016-03-11):

• Remove browser dependency on slow buffer
• Add test cases (from scrypt-async)
• Improve the demo page

Installing

node.js

You should likely not use this module for node.js as there are many faster alternatives, but if you so wish to:

npm install scrypt-js

browser

// coming soon
<script src="" type="text/javascript"></script>

API

Coming soon.

Encoding Notes

TL;DR - either only allow ASCII characters in passwords, or use
        String.prototype.normalize('NFKC') on any password

It is HIGHLY recommended that you do NOT pass strings into this (or any password-base key derivation function) library without careful consideration; you should convert your strings to a canonical format that you will use consistently across all platforms.

When encoding passowrds with UTF-8, it is important to realize that there may be multiple UTF-8 representations of a given string. Since the key generated by a password-base key derivation function is dependant on the specific bytes, this matters a great deal.

Composed vs. Decomposed

Certain UTF-8 code points can be combined with other characters to create composed characters. For example, the letter a with the umlaut diacritic mark (two dots over it) can be expressed two ways; as its composed form, U+00FC; or its decomposed form, which is the letter "u" followed by U+0308 (which basically means modify the previous character by adding an umlaut to it).

// In the following two cases, a "u" with an umlaut would be seen
> '\u00fc'
> 'u\u0308'


// In its composed form, it is 2 bytes long
> new Buffer('u\u0308'.normalize('NFKC'))
<Buffer c3 bc>
> new Buffer('\u00fc')
<Buffer c3 bc>

// Whereas the decomposed form is 3 bytes, the letter u followed by U+0308
> new Buffer('\u00fc'.normalize('NFKD'))
<Buffer 75 cc 88>
> new Buffer('u\u0308')
<Buffer 75 cc 88>

Compatibility equivalence mode

Certain strings are often displayed the same, even though they may have different semantic means. For example, UTF-8 provides a code point for the roman number for one, which appears as the letter I, in most fonts identically. Compatibility equivalence will fold these two cases into simply the capital letter I.

> '\u2160'
'I'
> 'I'
'I'
> 'u2160' === 'I'
false
> '\u2160'.normalize('NFKC') === 'I'
true

Normalizing

The normalize() method of a string can be used to convert a string to a specific form. Without going into too much detail, I generally recommend NFKC, however if you wish to dive deeper into this, a nice short summary can be found in Pythons unicodedata module's documentation.

For browsers without normalize() support, the npm unorm module can be used to polyfill strings.

Another example of encoding woes

One quick story I will share is a project which used the SHA256(encodeURI(password)) as a key, which (ignorig raindbow table attacks) had an unfortunate consequence of old web browsers replacing spaces with + while on new web browsers, replacing it with a %20, causing issues for anyone who used spaces in their password.

Suggestions

• While it may be inconvenient to many international users, one option is to restrict passwords to a safe subset of ASCII, for example: /^[A-Za-z0-9!@#$%^&*()]+$/.
• My personal recommendation is to normalize to the NFKC form, however, one could imagine setting their password to a Chinese phrase on one computer, and then one day using a computer that does not have Chinese input capabilites and therefore be unable to log in.

See: Unicode Equivalence

Based On

This code borrows HEAVILY from two other awesome scrpt libraries:

• scryptsy - This is the basis for this implementation of the base hashing algorithm
• scrypt-async - To remove the large dependency tree of pbkdf2 used in scryptsy, the custom (and highly performant) variant was used from this library

License

MIT license.

Donations

Obviously, it's all licensed under the MIT license, so use it as you wish; but if you'd like to buy me a coffee, I won't complain. =)

• Bitcoin - 1LsxZkCZpQXyiGsoAnAW9nRRfck3Nvv7QS
• Dogecoin - DF1VMTgyPsew619hwq5tT2RP8BNh2ZpzWA
• Testnet3 - muf7Vak4ZCVgtYZCnGStDXuoEdmZuo2nhA