scrypt

Scrypt For Node

Scrypt for Node/IO is a native node/io C++ wrapper for Colin Percival's scrypt cryptographic hash utility.

As should be the case with any security tool, this library should be scrutinized by anyone using it. If you find or suspect an issue with the code- please bring it to my attention and I'll spend some time trying to make sure that this tool is as secure as possible.

Node-Scrypt Version 5

Version 5 is a major new release that is not backward compatible with any previous version. Some highlights:

• C++ addon code rewritten:
  • Using Nan 2.x
  • Code has been greatly simplified
• ES6 Promise aware.
• API has changed:
  • Every output is a buffer.
  • Separated functions into async and sync versions.
  • Api name swap: What was kdf in previous versions is now hash (and vice versa).
  • Async functions will return a Promise if no callback function is present and Promises are available (else it will throw a SyntaxError).
• Using correct JavaScript Error object for all errors.

Migrating To Version 5

Version 5 is not backward compatible, but it should still be easy to migrate. Please read the api section to see what's changed. One big change that is worth noting is a name change: What used to be called hash has now been changed to kdf and conversely, what was kdf is now called hash.

Table Of Contents

• Scrypt
• Installation Instructions
• API - The module consists of four functions:
  • params - a translation function that produces scrypt parameters
  • kdf - a key derivation function designed for password hashing
  • verifyKdf - checks if a key matches a kdf
  • hash - the raw underlying scrypt hash function
• Example Usage
• FAQ
• Credits

Scrypt

Scrypt is an advanced crypto library used mainly for key derivation: More information can be found here:

• Tarsnap blurb about scrypt - Colin Percival (the author of scrypt) explains a bit about it.
• Academic paper explaining scrypt.
• Wikipedia Article on scrypt.

Installation Instructions

Pre-Requisistes

Windows

• Node-Gyp for Windows:
  • Installation instructions: node-gyp for windows
  • Look here for additional information/helpful hints.
• OppenSSL for Windows:
  • OpenSSL For Windows 32 bit
  • OpenSSL For Windows 64 bit

Linux/MacOS

Node-gyp is needed to build this module. It should be installed globally, that is, with the -g switch:

npm install -g node-gyp

Install From NPM

npm install scrypt

Install From Source

git clone https://github.com/barrysteyn/node-scrypt.git
cd node-scrypt
npm install
node-gyp configure build

Testing

To test, go to the folder where scrypt was installed, and type:

npm test

API

params

Translates human understandable parameters to scrypt's internal parameters.

scrypt.paramsSync
scrypt.params(maxtime, [maxmem, [max_memfrac]], [function(err, obj) {}])

• maxtime - [REQUIRED] - a decimal (double) representing the maximum amount of time in seconds scrypt will spend when computing the derived key.
• maxmem - [OPTIONAL] - an integer, specifying the maximum number of bytes of RAM used when computing the derived encryption key. If not present, will default to 0.
• maxmemfrac - [OPTIONAL only if maxmem is present] - a double value between 0.0 and 1.0, representing the fraction (normalized percentage value) of the available RAM used when computing the derived key. If not present, will default to 0.5.
• callback_function - [OPTIONAL] - not applicable to synchronous function. If present in async function, then it will be treated as a normal async callback. If not present, a Promise will be returned if ES6 promises are available. If not present and ES6 promises are not present, a SyntaxError will be thrown.

kdf

Note: In previous versions, this was called hash.

Produces a key derivation function that uses the scrypt hash function. This should be used for hashing and checking passwords as it incorporates salt as well as HMAC into its format. It is based on a design by Colin Percival, the author of scrypt. The format can be seen here.

scrypt.kdfSync
scrypt.kdf(key, paramsObject, [function(err, obj){}])

• key - [REQUIRED] - a string (or buffer) representing the key (password) that is to be hashed.
• paramsObject - [REQUIRED] - parameters to control scrypt hashing (see params above).
• callback_function - [OPTIONAL] - not applicable to synchronous function. If present in async function, then it will be treated as a normal async callback. If not present, a Promise will be returned if ES6 promises are available. If not present and ES6 promises are not present, a SyntaxError will be thrown.

verifyKdf

Checks if a key (password) matches a kdf.

scrypt.verifyKdfSync
scrypt.verifyKdf(kdf, key, [function(err, result){}])

• kdf [REQUIRED] - see kdf above.
• key - [REQUIRED] - a string (or buffer) representing the key (password) that is to be checked.
• callback_function - [OPTIONAL] - not applicable to synchronous function. If present in async function, then it will be treated as a normal async callback. If not present, a Promise will be returned if ES6 promises are available. If not present and ES6 promises are not present, a SyntaxError will be thrown.

hash

Note: In previous versions, this was called kdf.

This is the raw scrypt hash function.

scrypt.hashSync
scrypt.hash(key, paramsObject, output_length, function(err, obj){})

• key - [REQUIRED] - a string (or buffer) representing the key (password) that is to be checked.
• paramsObject - [REQUIRED] - parameters to control scrypt hashing (see params above).
• output_length - [REQUIRED] - the length of the resulting hashed output.
• callback_function - [OPTIONAL] - not applicable to synchronous function. If present in async function, then it will be treated as a normal async callback. If not present, a Promise will be returned if ES6 promises are available. If not present and ES6 promises are not present, a SyntaxError will be thrown.

Example Usage

params

var scrypt = require("scrypt");

//Synchronous
try {
  //Uses 0.1 for maxtime, and default values maxmem and maxmemfrac
  var scryptParameters = scrypt.paramsSync(0.1);
  console.log(scryptParameters);
} catch(err) {
  //handle error
}

//Asynchronous with callback
scrypt.params(0.1, function(err, scryptParameters) {
  console.log(scryptParameters);
});

//Asynchronous with promise
scrypt.params(0.1).then(function(result){
  console.log(result);
}, function(err) {
  console.log(err);
});

kdf

var scrypt = require("scrypt");
var scryptParameters = scrypt.paramsSync(0.1);
var key = new Buffer("this is a key"); //could also be a string

//Synchronous example that will output in hexidecimal encoding
var kdfResult = scrypt.kdfSync(key, scryptParameters); //should be wrapped in try catch, but leaving it out for brevity
console.log("Synchronous result: "+kdfResult.toString("hex"));

//Asynchronous example that expects key to be ascii encoded
scrypt.kdf("ascii encoded key", {N: 1, r:1, p:1}, function(err, result){
  //Note how scrypt parameters was passed as a JSON object
  console.log("Asynchronous result: "+result.toString("base64"));
});

//Asynchronous with promise
scrypt.kdf("ascii encoded key", {N: 1, r:1, p:1}).then(function(result){
  console.log("Asynchronous result: "+result.toString("base64"));
}, function(err){
});

verifyKdf

var scrypt = require("scrypt");
var scryptParameters = scrypt.paramsSync(0.1);
var kdfResult = scrypt.kdfSync("password", scryptParameters);

//Synchronous
scrypt.verifyKdfSync(kdfResult, "password"); // returns true
scrypt.verifyKdfSync(kdfResult, "incorrect password"); // returns false

//Asynchronous
scrypt.verifyKdf(kdfResult, new Buffer("password"), function(err, result) {
  //result will be true
});

//Asynchronous with promise
scrypt.verifyKdf(kdfResult, "incorrect password").then(function(result) {
  //result will be false
}, function(err) {
});

hash

The scrypt paper lists four test vectors to test implementation. This example will show how to produce these test vectors from within this module.

Test Vector 1

var scrypt = require("scrypt");
var key = new Buffer("");

//Synchronous
var result = scrypt.hashSync(key,{"N":16,"r":1,"p":1},64,"");
console.log(result.toString("hex"));

//Asynchronous
scrypt.hash(key, {"N":16,"r":1,"p":1},64,"", function(err, res) {
  console.log(result.toString("hex"));
});

//Asynchronous with promise
scrypt.hash(key, {"N":16,"r":1,"p":1},64,"").then(function(result) {
  console.log(result.toString("hex"));
}, function(err){});

Test Vector 2

var scrypt = require("scrypt");
var salt = new Buffer("NaCl");

//Synchronous
var result = scrypt.hashSync("password", {"N":1024,"r":8,"p":16}, 64, salt);
console.log(result.toString("hex"));

scrypt.hash("password", {"N":1024,"r":8,"p":16},64,salt, function(err, result) {
  console.log(result.toString("hex"));
});

Test Vector 3

var scrypt = require("scrypt");
var key = new Buffer("pleaseletmein");
var salt = new Buffer("SodiumChloride");

//Synchronous
var result = scrypt.hashSync(key,{"N":16384,"r":8,"p":1},64,salt);
console.log(result.toString("hex"));

//Asynchronous
scrypt.hash(key, {"N":16384,"r":8,"p":1}, 64, salt, function(err, result) {
  console.log(result.toString("hex"));
});

Test Vector 4

Note: This test vector is very taxing in terms of resources.

var scrypt = require("scrypt");

//Synchronous
var result = scrypt.hashSync("pleaseletmein",{"N":1048576,"r":8,"p":1},64,"SodiumChloride");
console.log(result.toString("hex"));

//Asynchronous
scrypt.hash("pleaseletmein", {"N":1048576,"r":8,"p":1},64,"SodiumChloride", function(err, result) {
  console.log(result.toString("hex"));
});

FAQ

General

What Platforms Are Supported?

This module supports most posix platforms, as well as Microsoft Windows. It has been tested on the following platforms: Linux, MAC OS, SmartOS (so its ready for Joyent Cloud) and Microsoft Windows. It also works on FreeBSD, OpenBSD, SunOS etc.

Scrypt

Why Use Scrypt?

It is probably the most advanced key derivation function available. This is is quote taken from a comment in hacker news:

Passwords hashed with scrypt with sufficiently-high strength values (there are 3 tweakable input numbers) are fundamentally impervious to being cracked. I use the word "fundamental" in the literal sense, here; even if you had the resources of a large country, you would not be able to design any hardware (whether it be GPU hardware, custom-designed hardware, or otherwise) which could crack these hashes. Ever. (For sufficiently-small definitions of "ever". At the very least "within your lifetime"; probably far longer.)

What Are The Pros And Cons For Using Scrypt?

Pros

• The scrypt algorithm has been published by IETF as an Internet Draft and is thus on track to becoming a standard. See here for the draft.
• It is being actively used in production at Tarsnap.
• It is much more secure than bcrypt.
• It is designed to be future proof against attacks with future (and more advanced) hardware.
• It is designed to defend against large scale custom hardware attacks.
• It is production ready.
• There is a scrypt library for most major scripting languages (Python, Ruby etc). Now this module provides the library for NodeJS :)

I will end this section with a quote from Colin Percival (author of scrypt):

We estimate that on modern (2009) hardware, if 5 seconds are spent computing a derived key, the cost of a hardware brute-force attack against scrypt is roughly 4000 times greater than the cost of a similar attack against bcrypt (to find the same password), and 20000 times greater than a similar attack against PBKDF2.

Cons

There is just one con I can think of: It is a relatively new library (only been around since 2009). Cryptographers don't really like new libraries for production deployment as it has not been battle tested. That being said, it is being actively used in Tarsnap (as mentioned above) and the author is very active.

Using Scrypt With Passwords

What Are The Essential Properties For Storing Passwords?

Storing passwords requires three essential properties

• The password must not be stored in plaintext.
• The password hash must be salted. (Making a rainbow table attack very difficult to pull off).
• The salted hash function must not be fast. (If someone does get hold of the salted hashes, their only option will be brute force which will be very slow).

As an example of how storing passwords can be done badly, take LinkedIn. In 2012, they came under fire for using unsalted hashes to store their passwords. As most commentators at the time were focusing no salt being present, the big picture was missed. In fact, their biggest problem was that they used sha1, a very fast hash function.

If random salts are used, why do all resulting KDF's start with c2NyeXB0?

The kdf has a specific format: The word "scrypt" is added as a prefix. The reason for this is because I am sticking to Colin Percival's (the creator of scrypt) reference implementation, whereby he prefixes scrypt in this way. The base64 encoding of the ascii "scrypt" is c2NyeXB0. The scrypt parameters are then appended. Users of scrypt normally do not change this information once it is settled upon (hence this will also look the be identical).

To illustrate with an example, I have hashed two password: password1 and password2. Their Base64 outputs are as follows:

password1
c2NyeXB0AAwAAAAIAAAAAcQ0zwp7QNLklxCn14vB75AYWDIrrT9I/7F9+lVGBfKN/1TH2hs
/HboSy1ptzN0YzHJhC7PZIEPQzf2nuoaqVZg8VkKEJlo8/QaH7qjU2VwB

password2
c2NyeXB0AAwAAAAIAAAAAZ/+bp8gWcTZgEC7YQZeLLyxFeKRRdDkwbaGeFC0NkdUr/YFAWY
/UwdOH4i/PxW48fXeXBDOTvGWtS3lLUgzNM0PlJbXhMOGd2bke0PvTSnW

As one can see from the above example, both hashes start off by looking similar (they both start with c2NyeXB0AAwAAAAIAAAAA - as explained above), but after this, things change very rapidly. In fact, I hashed the password password1 again:

password1
c2NyeXB0AAwAAAAIAAAAATpP+fdQAryDiRmCmcoOrZa2mZ049KdbA/ofTTrATQQ+m
0L/gR811d0WQyip6p2skXVEMz2+8U+xGryFu2p0yzfCxYLUrAaIzaZELkN2M6k0

Compare this hash to the one above. Even though they start off looking similar, their outputs are vastly different (even though it is the same password being hashed). This is because of the random salt that has been added, ensuring that no two hashes will ever be identical, even if the password that is being hashed is the same.

For those that are curious or paranoid, please look at how the kdf is both produced and verified (you are going to need some knowledge of the C language for this).

Roadmap

Incorportate version 1.2.0

Colin Percival has released a new version of scrypt, the first new version in five years. While it is not more secure than the current version, it does allow things to be done with more ease (like support for other platforms).

Better Windows support

Credits

The scrypt library is Colin Percival's scrypt project.

Syed Beparey was instrumental in getting the Windows build working, with most of the Windows build based off the work done by Dinesh Shanbhag.

Changelog

[5.2.0] - 2015-10-06

Fixed

• Allow building on MS 2015