keyxpanse

keyxpanse is a JavaScript tool to generate, import and export Expanse keys. This provides a simple way to use the same account locally and in web wallets. It can be used for verifiable cold storage wallets.

keyxpanse uses the same key derivation functions (PBKDF2-SHA256 or scrypt), symmetric ciphers (AES-128-CTR or AES-128-CBC), and message authentication codes as gexp. You can export your generated key to file, copy it to your data directory's keystore, and immediately start using it in your local Expanse client.

Note: starting in version 0.5.0, keyxpanse's encrypt and decrypt functions both return Buffers instead of strings. This is a breaking change for anyone using these functions directly!

Installation

npm install keyxpanse

Usage

To use keyxpanse in Node.js, just require it:

var keyxpanse = require("keyxpanse");

A minified, browserified file dist/keyxpanse.min.js is included for use in the browser. Including this file simply attaches the keyxpanse object to window:

<script src="dist/keyxpanse.min.js" type="text/javascript"></script>

Key creation

Generate a new random private key (256 bit), as well as the salt (256 bit) used by the key derivation function, and the initialization vector (128 bit) used to AES-128-CTR encrypt the key. create is asynchronous if it is passed a callback function, and synchronous otherwise.

// optional private key and initialization vector sizes in bytes
// (if params is not passed to create, keyxpanse.constants is used by default)
var params = { keyBytes: 32, ivBytes: 16 };

// synchronous
var dk = keyxpanse.create(params);
// dk:
{
    privateKey: <Buffer ...>,
    iv: <Buffer ...>,
    salt: <Buffer ...>
}

// asynchronous
keyxpanse.create(params, function (dk) {
    // do stuff!
});

Key export

You will need to specify a password and (optionally) a key derivation function. If unspecified, PBKDF2-SHA256 will be used to derive the AES secret key.

var password = "wheethereum";
var kdf = "pbkdf2"; // or "scrypt" to use the scrypt kdf

The dump function is used to export key info to keystore "secret-storage" format. If a callback function is supplied as the sixth parameter to dump, it will run asynchronously:

// Note: if options is unspecified, the values in keyxpanse.constants are used.
var options = {
  kdf: "pbkdf2",
  cipher: "aes-128-ctr",
  kdfparams: {
    c: 262144,
    dklen: 32,
    prf: "hmac-sha256"
  }
};

// synchronous
var keyObject = keyxpanse.dump(password, dk.privateKey, dk.salt, dk.iv, options);
// keyObject:
{
  address: "008aeeda4d805471df9b2a5b0f38a0c3bcba786b",
  Crypto: {
    cipher: "aes-128-ctr",
    ciphertext: "5318b4d5bcd28de64ee5559e671353e16f075ecae9f99c7a79a38af5f869aa46",
    cipherparams: {
      iv: "6087dab2f9fdbbfaddc31a909735c1e6"
    },
    mac: "517ead924a9d0dc3124507e3393d175ce3ff7c1e96529c6c555ce9e51205e9b2",
    kdf: "pbkdf2",
    kdfparams: {
      c: 262144,
      dklen: 32,
      prf: "hmac-sha256",
      salt: "ae3cd4e7013836a3df6bd7241b12db061dbe2c6785853cce422d148a624ce0bd"
    }
  },
  id: "e13b209c-3b2f-4327-bab0-3bef2e51630d",
  version: 3
}

// asynchronous
keyxpanse.dump(password, dk.privateKey, dk.salt, dk.iv, options, function (keyObject) {
  // do stuff!
});

dump creates an object and not a JSON string. In Node, the exportToFile method provides an easy way to export this formatted key object to file. It creates a JSON file in the keystore sub-directory, and uses gexp's current file-naming convention (ISO timestamp concatenated with the key's derived Expanse address).

keyxpanse.exportToFile(keyObject);

After successful key export, you will see a message like:

Saved to file:
keystore/UTC--2015-08-11T06:13:53.359Z--008aeeda4d805471df9b2a5b0f38a0c3bcba786b

To use with gexp, copy this file to your Expanse keystore folder
(usually ~/.expanse/keystore).

Key import

Importing a key from gexp's keystore can only be done on Node. The JSON file is parsed into an object with the same structure as keyObject above.

// Specify a data directory (optional; defaults to ~/.expanse)
var datadir = "/home/user/.expanse-test";

// Synchronous
var keyObject = keyxpanse.importFromFile(address, datadir);

// Asynchronous
keyxpanse.importFromFile(address, datadir, function (keyObject) {
  // do stuff
});

This has been tested with version 3 and version 1, but not version 2, keys. (Please send me a version 2 keystore file if you have one, so I can test it!)

To recover the plaintext private key from the key object, use keyxpanse.recover. The private key is returned as a Buffer.

// synchronous
var privateKey = keyxpanse.recover(password, keyObject);
// privateKey:
<Buffer ...>

// Asynchronous
keyxpanse.recover(password, keyObject, function (privateKey) {
  // do stuff
});

Hashing rounds

By default, keyxpanse uses 65536 hashing rounds in its key derivation functions, compared to the 262144 gexp uses by default. (keyxpanse's JSON output files are still compatible with gexp, however, since they tell gexp how many rounds to use.) These values are user-editable: keyxpanse.constants.pbkdf2.c is the number of rounds for PBKDF2, and keyxpanse.constants.scrypt.n is the number of rounds for scrypt.

Tests

Unit tests are in the test directory, and can be run with mocha:

npm test

test/gexp.js is an integration test, which is run (along with test/keys.js) using:

npm run gexp

gexp.js generates 1000 random private keys, encrypts each key using a randomly-generated passphrase, dumps the encrypted key info to a JSON file, then spawns a gexp instance and attempts to unlock each account using its passphrase and JSON file. The passphrases are between 1 and 100 random bytes. Each passphrase is tested in both hexadecimal and base-64 encodings, and with PBKDF2-SHA256 and scrypt key derivation functions.

By default, the flags passed to gexp are:

gexp --etherbase <account> --unlock <account> --nodiscover --networkid "10101" --port 30304 --rpcport 8547 --datadir test/fixtures --password test/fixtures/.password

test/fixtures/.password is a file which contains the passphrase. The .password file, as well as the JSON key files generated by gexp.js, are automatically deleted after the test.

(Note: gexp.js conducts 4000 tests, each of which can take up to 5 seconds, so running this file can take up to 5.56 hours.)