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Secure secret storage and cryptographic key retrieval for Node.js

var cryptex = require('cryptex')
cryptex.getSecret('mySQLPass').then(function(pass) {
  conn = mysql.connect({
    username: user,
    password: pass,
    host: hostname

Keep your secrets secret!

If you check database passwords into git, download credential files from S3 or some other server, provide plaintext keys to your continuous integration/deployment solution, or don't have the ability to limit engineers from getting production secrets, stop doing what you're doing.

Cryptex is here to help. Here's how:

1. Pick a configuration method

There are three ways to set up Cryptex. Use what works best for your project:

cryptex.json in your app root

Set up cryptex in different ways automatically depending on what the NODE_ENV environment variable is set to. The file looks like this:

  "production": {
    "keySource": "kms",
    "keySourceOpts": {
      "dataKey": "kms+encrypted+base64+string=="
  "development": {
    "keySource": "none",
    "algorithm": "plaintext",
    "secretEncoding": "utf8",
    "secrets": {
      "mySQLPass": "devlocal"

Put it right in the code

Don't want clutter in your file tree? That's cool. Do this:

  config: {
    keySource: 'kms',
    keySourceOpts: {
      dataKey: 'kms+encrypted+base64+string=='

Throw it all in environment variables

Following 12 Factor? Rock on. We have env var support already built-in.


2. Pick a key source

Cryptex encrypts all of your secrets with a key. You don't want that key shared with anyone in plaintext, no matter how much you trust them. Cryptex will request your key when it's needed and delete it from RAM afterward. Here are the available sources:

Amazon KMS ("kms")

Amazon Web Services' Key Management System is the most secure and easy-to-implement key source. If you already have an AWS account, KMS is cheap and easy to use. Create an encryption key using the IAM console, and note the alias you gave it. Install the AWS CLI tool and run this command with your key alias to get an encrypted AES256 key:

aws kms generate-data-key-without-plaintext \
  --key-id alias/YOUR_KEY_ALIAS \
  --key-spec AES_256 \
  --output text \
  --query CiphertextBlob
kms options:

dataKey CRYPTEX_KEYSOURCE_KMS_PATH: The base64 string you got when you ran that command above.
region CRYPTEX_KEYSOURCE_KMS_REGION: The AWS region (such as us-east-1) in which the master KMS key can be found. If not specified, the config already loaded into aws-sdk is used.

A note about aws-sdk configuration: The KMS keySource uses Amazon's official Node.js aws-sdk library. If you're using npm>=3, it will use the same object as any you might have in your local project, carrying over the configuration. Otherwise, please see Amazon's guide on configuring the SDK to provide it with credentials. The highly recommended way to allow it to access KMS in production (assuming it's in production on AWS servers) is to attach an IAM role to the EC2 node with permission to access the master key you're using.

Load from file ("file")

If your secure key is available in a file, use this method. Note, however, that it is your responsibility to make sure that key file stays secure and inaccessible to prying eyes!

Is your key file something other than binary-encoded? Set keySourceEncoding in your config, or set the CRYPTEX_KEYSOURCEENCODING environment variable, to either base64 or hex.

file options:

path CRYPTEX_KEYSOURCE_FILE_PATH: The path to the key file

Download via http(s) ("http")


If you're using anything other than an https URL in production, you're definitely doing it wrong. You'll need to be an expert in locking your key server down for this to be anywhere near secure.

As with file, if your key file is something other than binary-encoded, set keySourceEncoding in your config, or set the CRYPTEX_KEYSOURCEENCODING environment variable, to either base64 or hex.

http options:

url CRYPTEX_KEYSOURCE_HTTP_URL: The URL to the key file to download
timeout CRYPTEX_KEYSOURCE_HTTP_TIMEOUT: The number of milliseconds after which to fail the download. (Default: 4000)

Plain text ("plaintext")


Useful for local development and testing, this allows the key to be saved in plain text. You'll also want to set keySourceEncoding in your config (or the CRYPTEX_KEYSOURCEENCODING environment variable) to either base64 or hex -- however you've stringified your key.

plaintext options:

key CRYPTEX_KEYSOURCE_PLAINTEXT_KEY: Your key, in plain text

No key ("none")

This is useful if you're plugging in an algorithm that doesn't require a pre-set key to be used.

3. Pick an encryption algorithm

The recommended and default algorithm is aes256. If you're good with that, move on! You don't even need to set algorithm in your config or the CRYPTEX_ALGORITHM environment variable. But for the sake of completeness:

AES 256-bit ("aes256")

Military-grade symmetric encryption. The implementation in Cryptex computes a new random 128-bit initialization vector for each encrypted secret. Obviously, to use this, the key provided by your keySource must be a 256-bit AES key.

Plain text ("plaintext")


Useful for local development. With this, no keySource is needed and all secrets can be stored in plain text. Remember to set secretEncoding in your config, or the CRYPTEX_SECRETENCODING environment variable, to utf8.

4. Secure your secrets

If you installed Cryptex globally, you'll have a CLI tool called cryptex that can encrypt and decrypt your keys according to your cryptex.json or environment variables. It's this easy:

$ cryptex encrypt mypassword

To specify a particular node environment (for cryptex.json users), pass it in the -e flag. Run cryptex --help for all the details.

5. Save your secrets

Provide your secrets to production by either putting them in your config like this...

// cryptex.json
"production": {
  "keySource": "kms",
  "keySourceOpts": {
    "dataKey": "kms+encrypted+base64+string=="
  "secrets": {
    "mySQLPass": "Q+JfrQS5DtSjqWHu1oO4HqctA2hVw4VhaDQfBCuvO8U="

...or by saving them in uppercase environment variables prefixed by CRYPTEX_SECRET_:



First, grab an instance:

var cryptex = require('cryptex')
new cryptex.Cryptex(opts = {})

Creates a new Cryptex instance with the specified options. See the update function below for an option list.

cryptex.encrypt(data: string|Buffer, encoding = "utf8"): string

Encrypts the given data into a base64 string. If your string is binary data encoded as base64 or hex, just pass base64 or hex for the encoding. The encoding is ignored if a Buffer is passed in.

cryptex.decrypt(data: string|Buffer, encoding = "base64"): string

Decrypts the given data and passes it back as utf8. If your string is binary data encoded as base64 or hex, just pass base64 or hex for the encoding. The encoding is ignored if a Buffer is passed in.

cryptex.getSecret(secret: string, optional = false): Promise<string>|null

Gets a Promise that resolves to a pre-saved secret, decrypted. See step 5 above. If no secret of the given name was found, this function with reject by default. To have it resolve with null instead, set optional to true.

cryptex.getSecrets(secrets: Array<string>, optional = false): Promise<Object>

Gets a Promise that resolves to an object mapping the requested secret names to their decrypted values. Unlike calling getSecret multiple times, this function will wait for the key to be cached (if enabled) from decrypting the first secret before decrypting the rest. This provides a faster and more efficient delivery of multiple secrets. If optional is set to true, any requested secrets not found will have their values in the object map set to null. Otherwise, the returned Promise will be rejected.

cryptex.update(opts = {})

Updates the cryptex instance with new configuration. Available options are:

file: The path to a json file to load, mapping environments names (as pulled from $NODE_ENV) to configuration objects. Can also be set in CRYPTEX_FILE. Defaults to cryptex.json in the app process's current working directory.

env: The environment to select from the specified json file. Cryptex will attempt to pull an environment in this order: This value, the CRYPTEX_ENV env var, the NODE_ENV env var, or default to default if all else has failed.

cacheKey: Boolean true to cache the key returned by the keySource in RAM, false to pull the key from the source every time it's needed. Can also be set in CRYPTEX_CACHEKEY with "true" or "false". (Default: true)

cacheTimeout: If cacheKey is true, the number of milliseconds after which to delete the key and allow the Node.js garbage collector to remove it from RAM. Set to 0 to disable the timeout (NOT RECOMMENDED). Can also be set in CRYPTEX_CACHETIMEOUT. (Default: 5000)

config: A configuration object specifying the keySource and other information outlined above. If this is set, Cryptex will not attempt to load a configuration file, and the environment setting is ignored. Set config to {} to force all configuration to be set in environment variables.


Get it global and local for the super convenient command-line tool:

npm install -g cryptex
npm install --save cryptex


Cryptex uses ES6 native Promises, available in Node.js version 0.12 and up.

Security warning

The state of cryptographic security in Javascript is abysmal at best. Node lends itself to far better possibilities than what you'd find in the browser, but be aware of the following types of attacks:

  • Javascript modules that require('cryptex') or some other portion of your code, overriding getSecret or other functions to steal your decrypted private data.
  • Javascript modules that require('crypto') and monkey-patch the built-in Node library to steal private data.
  • Nefarious applications that dump the RAM from your Node process. Node's garbage collector cannot be forced to run from Javascript, so even turning off the key cache could expose a window in which an unencrypted key could be stolen.
  • Applications, server users, or javascript modules that read local key files. When in doubt, use Amazon KMS.

This article by NCC Group is from 2011 and focuses on the security of Javascript in the browser, but is still very much applicable today. However, by using Amazon KMS, Cryptex, and with careful review of all installed modules, a secure system in Node.js is possible.


Embassy supports Node 4 LTE and higher out of the box. For 0.12, consider compiling with Babel.


Cryptex is released under the ultra-permissive ISC license. See LICENSE.txt for details.


Cryptex was originally created at TechnologyAdvice in Nashville, TN.

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