vault-cipher

Provides a high-level authenticated encryption API that Vault uses to encrypt its stored settings. On Node, it's backed by the crypto module, while in the browser it uses asmCrypto. Random values are generated with crypto.randomBytes() or crypto.getRandomValues() where available.

The encryption algorithm is an encrypt-then-MAC scheme based on AES and HMAC.

• The given secret is used to derive an encryption key and a signing key using PBKDF2
• The plaintext is padded to a multiple of the AES block size using PKCS#7
• A random iv is selected using crypto.randomBytes()
• The plaintext is encrypted using AES-256-CBC with the encryption key and iv to produce ciphertext
• iv and ciphertext are concatenated and signed using HMAC-SHA-256 with the signing key to produce mac
• The result is the concatenation of iv, ciphertext and mac

+--------+      +--------+      +----------------+----------------+
| secret |----->| PBKDF2 |----->| encryption key |  signing key   |
+--------+      +--------+      +----------------+----------------+
                                    |                     |
+---------+                         V                     |
| message |------------------>+-------------+             |
+---------+     +----+        | AES-256-CBC |             |
                | iv |------->+-------------+             |
                +----+              |                     |
                   |                |                     |
                   V                V                     V
              +----------+------------------+     +--------------+
              |    iv    |    ciphertext    |---->| HMAC-SHA-256 |
              +----------+------------------+     +--------------+
                      |               |                 |
                      V               V                 V
                  +----------+------------------+-----------+
                  |    iv    |    ciphertext    |    mac    |
                  +----------+------------------+-----------+

Its high-level API provides a simple way to encrypt and decrypt text:

var Cipher = require('vault-cipher'),
    cipher = new Cipher('your secret key');

var ciphertext = cipher.encrypt('some text');

cipher.decrypt(ciphertext) // -> 'some text'

Settings

The cipher is configurable by passing options to the constructor, for example:

var cipher = new Cipher('secret key', { format: 'hex', work: 1000 })

The available options are:

• format: the output format of the ciphertext, either base64 (default) or hex
• salt: a salt string used during PBKDF2 key derivation, defaults to a GUID embedded in the library
• work: the number of PBKDF2 iterations used to derive the encryption and signing keys, default is 10,000