🔐 kruptein 
========
crypto (krip-toh); from `kruptein` to hide or conceal.

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🔬 Sandbox
-------
 Here you can experiment with the module to ensure it will suit your needs. [kruptein @ codesandbox.io](https://codesandbox.io/p/devbox/romantic-wu-cywk2c)


🔒 Encrypt
-----------------
An example of creating a new ciphertext object.

```javascript
const kruptein = require("kruptein")(opts || {});
let secret = "S3cre+_Squ1rr3l";

kruptein.set(secret, "Some kind of wonderfully private message", (err, ct) => {
  if (err)
    throw err;

  console.log(ct);
});
```


🔓 Decrypt
------------------
An example of retrieveing plaintext from a ciphertext object.

```javascript
const kruptein = require("kruptein")(opts || {});
let ciphertext, secret = "S3cre+_Squ1rr3l";

kruptein.get(secret, ciphertext, (err, pt) => {
  if (err)
    throw err;

  console.log(pt);
});
```


📦 Install
-------
To install `npm install kruptein`


👓 Methods
-------
*   `.set(secret, plaintext, [aad], callback)`
*   `.get(secret, ciphertext, [{at: auth_tag, aad: aad}], callback)`


🛠️ Options
-------
Industry standards are used for the algorithm, hashing algorithm, key & IV sizes.
The default key derivation function is `pbkdf2`, however use of the `scrypt` or `argon2` can be used as well.

#### Cryptography options
*   `algorithm`: (Optional) Cipher algorithm from `crypto.getCiphers()`. Default: `aes-256-gcm`.
*   `hashing`: (Optional) Hash algorithm from `crypto.getHashes()`. Default: `sha384`.
*   `key_size`: (Optional) Key size bytes (should match block size of algorithm). Default: `32`
*   `iv_size`: (Optional) IV size bytes. Default: `16`.
*   `at_size`: (Optional) Authentication tag size. Applicable to `gcm` & `ocb` cipher modes. Default: `128`.

#### Key derivation options
*   `use_scrypt`: (Optional) Use `.scrypt()` to derive a key. Requires node > v10. Default/Fallback: `.pbkdf2()`.
*   `use_argon2`: (Optional) Use `.argon2id()` to derive a key. Requires node > v24. Default/Fallback: `.pbkdf2()`.

#### Encoding options
*   `encodeas`: (Optional) Output encoding. Currently supports `binary`, `hex`, & `base64`. Default: `base64`.
*   `use_asn1`: (Optional) Disable the default ASN.1 encoding. Default: true


📐 Options example
-----------------
An example of creating a new ciphertext object.

```javascript
const opts = {
  algorithm: 'aes-256-gcm',
  hashing: 'sha384',
  key_size: 64,
  iv_size: 16,
  at_size: 128,
  use_argon2: true,
  encodeas: 'base64',
  use_asn1: true
}

const kruptein = require("kruptein")(opts || {});
```


🗝️ Usage
-----
When selecting an algorithm from `crypto.getCiphers()` the `iv` and `key_size` values are calculated auto-magically to make implementation easy.

You can always define your own if the defaults per algorithm and mode aren't what you would like; see the `options` section above.

The `secret` must meet [complexity requirements](https://github.com/jas-/kruptein/blob/5d41a5fa35101112f150c6bf3f757d660f0f3ce1/lib/kruptein.js#L401)


🌱 Output
------
The `.set()` method output depends on three factors; the `encodeas`, `algorithm` and `use_asn1`.

For any algorithm that supports authentication (AEAD), the object structure includes the `Authentication Tag` and the `Additional
Authentication Data` attribute and value.

When the `use_asn1` option is enabled (default is true), the result is an [ASN.1](https://letsencrypt.org/docs/a-warm-welcome-to-asn1-and-der/) value using the `encodeas` value. While this is a more complex encoding option, it helps standardize & minimize the size of the resulting ciphertext output.


🧪 Test harness
------------
The included test harness, invoked with `npm test`, makes every attempt to trap and handle errors. Some of which come from side channel or possible malability of the resultant ciphertext.

This can be seen within the `test/index.js` CI test harness under the HMAC, AT & AAD validation test cases.


🧠 References
-----------------------
This module conforms to industry recommendations regarding algorithm type, mode, key size, iv size & implementation, digests, key  derivation & management etc. References used provided here:

**RFC:**
*   [RFC 2104](https://tools.ietf.org/html/rfc2104): HMAC: Keyed-Hashing for Message Authentication
*   [RFC 4086](https://tools.ietf.org/html/rfc4086): Randomness Requirements for Security
*   [RFC 5084](https://tools.ietf.org/html/rfc5084): Using AES-CCM and AES-GCM Authenticated Encryption
*   [RFC 7914](https://tools.ietf.org/html/rfc7914): The scrypt Password-Based Key Derivation Function
*   [RFC 8018](https://tools.ietf.org/html/rfc8018): Password-Based Cryptography Specification
*   [RFC 9106](https://datatracker.ietf.org/doc/html/rfc9106): Argon2 Memory-Hard Function for Password Hashing and Proof-of-Work Applications
*   [X.697](https://www.itu.int/rec/T-REC-X.697-201710-I/en): ASN.1 encoding rules: Specifications of JavaScript Object Notation Encoding Rules (JER)


**NIST:**
*   [SP 800-38A](https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-38a.pdf): Block cipher modes of operation
*   [SP 800-38B](https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-38d.pdf): Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC
*   [SP 800-57P1](https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-57pt1r4.pdf): Recommendations for key management
*   [SP 800-107](https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-107r1.pdf): Recommendation for Applications Using Approved Hash Algorithms
*   [SP 800-108](https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-108.pdf): Recommendation for Key Derivation Using Pseudorandom Functions
*   [SP 800-131A](https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-131Ar2.pdf): Transitioning the Use of Cryptographic Algorithms and Key Lengths
*   [SP 800-132](https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-132.pdf): Recommendation for Password-Based Key Derivation
*   [SP 800-175B](https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-175B.pdf): Guideline for Using Cryptographic Standards in the Federal Government


**FIPS:**
*   [FIPS 197](https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.197.pdf): Advanced Encryption Standard (AES)
*   [FIPS 198-1](https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.198-1.pdf): The Keyed-Hash Message Authentication Code (HMAC)
*   [FIPS 180-4](https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.180-4.pdf): Secure Hash Standard (SHS)
*   [FIPS 186-5](https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.186-5.pdf): Digital Signature Standard (DSS)


📡 Contributing
------------
Contributions are welcome & appreciated!

Refer to the [contributing document](https://github.com/jas-/kruptein/blob/master/CONTRIBUTING.md) to help facilitate pull requests.


📑 License
-------
This software is licensed under the [MIT License](https://github.com/jas-/kruptein/blob/master/LICENSE).

Copyright Jason Gerfen, 2019.