aes256gcm-bundle

A simple way to encrypt/decrypt fields to/from a string bundle, using AES256-GCM with a randomly generated IV.

---

Installation

``bash

npm i aes256gcm-bundle

`

---

Encrypt / Decrypt


`typescript

import CipherBundle from 'aes256gcm-bundle'

const cb = new CipherBundle(base64urlEncodedKey)

const bundle = cb.encrypt('Hello world')

// e.g.: "0.YFG9joOntVvgLLYQ.QL7k4BFI8ot8PJeqTXOyXQ.fQGNGGwvoKEQXg0"

const plainText = cb.decrypt(bundle)

// e.g.: "Hello world"


`

---

Creating a CipherBundle


use a randomly generated base64url-encoded key (very secure)
`typescript

import crypto from 'node:crypto'
const key = crypto.randomBytes(32).toString('base64url')
// example key: Bi-zMjDdm8ZuqbJQ5WstSwFUCLwVwsPcBQvah-pprSY

let cb = new CipherBundle(key)

`

or provide a key in another encoding (utf8, base64, hex, ...)
`typescript

cb = new CipherBundle(veryStrongPassword, 'utf8')

`

---

Bundle format

Text passed to encrypt() creates a bundle in this dot-separated format: keyName.iv.authTag.cipherText.

Example bundle:

prod1.2N6zOPNuH-3C8vFY.ZGhXywwmEgf14YR2shaiqQ.TIK7rtKvcqrEjG4

$3

- The keyName is just a moniker that is set to 0 by default, but you can override it to denote (to you) which key was used to encrypt the bundle. It can be set to a meaningful value (e.g. prod0) and should be changed when rotating keys.

- The iv and authTag components are opaque base64url-encoded values that are needed to successfully decrypt the bundle.

- The cipherText component of the bundle is the AES256-GCM encryption of the plain text (with a random IV), encoded to a base64url string.
The key used for encryption is the SHA-256 of the key that you provide when creating a CipherBundle (described below).

---

Key rotation / identification

To support key rotation/identification, you can pass an optional keyName parameter to encrypt(text, keyName). The default prefix is 0 when keyName is not specified. The keyName parameter changes the prefix on your bundle to a tag that allows you to later identify which key was used to encrypt the bundle, under your own naming conventions. The name should be short but meaningful (example prod1), cannot include the . character, and should be changed alongside a key rotation (e.g. to prod2).

It is up to you to determine an appropriate key rotation schedule - after a billion encryptions with the same key, it is probably time to choose a new key!
Since the IV is randomly generated, there is a very small chance of a duplicate IV after many encryptions - this is significant known risk for AES256-GCM,
but it can be mitigated by periodic key rotations.

Here is an example of setting a custom prefix for the bundle to identify the use of a new key:

`typescript

cb = new CipherBundle(prod1Key)

const bundle = cb.encrypt('Hello world', "prod1")

// example bundle: prod1.VqUyV8dr33MRITD5.7LiH24gOXaoGHw9sfJMNKA.r00A78iuZWNd748

const plainText = cb.decrypt(bundle)

// example plainText: Hello world

``