RSA and AES Encryption helpers


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01Jun 9, 2021Aug 31, 2018Minified + gzip package size for @anvilco/encryption in KB


Anvil Encryption

This library is a small wrapper around node's crypto library. It offers convenience methods for encrypting and decrypting arbitrary payloads in both AES and RSA.


yarn add @anvilco/encryption

Then use it

// For RSA functions
import { encryptRSA, decryptRSA } from '@anvilco/encryption'

// For AES functions
import { generateAESKey, encryptAES, decryptAES } from '@anvilco/encryption'

// Could grab the keys from file (or preferably from environment variables)
import fs from 'fs'
const privateKey = fs.readFileSync('path/to/privateKey.pem')
const publicKey = fs.readFileSync('path/to/publicKey.pem')

// RSA
const message = 'Super secret message'
const encryptedRSAMessage = encryptRSA(publicKey, message)
const origRSAMessage = decryptRSA(privateKey, encryptedRSAMessage)
console.log(origRSAMessage === message) // => true

// AES
const aesKey = generateAESKey()
const encryptedAESMessage = encryptAES(aesKey, message)
const origAESMessage = decryptAES(aesKey, encryptedAESMessage)
console.log(origAESMessage === message) // => true


There are two functions for RSA: encryptRSA, decryptRSA, and three for AES: generateAESKey, encryptAES, decryptAES.


There are three functions for AES:

  • key = generateAESKey()
  • encryptedMessage = encryptAES(key, plainMessage)
  • plainMessage = decryptAES(key, encryptedMessage)

encryptAES creates a unique IV for each message encrypted and prepends it to the resulting encrypted payload. So encryptedMessage will be in the format



There are two functions for RSA:

  • encryptedMessage = encryptRSA(publicKey, plainMessage)
  • plainMessage = decryptRSA(privateKey, encryptedMessage)

These functions encrypt / decrypt with RSA and AES. RSA has an upper limit on how much data it can encrypt. So we create an AES key, encrypt the AES key with RSA, then encrypt the actual message with AES.

Note the encrypted payload (result of encryptRSA) is in the format:


Generating RSA keys

This library does not have a way to generate RSA keys.

You could use openssl:

# This generates a 2048 bit private key to file
openssl genrsa -out privateKey.pem 2048

# This extracts the public key to file
openssl rsa -in privateKey.pem -outform PEM -pubout -out publicKey.pem

You could also use something like node-rsa:

// Example generating a RSA keypair with node-rsa
import NodeRSA from 'node-rsa'
function generateRSAKeypair () {
  const key = new NodeRSA()
  key.generateKeyPair(2048, 65537)
  return {
    publicKey: key.exportKey('pkcs8-public-pem'),
    privateKey: key.exportKey('pkcs8-private-pem'),



If you find any bugs or have a feature request, please open an issue on github!

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