authentication-age

An easy-to-use cryptography library slightly inspired by age by Filippo Valsorda (https://github.com/FiloSottile/age), but targeted at a different usecase:

For non-streaming encryption/decryption embedded inside an application. Usecases where the encrypted data is small, like less than a megabyte or so and it's not invoked directly on the command line by a user.

A wrapper around libsodium's functions:

• crypto_pwhash
  • memory-hard key derivation function to turn passwords into encryption key seeds
• crypto_sign_seed_keypair
  • turn encryption key seed into an ed25519 key-pair
• crypto_box_easy
  • A Diffie-Hellman primitive (a way of agreeing on a shared secret using public-private-key cryptography)
• crypto_secretbox_easy
  • A symmetric encryption primitive similar to AES
• crypto_sign
  • A Digital Signature primitive (a way to verify authenticity using public-private-key cryptography)

The purpose of this library: to support encrypting the same file to multiple recipients using public-private-key cryptography, while also supporting the verification of the sender's signature.

API

getKeyPairFromPassphrase(usersPassphrase: string): libsodium.KeyPair

publicKeyToString(publicKey: Uint8Array): string

parsePublicKeyString(publicKeyString: string): Uint8Array

publicKeyToIdentityString(publicKey: Uint8Array): string

createMessage(
  plaintext: string, 
  senderCryptoSignKeyPair: libsodium.KeyPair, 
  recipientCryptoSignPublicKeys: Uint8Array[]
): EncryptedMessage

decryptMessage(
  message: EncryptedMessage, 
  myKeyPair: libsodium.KeyPair, 
  addressBook: AddressBook
): DecryptResult

Usage example:

  const aliceKeyPair = getKeyPairFromPassphrase("alice");
  const bobKeyPair = getKeyPairFromPassphrase("bob");
  const carolKeyPair = getKeyPairFromPassphrase("carol");
  
  const secretMessage = ` Yayyyy!!!! `;

  const encryptedMessage = createMessage(secretMessage, aliceKeyPair, [bobKeyPair.publicKey, carolKeyPair.publicKey]);

  console.log(JSON.stringify(encryptedMessage, null, "  "));

  const addressBook = {
    [publicKeyToIdentityString(aliceKeyPair.publicKey)]: aliceKeyPair.publicKey,
    [publicKeyToIdentityString(bobKeyPair.publicKey)]: bobKeyPair.publicKey,
    [publicKeyToIdentityString(carolKeyPair.publicKey)]: carolKeyPair.publicKey,
  };

  const bobsDecryptedMessage = decryptMessage(encryptedMessage, bobKeyPair, addressBook);

  console.log("bob got: ", JSON.stringify(bobsDecryptedMessage, null, "  "));

  const carolsDecryptedMessage = decryptMessage(encryptedMessage, carolKeyPair, addressBook);

  console.log("carol got: ", JSON.stringify(carolsDecryptedMessage, null, "  "));

EncryptedMessage format

{
  "type": "authenticationage v1",
  "from": "identity_Fy8wD4wYU9mrTuoZKkL73d",
  "to": {
    "identity_L2qurUCyXj2QAnBxkWSKfq": {
      "nonce": "2XNTAPKhukOnxYIOxjYz8_toJBxJVS0S",
      "cryptoBox": "14IR-Qtt2p2IwVBK0rRAGdSrEVonpujo35sPvd9yUXy1RKJ5oB9plkib9mZKK76K"
    },
    "identity_3iSrKmbtm9j41mARd6aAVA": {
      "nonce": "zr3iqJiAb9_u2WZIpRDXRC3OdOMu6YRN",
      "cryptoBox": "DoQ1x0ZF9BmSsxqRERgNjnJPNhJjGD4xqvHVZGcA49yMxYD9kWxEiyY6pIcCM7RA"
    }
  },
  "bodyNonce": "cUJZ1n3esN77cWSAjkZ6wNK9o-b2APt-",
  "bodySecretBox": [
    "ejqKlEVrgOn53_tlC2edIQ47DK0ckxtzedYuw1TOLlvqd-PVjlWykLG2rXT3EFruY4huwyUCe0ar1R",
    "R3ekoKys5bWIapr_At53PDHlXDCjlWNtDY3BWQLQsuCURB5n0JRsg"
  ]
}