NIP-44

ChaCha20 authenticated encryption with HMAC-SHA256 and padding.

Import

import { nip44 } from 'nostr-core'

nip44.getConversationKey

function getConversationKey(
  privkeyA: Uint8Array,
  pubkeyB: string
): Uint8Array

Pre-computes a shared conversation key using ECDH + HKDF-SHA256.

Parameter	Type	Description
privkeyA	Uint8Array	Your secret key (32 bytes)
pubkeyB	string	Other party's public key (64-char hex)

Returns: Uint8Array - 32-byte conversation key.

Compute this once per conversation partner and reuse it for all messages.

const convKey = nip44.getConversationKey(mySecretKey, recipientPubkey)

nip44.encrypt

function encrypt(
  plaintext: string,
  conversationKey: Uint8Array,
  nonce?: Uint8Array
): string

Encrypts a message with ChaCha20 and authenticates with HMAC-SHA256.

Parameter	Type	Description
plaintext	string	Message to encrypt
conversationKey	Uint8Array	Pre-computed conversation key
nonce	Uint8Array?	32-byte nonce (random if omitted)

Returns: string - base64-encoded payload.

The payload format is: [version(1), nonce(32), ciphertext(?), mac(32)].

const convKey = nip44.getConversationKey(mySecretKey, recipientPubkey)
const payload = nip44.encrypt('Hello!', convKey)

nip44.decrypt

function decrypt(
  payload: string,
  conversationKey: Uint8Array
): string

Decrypts and verifies a NIP-44 encrypted payload.

Parameter	Type	Description
payload	string	Base64-encoded encrypted payload
conversationKey	Uint8Array	Pre-computed conversation key

Returns: string - decrypted plaintext.

Throws: Error on:

• Invalid base64 encoding
• Unsupported version (must be 2)
• MAC verification failure
• Invalid padding

const convKey = nip44.getConversationKey(mySecretKey, senderPubkey)
const plaintext = nip44.decrypt(payload, convKey)

How It Works

1. Derives a shared point via ECDH
2. Extracts a 32-byte conversation key with HKDF (salt: nip44-v2)
3. Pads the plaintext to the next power of 2 (min 32 bytes) with a 2-byte length prefix
4. Derives per-message keys from the conversation key + nonce using HKDF-expand:
   • chacha_key (32 bytes)
   • chacha_nonce (12 bytes)
   • hmac_key (32 bytes)
5. Encrypts with ChaCha20
6. Computes HMAC-SHA256 over nonce || ciphertext
7. Encodes as version || nonce || ciphertext || mac in base64