feat: NIP-44 (v2) encrypt/decrypt for window.nostr

CHANGELOG.md

@@ -5,6 +5,18 @@ All notable changes to Podkey will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Added
+
+- **NIP-44 (v2) encryption** — `window.nostr.nip44.encrypt(pubkey, plaintext)`
+  and `window.nostr.nip44.decrypt(pubkey, ciphertext)`, enabling NIP-17 / NIP-59
+  gift-wrapped direct messages. Crypto runs in the background service worker
+  (the private key never reaches the page), reusing the existing message-passing
+  path. Implemented with `@noble/ciphers` (chacha20) + `@noble/hashes`
+  (hkdf/hmac/sha256) + `@noble/secp256k1` (ECDH). Verified against the official
+  NIP-44 spec test vectors.
+
 ## [0.0.7] - 2024-12-XX
 
 ### Changed

README.md

@@ -68,6 +68,7 @@
 - ✅ **Key Generation** - Secure cryptographic key generation using `@noble/secp256k1`
 - ✅ **Key Import** - Import existing 64-char hex private keys
 - ✅ **Event Signing** - Sign Nostr events with Schnorr signatures
+- ✅ **NIP-44 Encryption** - v2 `encrypt`/`decrypt` for NIP-17/NIP-59 gift-wrapped DMs (key never leaves the background)
 - ✅ **Trust Management** - Per-origin permissions with auto-approval
 - ✅ **Beautiful UI** - Soft gradients, smooth animations
 - ✅ **64-char Hex Keys** - Proper did:nostr format compatibility
@@ -261,6 +262,19 @@ const signed = await window.nostr.signEvent({
 })
 ```
 
+### `window.nostr.nip44.encrypt(pubkey, plaintext)` / `window.nostr.nip44.decrypt(pubkey, ciphertext)`
+
+NIP-44 (v2) encryption, used by NIP-17 / NIP-59 gift-wrapped direct messages.
+The private key never leaves the background service worker — encryption is
+performed there and only the resulting base64 payload (or decrypted plaintext)
+crosses to the page, mirroring the existing signing message path.
+
+```javascript
+const peer = '<64-char hex pubkey>'
+const payload = await window.nostr.nip44.encrypt(peer, 'hello')
+const plaintext = await window.nostr.nip44.decrypt(peer, payload)
+```
+
 ### `window.nostr.getRelays()`
 
 Returns relay configuration (coming soon).

package.json

@@ -34,6 +34,7 @@
   },
   "homepage": "https://github.com/JavaScriptSolidServer/podkey#readme",
   "dependencies": {
+    "@noble/ciphers": "^2.2.0",
     "@noble/hashes": "^1.3.3",
     "@noble/secp256k1": "^3.0.0"
   },
@@ -44,4 +45,4 @@
   "engines": {
     "node": ">=18.0.0"
   }
-}
+}

src/background.js

@@ -4,6 +4,12 @@
  */
 
 import { generateKeypair, signEvent, getPublicKey } from './crypto.js';
+import {
+  getConversationKey,
+  encrypt as nip44Encrypt,
+  decrypt as nip44Decrypt,
+  bytesToHex as nip44BytesToHex
+} from './nip44.js';
 import {
   storeKeypair,
   getKeypair,
@@ -83,6 +89,15 @@ async function handleMessage (message, sender) {
     case 'NIP04_DECRYPT':
       throw new Error('NIP-04 encryption not yet implemented');
 
+    case 'NIP44_ENCRYPT':
+      return await handleNip44Encrypt(message.pubkey, message.plaintext, origin);
+
+    case 'NIP44_DECRYPT':
+      return await handleNip44Decrypt(message.pubkey, message.ciphertext, origin);
+
+    case 'NIP44_GET_CONVERSATION_KEY':
+      return await handleNip44GetConversationKey(message.pubkey, origin);
+
     case 'CREATE_NIP98_AUTH_HEADER':
       return await createNip98AuthHeader(
         message.url,
@@ -181,6 +196,90 @@ async function handleSignEvent (event, origin, sender) {
   };
 }
 
+/**
+ * Resolve the user's keypair for an encryption request, gating on origin
+ * trust exactly the way GET_PUBLIC_KEY / SIGN_EVENT do. The raw private key
+ * never leaves the background service worker — only ciphertext/plaintext or a
+ * conversation key is returned to the page.
+ *
+ * @param {string} origin - requesting page origin
+ * @param {string} action - human-readable action for the permission prompt
+ * @returns {Promise<{privateKey: string, publicKey: string}>}
+ */
+async function resolveKeypairForEncryption (origin, action) {
+  const keyExists = await hasKeypair();
+  if (!keyExists) {
+    throw new Error('No keypair found. Please generate or import a key first.');
+  }
+
+  const trusted = await isTrustedOrigin(origin);
+  if (!trusted) {
+    const allowed = await showPermissionPrompt(origin, action);
+    if (!allowed) {
+      throw new Error('User denied permission');
+    }
+    await addTrustedOrigin(origin);
+  }
+
+  const keypair = await getKeypair();
+  if (!keypair || typeof keypair.privateKey !== 'string') {
+    throw new Error('Invalid keypair format');
+  }
+  return keypair;
+}
+
+/**
+ * NIP-44 (v2) encrypt: encrypt plaintext for a peer pubkey.
+ * @param {string} peerPubkey - 64-char hex peer public key
+ * @param {string} plaintext - message to encrypt
+ * @param {string} origin - requesting page origin
+ * @returns {Promise<string>} base64 NIP-44 payload
+ */
+async function handleNip44Encrypt (peerPubkey, plaintext, origin) {
+  if (typeof peerPubkey !== 'string' || typeof plaintext !== 'string') {
+    throw new Error('nip44.encrypt requires (pubkey, plaintext) strings');
+  }
+
+  const keypair = await resolveKeypairForEncryption(origin, 'encrypt a message (NIP-44)');
+  const conversationKey = getConversationKey(keypair.privateKey, peerPubkey);
+  return nip44Encrypt(plaintext, conversationKey);
+}
+
+/**
+ * NIP-44 (v2) decrypt: decrypt a base64 payload from a peer pubkey.
+ * @param {string} peerPubkey - 64-char hex peer public key
+ * @param {string} ciphertext - base64 NIP-44 payload
+ * @param {string} origin - requesting page origin
+ * @returns {Promise<string>} decrypted plaintext
+ */
+async function handleNip44Decrypt (peerPubkey, ciphertext, origin) {
+  if (typeof peerPubkey !== 'string' || typeof ciphertext !== 'string') {
+    throw new Error('nip44.decrypt requires (pubkey, ciphertext) strings');
+  }
+
+  const keypair = await resolveKeypairForEncryption(origin, 'decrypt a message (NIP-44)');
+  const conversationKey = getConversationKey(keypair.privateKey, peerPubkey);
+  return nip44Decrypt(ciphertext, conversationKey);
+}
+
+/**
+ * NIP-44 (v2) conversation key derivation (hex). Some apps call this sub-API to
+ * cache the key client-side; we still derive it in the background so the raw
+ * private key stays here.
+ * @param {string} peerPubkey - 64-char hex peer public key
+ * @param {string} origin - requesting page origin
+ * @returns {Promise<string>} 64-char hex conversation key
+ */
+async function handleNip44GetConversationKey (peerPubkey, origin) {
+  if (typeof peerPubkey !== 'string') {
+    throw new Error('nip44.getConversationKey requires a pubkey string');
+  }
+
+  const keypair = await resolveKeypairForEncryption(origin, 'derive a NIP-44 conversation key');
+  const conversationKey = getConversationKey(keypair.privateKey, peerPubkey);
+  return nip44BytesToHex(conversationKey);
+}
+
 /**
  * Generate new keypair
  */