nip44 updates (#278)

Co-authored-by: Jonathan Staab <shtaab@gmail.com>

nip44.test.ts

@@ -1,6 +1,7 @@
 import crypto from 'node:crypto'
+import {hexToBytes} from '@noble/hashes/utils'
 
-import {encrypt, decrypt} from './nip44.ts'
+import {encrypt, decrypt, getSharedSecret} from './nip44.ts'
 import {getPublicKey, generatePrivateKey} from './keys.ts'
 
 // @ts-ignore
@@ -12,8 +13,9 @@ test('encrypt and decrypt message', async () => {
   let sk2 = generatePrivateKey()
   let pk1 = getPublicKey(sk1)
   let pk2 = getPublicKey(sk2)
+  let sharedKey1 = getSharedSecret(sk1, pk2)
+  let sharedKey2 = getSharedSecret(sk2, pk1)
 
-  expect(await decrypt(sk2, pk1, await encrypt(sk1, pk2, 'hello'))).toEqual(
-    'hello'
-  )
+  expect(decrypt(hexToBytes(sk1), encrypt(hexToBytes(sk1), 'hello'))).toEqual('hello')
+  expect(decrypt(sharedKey2, encrypt(sharedKey1, 'hello'))).toEqual('hello')
 })

nip44.ts

@@ -6,51 +6,40 @@ import {xchacha20} from '@noble/ciphers/chacha'
 
 import {utf8Decoder, utf8Encoder} from './utils.ts'
 
-// @ts-ignore
-if (typeof crypto !== 'undefined' && !crypto.subtle && crypto.webcrypto) {
-  // @ts-ignore
-  crypto.subtle = crypto.webcrypto.subtle
-}
-
 export const getSharedSecret = (privkey: string, pubkey: string): Uint8Array =>
   sha256(secp256k1.getSharedSecret(privkey, '02' + pubkey).subarray(1, 33))
 
-export function encrypt(privkey: string, pubkey: string, text: string, v = 1) {
+export function encrypt(key: Uint8Array, text: string, v = 1) {
   if (v !== 1) {
     throw new Error('NIP44: unknown encryption version')
   }
 
-  const key = getSharedSecret(privkey, pubkey)
   const nonce = randomBytes(24)
   const plaintext = utf8Encoder.encode(text)
   const ciphertext = xchacha20(key, nonce, plaintext)
 
-  return JSON.stringify({
-    ciphertext: base64.encode(ciphertext),
-    nonce: base64.encode(nonce),
-    v
-  })
+  const payload = new Uint8Array(25 + ciphertext.length)
+  payload.set([v], 0)
+  payload.set(nonce, 1)
+  payload.set(ciphertext, 25)
+
+  return base64.encode(payload)
 }
 
-export function decrypt(privkey: string, pubkey: string, payload: string) {
+export function decrypt(key: Uint8Array, payload: string) {
   let data
   try {
-    data = JSON.parse(payload) as {
-      ciphertext: string
-      nonce: string
-      v: number
-    }
+    data = base64.decode(payload)
   } catch (e) {
-    throw new Error('NIP44: failed to parse payload')
+    throw new Error(`NIP44: failed to base64 decode payload: ${e}`)
   }
 
-  if (data.v !== 1) {
-    throw new Error('NIP44: unknown encryption version')
+  if (data[0] !== 1) {
+    throw new Error(`NIP44: unknown encryption version: ${data[0]}`)
   }
 
-  const key = getSharedSecret(privkey, pubkey)
-  const nonce = base64.decode(data.nonce)
-  const ciphertext = base64.decode(data.ciphertext)
+  const nonce = data.slice(1, 25)
+  const ciphertext = data.slice(25)
   const plaintext = xchacha20(key, nonce, ciphertext)
 
   return utf8Decoder.decode(plaintext)