nip44: make the api less classy.

nip44.test.ts

@@ -7,7 +7,7 @@ const v2vec = vec.v2
 
 test('get_conversation_key', () => {
   for (const v of v2vec.valid.get_conversation_key) {
-    const key = v2.utils.getConversationKey(v.sec1, v.pub2)
+    const key = v2.utils.getConversationKey(hexToBytes(v.sec1), v.pub2)
     expect(bytesToHex(key)).toEqual(v.conversation_key)
   }
 })
@@ -15,7 +15,7 @@ test('get_conversation_key', () => {
 test('encrypt_decrypt', () => {
   for (const v of v2vec.valid.encrypt_decrypt) {
     const pub2 = bytesToHex(schnorr.getPublicKey(v.sec2))
-    const key = v2.utils.getConversationKey(v.sec1, pub2)
+    const key = v2.utils.getConversationKey(hexToBytes(v.sec1), pub2)
     expect(bytesToHex(key)).toEqual(v.conversation_key)
     const ciphertext = v2.encrypt(v.plaintext, key, hexToBytes(v.nonce))
     expect(ciphertext).toEqual(v.payload)
@@ -39,6 +39,8 @@ test('decrypt', async () => {
 
 test('get_conversation_key', async () => {
   for (const v of v2vec.invalid.get_conversation_key) {
-    expect(() => v2.utils.getConversationKey(v.sec1, v.pub2)).toThrow(/(Point is not on curve|Cannot find square root)/)
+    expect(() => v2.utils.getConversationKey(hexToBytes(v.sec1), v.pub2)).toThrow(
+      /(Point is not on curve|Cannot find square root)/,
+    )
   }
 })

nip44.ts

@@ -4,88 +4,81 @@ import { secp256k1 } from '@noble/curves/secp256k1'
 import { extract as hkdf_extract, expand as hkdf_expand } from '@noble/hashes/hkdf'
 import { hmac } from '@noble/hashes/hmac'
 import { sha256 } from '@noble/hashes/sha256'
-import { concatBytes, randomBytes, utf8ToBytes } from '@noble/hashes/utils'
+import { concatBytes, randomBytes } from '@noble/hashes/utils'
 import { base64 } from '@scure/base'
 
-const decoder = new TextDecoder()
+import { utf8Decoder, utf8Encoder } from './utils.ts'
 
-class u {
+const minPlaintextSize = 0x0001 // 1b msg => padded to 32b
-  static minPlaintextSize = 0x0001 // 1b msg => padded to 32b
+const maxPlaintextSize = 0xffff // 65535 (64kb-1) => padded to 64kb
-  static maxPlaintextSize = 0xffff // 65535 (64kb-1) => padded to 64kb
 
-  static utf8Encode = utf8ToBytes
+export function getConversationKey(privkeyA: Uint8Array, pubkeyB: string): Uint8Array {
-
-  static utf8Decode(bytes: Uint8Array): string {
-    return decoder.decode(bytes)
-  }
-
-  static getConversationKey(privkeyA: string, pubkeyB: string): Uint8Array {
   const sharedX = secp256k1.getSharedSecret(privkeyA, '02' + pubkeyB).subarray(1, 33)
   return hkdf_extract(sha256, sharedX, 'nip44-v2')
-  }
+}
 
-  static getMessageKeys(
+function getMessageKeys(
   conversationKey: Uint8Array,
   nonce: Uint8Array,
-  ): { chacha_key: Uint8Array; chacha_nonce: Uint8Array; hmac_key: Uint8Array } {
+): { chacha_key: Uint8Array; chacha_nonce: Uint8Array; hmac_key: Uint8Array } {
   const keys = hkdf_expand(sha256, conversationKey, nonce, 76)
   return {
     chacha_key: keys.subarray(0, 32),
     chacha_nonce: keys.subarray(32, 44),
     hmac_key: keys.subarray(44, 76),
   }
-  }
+}
 
-  static calcPaddedLen(len: number): number {
+function calcPaddedLen(len: number): number {
   if (!Number.isSafeInteger(len) || len < 1) throw new Error('expected positive integer')
   if (len <= 32) return 32
   const nextPower = 1 << (Math.floor(Math.log2(len - 1)) + 1)
   const chunk = nextPower <= 256 ? 32 : nextPower / 8
   return chunk * (Math.floor((len - 1) / chunk) + 1)
-  }
+}
 
-  static writeU16BE(num: number): Uint8Array {
+function writeU16BE(num: number): Uint8Array {
-    if (!Number.isSafeInteger(num) || num < u.minPlaintextSize || num > u.maxPlaintextSize)
+  if (!Number.isSafeInteger(num) || num < minPlaintextSize || num > maxPlaintextSize)
     throw new Error('invalid plaintext size: must be between 1 and 65535 bytes')
   const arr = new Uint8Array(2)
   new DataView(arr.buffer).setUint16(0, num, false)
   return arr
-  }
+}
 
-  static pad(plaintext: string): Uint8Array {
+function pad(plaintext: string): Uint8Array {
-    const unpadded = u.utf8Encode(plaintext)
+  const unpadded = utf8Encoder.encode(plaintext)
   const unpaddedLen = unpadded.length
-    const prefix = u.writeU16BE(unpaddedLen)
+  const prefix = writeU16BE(unpaddedLen)
-    const suffix = new Uint8Array(u.calcPaddedLen(unpaddedLen) - unpaddedLen)
+  const suffix = new Uint8Array(calcPaddedLen(unpaddedLen) - unpaddedLen)
   return concatBytes(prefix, unpadded, suffix)
-  }
+}
 
-  static unpad(padded: Uint8Array): string {
+function unpad(padded: Uint8Array): string {
   const unpaddedLen = new DataView(padded.buffer).getUint16(0)
   const unpadded = padded.subarray(2, 2 + unpaddedLen)
   if (
-      unpaddedLen < u.minPlaintextSize ||
+    unpaddedLen < minPlaintextSize ||
-      unpaddedLen > u.maxPlaintextSize ||
+    unpaddedLen > maxPlaintextSize ||
     unpadded.length !== unpaddedLen ||
-      padded.length !== 2 + u.calcPaddedLen(unpaddedLen)
+    padded.length !== 2 + calcPaddedLen(unpaddedLen)
   )
     throw new Error('invalid padding')
-    return u.utf8Decode(unpadded)
+  return utf8Decoder.decode(unpadded)
-  }
+}
 
-  static hmacAad(key: Uint8Array, message: Uint8Array, aad: Uint8Array): Uint8Array {
+function hmacAad(key: Uint8Array, message: Uint8Array, aad: Uint8Array): Uint8Array {
   if (aad.length !== 32) throw new Error('AAD associated data must be 32 bytes')
   const combined = concatBytes(aad, message)
   return hmac(sha256, key, combined)
-  }
+}
 
-  // metadata: always 65b (version: 1b, nonce: 32b, max: 32b)
+// metadata: always 65b (version: 1b, nonce: 32b, max: 32b)
-  // plaintext: 1b to 0xffff
+// plaintext: 1b to 0xffff
-  // padded plaintext: 32b to 0xffff
+// padded plaintext: 32b to 0xffff
-  // ciphertext: 32b+2 to 0xffff+2
+// ciphertext: 32b+2 to 0xffff+2
-  // raw payload: 99 (65+32+2) to 65603 (65+0xffff+2)
+// raw payload: 99 (65+32+2) to 65603 (65+0xffff+2)
-  // compressed payload (base64): 132b to 87472b
+// compressed payload (base64): 132b to 87472b
-  static decodePayload(payload: string): { nonce: Uint8Array; ciphertext: Uint8Array; mac: Uint8Array } {
+function decodePayload(payload: string): { nonce: Uint8Array; ciphertext: Uint8Array; mac: Uint8Array } {
   if (typeof payload !== 'string') throw new Error('payload must be a valid string')
   const plen = payload.length
   if (plen < 132 || plen > 87472) throw new Error('invalid payload length: ' + plen)
@@ -105,28 +98,30 @@ class u {
     ciphertext: data.subarray(33, -32),
     mac: data.subarray(-32),
   }
-  }
 }
 
-export class v2 {
+export function encrypt(plaintext: string, conversationKey: Uint8Array, nonce: Uint8Array = randomBytes(32)): string {
-  static utils = u
+  const { chacha_key, chacha_nonce, hmac_key } = getMessageKeys(conversationKey, nonce)
-
+  const padded = pad(plaintext)
-  static encrypt(plaintext: string, conversationKey: Uint8Array, nonce: Uint8Array = randomBytes(32)): string {
-    const { chacha_key, chacha_nonce, hmac_key } = u.getMessageKeys(conversationKey, nonce)
-    const padded = u.pad(plaintext)
   const ciphertext = chacha20(chacha_key, chacha_nonce, padded)
-    const mac = u.hmacAad(hmac_key, ciphertext, nonce)
+  const mac = hmacAad(hmac_key, ciphertext, nonce)
   return base64.encode(concatBytes(new Uint8Array([2]), nonce, ciphertext, mac))
-  }
+}
 
-  static decrypt(payload: string, conversationKey: Uint8Array): string {
+export function decrypt(payload: string, conversationKey: Uint8Array): string {
-    const { nonce, ciphertext, mac } = u.decodePayload(payload)
+  const { nonce, ciphertext, mac } = decodePayload(payload)
-    const { chacha_key, chacha_nonce, hmac_key } = u.getMessageKeys(conversationKey, nonce)
+  const { chacha_key, chacha_nonce, hmac_key } = getMessageKeys(conversationKey, nonce)
-    const calculatedMac = u.hmacAad(hmac_key, ciphertext, nonce)
+  const calculatedMac = hmacAad(hmac_key, ciphertext, nonce)
   if (!equalBytes(calculatedMac, mac)) throw new Error('invalid MAC')
   const padded = chacha20(chacha_key, chacha_nonce, ciphertext)
-    return u.unpad(padded)
+  return unpad(padded)
-  }
 }
 
-export default { v2 }
+export const v2 = {
+  utils: {
+    getConversationKey,
+    calcPaddedLen,
+  },
+  encrypt,
+  decrypt,
+}