max keys 256.

.eslintrc.json

@@ -22,6 +22,7 @@
 
   "globals": {
     "document": false,
+    "BigInt": false,
     "navigator": false,
     "window": false,
     "crypto": false,

event.ts

@@ -13,6 +13,7 @@ export enum Kind {
   EncryptedDirectMessage = 4,
   EventDeletion = 5,
   Reaction = 7,
+  StatelessRevocation = 13,
   ChannelCreation = 40,
   ChannelMetadata = 41,
   ChannelMessage = 42,

index.ts

@@ -12,6 +12,7 @@ export * as nip10 from './nip10'
 export * as nip19 from './nip19'
 export * as nip26 from './nip26'
 export * as nip39 from './nip39'
+export * as nip41 from './nip41'
 export * as nip57 from './nip57'
 
 export * as fj from './fakejson'

nip41.test.js

@@ -0,0 +1,154 @@
+/* eslint-env jest */
+
+const secp256k1 = require('@noble/secp256k1')
+const {
+  getPublicKey,
+  validateEvent,
+  verifySignature,
+  generatePrivateKey,
+  nip41
+} = require('./lib/nostr.cjs')
+
+test('sanity', () => {
+  let sk = generatePrivateKey()
+
+  expect(getPublicKey(sk)).toEqual(secp256k1.Point.fromPrivateKey(sk).toHexX())
+})
+
+test('key arithmetics', () => {
+  expect(
+    secp256k1.utils.mod(secp256k1.CURVE.n + 1n, secp256k1.CURVE.n)
+  ).toEqual(1n)
+
+  let veryHighPoint = secp256k1.Point.fromPrivateKey(
+    (secp256k1.CURVE.n - 1n).toString(16).padStart(64, '0')
+  )
+  let pointAt2 = secp256k1.Point.fromPrivateKey(
+    2n.toString(16).padStart(64, '0')
+  )
+  let pointAt1 = secp256k1.Point.fromPrivateKey(
+    1n.toString(16).padStart(64, '0')
+  )
+  expect(veryHighPoint.add(pointAt2)).toEqual(pointAt1)
+
+  expect(
+    secp256k1.getPublicKey(1n.toString(16).padStart(64, '0'), true)
+  ).toEqual(pointAt1.toRawBytes(true))
+})
+
+test('testing getting child keys compatibility', () => {
+  let sk = '2222222222222222222222222222222222222222222222222222222222222222'
+  let pk = secp256k1.getPublicKey(sk, true)
+  let hsk = '3333333333333333333333333333333333333333333333333333333333333333'
+  let hpk = secp256k1.getPublicKey(hsk, true)
+
+  expect(secp256k1.utils.bytesToHex(nip41.getChildPublicKey(pk, hpk))).toEqual(
+    secp256k1.utils.bytesToHex(
+      secp256k1.getPublicKey(nip41.getChildPrivateKey(sk, hsk), true)
+    )
+  )
+})
+
+test('more testing child key derivation', () => {
+  ;[
+    {
+      sk: '448aedc74f93b71af69ed7c6860d95f148d796355517779c7631fdb64a085b26',
+      hsk: '00ee15a0a117e818073b92d7f3360029f6e091035534348f713a23d440bd8f58',
+      pk: '02e3990b0eb40452a8ffbd9fe99037deb7beeb6ab26020e8c0e8284f3009a56d0c',
+      hpk: '029e9cb07f3a3b8abcad629920d4a5460aefb6b7c08704b7f1ced8648b007ef65f'
+    },
+    {
+      sk: '778aedc74f93b71af69ed7c6860d95f148d796355517779c7631fdb64a085b26',
+      hsk: '99ee15a0a117e818073b92d7f3360029f6e091035534348f713a23d440bd8f58',
+      pk: '020d09894e321f53a7ac8bc003cb1563a4857d57ea69c39ab7189e2cccedc17d1b',
+      hpk: '0358fe19e14c78c4a8c0037a2b9d3e3a714717f2a2d8dd54a5e88d283440dcb28a'
+    },
+    {
+      sk: '2eb5edc74f93b71af69ed7c6860d95f148d796355517779c7631fdb64a085b26',
+      hsk: '65d515a0a117e818073b92d7f3360029f6e091035534348f713a23d440bd8f58',
+      pk: '03dd651a07dc6c9a54b596f6492c9623a595cb48e31af04f8c322d4ce81accb2b0',
+      hpk: '03b8c98d920141a1e168d21e9315cf933a601872ebf57751b30797fb98526c2f4f'
+    }
+  ].forEach(({pk, hpk, sk, hsk}) => {
+    expect(
+      secp256k1.utils.bytesToHex(secp256k1.getPublicKey(sk, true))
+    ).toEqual(pk)
+    expect(
+      secp256k1.utils.bytesToHex(secp256k1.getPublicKey(hsk, true))
+    ).toEqual(hpk)
+
+    expect(
+      secp256k1.utils.bytesToHex(
+        nip41.getChildPublicKey(
+          secp256k1.utils.hexToBytes(pk),
+          secp256k1.utils.hexToBytes(hpk)
+        )
+      )
+    ).toEqual(
+      secp256k1.utils.bytesToHex(
+        secp256k1.getPublicKey(nip41.getChildPrivateKey(sk, hsk), true)
+      )
+    )
+  })
+})
+
+test('generating a revocation event and validating it', () => {
+  const mnemonic =
+    'air property excess weird rare rival fade intact brave office mirror wait'
+
+  const firstKey = nip41.getPrivateKeyAtIndex(mnemonic, 9)
+  // expect(firstKey).toEqual(
+  //   '8495ba55f56485d378aa275604a45e76abbcae177e374fa06af5770c3b8e24af'
+  // )
+  const firstPubkey = getPublicKey(firstKey)
+  // expect(firstPubkey).toEqual(
+  //   '35246813a0dd45e74ce22ecdf052cca8ed47759c8f8d412c281dc2755110956f'
+  // )
+
+  // first key is compromised, revoke it
+  let {parentPrivateKey, event} = nip41.buildRevocationEvent(
+    mnemonic,
+    firstPubkey
+  )
+
+  const secondKey = nip41.getPrivateKeyAtIndex(mnemonic, 8)
+  expect(parentPrivateKey).toEqual(secondKey)
+  expect(secondKey).toEqual(
+    '1b311655ef73bed3bbebc83d0cb3eef42c6aff45f944e3a0c263eb6fdf98c617'
+  )
+
+  expect(event).toHaveProperty('kind', 13)
+  expect(event.tags).toHaveLength(2)
+  expect(event.tags[0]).toHaveLength(2)
+  expect(event.tags[1]).toHaveLength(2)
+  expect(event.tags[0][0]).toEqual('p')
+  expect(event.tags[1][0]).toEqual('hidden-key')
+
+  let hiddenKey = secp256k1.utils.hexToBytes(event.tags[1][1])
+
+  let pubkeyAlt1 = secp256k1.utils
+    .bytesToHex(
+      nip41.getChildPublicKey(
+        secp256k1.utils.hexToBytes('02' + event.pubkey),
+        hiddenKey
+      )
+    )
+    .slice(2)
+  let pubkeyAlt2 = secp256k1.utils
+    .bytesToHex(
+      nip41.getChildPublicKey(
+        secp256k1.utils.hexToBytes('03' + event.pubkey),
+        hiddenKey
+      )
+    )
+    .slice(2)
+
+  expect([pubkeyAlt1, pubkeyAlt2]).toContain(event.tags[0][1])
+
+  // receiver of revocation event can validate it
+  let secondPubkey = getPublicKey(secondKey)
+  expect(event.pubkey).toEqual(secondPubkey)
+  expect(validateEvent(event)).toBeTruthy()
+  expect(verifySignature(event)).toBeTruthy()
+  expect(nip41.validateRevocation(event)).toBeTruthy()
+})

nip41.ts

@@ -0,0 +1,160 @@
+import * as secp256k1 from '@noble/secp256k1'
+import {sha256} from '@noble/hashes/sha256'
+import {mnemonicToSeedSync} from '@scure/bip39'
+import {HARDENED_OFFSET, HDKey} from '@scure/bip32'
+
+import {getPublicKey} from './keys'
+import {Event, getEventHash, Kind, signEvent, verifySignature} from './event'
+
+const MaxKeys = 256
+
+function getRootFromMnemonic(mnemonic: string): HDKey {
+  return HDKey.fromMasterSeed(mnemonicToSeedSync(mnemonic)).derive(
+    `m/44'/1237'/41'`
+  )
+}
+
+export function getPrivateKeyAtIndex(
+  mnemonic: string,
+  targetIdx: number
+): string {
+  let root = getRootFromMnemonic(mnemonic)
+  let rootPrivateKey = secp256k1.utils.bytesToHex(root.privateKey as Uint8Array)
+  let currentPrivateKey = rootPrivateKey
+
+  for (let idx = 1; idx <= targetIdx; idx++) {
+    let hiddenPrivateKey = secp256k1.utils.bytesToHex(
+      root.deriveChild(idx + HARDENED_OFFSET).privateKey as Uint8Array
+    )
+    currentPrivateKey = getChildPrivateKey(currentPrivateKey, hiddenPrivateKey)
+  }
+
+  return currentPrivateKey
+}
+
+export function getPublicKeyAtIndex(
+  root: HDKey,
+  targetIdx: number
+): Uint8Array {
+  let rootPublicKey = root.publicKey as Uint8Array
+
+  let currentPublicKey = rootPublicKey
+  for (let idx = 1; idx <= targetIdx; idx++) {
+    let hiddenPublicKey = root.deriveChild(idx + HARDENED_OFFSET)
+      .publicKey as Uint8Array
+    currentPublicKey = getChildPublicKey(currentPublicKey, hiddenPublicKey)
+  }
+
+  return currentPublicKey
+}
+
+function getIndexOfPublicKey(root: HDKey, publicKey: string): number {
+  let rootPublicKey = root.publicKey as Uint8Array
+  if (secp256k1.utils.bytesToHex(rootPublicKey).slice(2) === publicKey) return 0
+
+  let currentPublicKey = rootPublicKey
+  for (let idx = 1; idx <= MaxKeys; idx++) {
+    let hiddenPublicKey = root.deriveChild(idx + HARDENED_OFFSET)
+      .publicKey as Uint8Array
+    let pubkeyAtIndex = getChildPublicKey(currentPublicKey, hiddenPublicKey)
+    if (secp256k1.utils.bytesToHex(pubkeyAtIndex).slice(2) === publicKey)
+      return idx
+
+    currentPublicKey = pubkeyAtIndex
+  }
+
+  throw new Error(
+    `public key ${publicKey} not in the set of the first ${MaxKeys} public keys`
+  )
+}
+
+export function getChildPublicKey(
+  parentPublicKey: Uint8Array,
+  hiddenPublicKey: Uint8Array
+): Uint8Array {
+  if (parentPublicKey.length !== 33 || hiddenPublicKey.length !== 33)
+    throw new Error(
+      'getChildPublicKey() requires public keys with the leading differentiator byte.'
+    )
+
+  let hash = sha256(
+    secp256k1.utils.concatBytes(hiddenPublicKey, parentPublicKey)
+  )
+  let hashPoint = secp256k1.Point.fromPrivateKey(hash)
+  let point = secp256k1.Point.fromHex(hiddenPublicKey).add(hashPoint)
+  return point.toRawBytes(true)
+}
+
+export function getChildPrivateKey(
+  parentPrivateKey: string,
+  hiddenPrivateKey: string
+): string {
+  let parentPublicKey = secp256k1.getPublicKey(parentPrivateKey, true)
+  let hiddenPublicKey = secp256k1.getPublicKey(hiddenPrivateKey, true)
+  let hash = sha256(
+    secp256k1.utils.concatBytes(hiddenPublicKey, parentPublicKey)
+  )
+  let hashScalar = BigInt(`0x${secp256k1.utils.bytesToHex(hash)}`)
+  let hiddenPrivateKeyScalar = BigInt(`0x${hiddenPrivateKey}`)
+  let sumScalar = hiddenPrivateKeyScalar + hashScalar
+  let modulo = secp256k1.utils.mod(sumScalar, secp256k1.CURVE.n)
+  return modulo.toString(16).padStart(64, '0')
+}
+
+export function buildRevocationEvent(
+  mnemonic: string,
+  compromisedKey: string,
+  content = ''
+): {
+  parentPrivateKey: string
+  event: Event
+} {
+  let root = getRootFromMnemonic(mnemonic)
+  let idx = getIndexOfPublicKey(root, compromisedKey)
+  let hiddenKey = secp256k1.utils.bytesToHex(
+    root.deriveChild(idx + HARDENED_OFFSET).publicKey as Uint8Array
+  )
+  let parentPrivateKey = getPrivateKeyAtIndex(mnemonic, idx - 1)
+  let parentPublicKey = getPublicKey(parentPrivateKey)
+
+  let event: Event = {
+    kind: 13,
+    tags: [
+      ['p', compromisedKey],
+      ['hidden-key', hiddenKey]
+    ],
+    created_at: Math.round(Date.now() / 1000),
+    content,
+    pubkey: parentPublicKey
+  }
+
+  event.sig = signEvent(event, parentPrivateKey)
+  event.id = getEventHash(event)
+
+  return {parentPrivateKey, event}
+}
+
+export function validateRevocation(event: Event): boolean {
+  if (event.kind !== Kind.StatelessRevocation) return false
+  if (!verifySignature(event)) return false
+
+  let invalidKeyTag = event.tags.find(([t, v]) => t === 'p' && v)
+  if (!invalidKeyTag) return false
+  let invalidKey = invalidKeyTag[1]
+
+  let hiddenKeyTag = event.tags.find(([t, v]) => t === 'hidden-key' && v)
+  if (!hiddenKeyTag) return false
+  let hiddenKey = secp256k1.utils.hexToBytes(hiddenKeyTag[1])
+  if (hiddenKey.length !== 33) return false
+
+  let currentKeyAlt1 = secp256k1.utils.hexToBytes('02' + event.pubkey)
+  let currentKeyAlt2 = secp256k1.utils.hexToBytes('03' + event.pubkey)
+  let childKeyAlt1 = secp256k1.utils
+    .bytesToHex(getChildPublicKey(currentKeyAlt1, hiddenKey))
+    .slice(2)
+  let childKeyAlt2 = secp256k1.utils
+    .bytesToHex(getChildPublicKey(currentKeyAlt2, hiddenKey))
+    .slice(2)
+
+  return childKeyAlt1 === invalidKey || childKeyAlt2 === invalidKey
+}