IMPLEMENT X3DH (without OMEMO)
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107
lib/src/x3dh/x3dh.dart
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107
lib/src/x3dh/x3dh.dart
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@ -0,0 +1,107 @@
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import 'dart:convert';
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import 'package:cryptography/cryptography.dart';
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import 'package:cryptography/dart.dart';
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/// The overarching assumption is that we use Ed25519 keys for the identity keys
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class X3DHRun {
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const X3DHRun(this.epk, this.sharedSecret);
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final SimpleKeyPair epk;
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final List<int> sharedSecret;
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}
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SimpleKeyPairData fromPublicKey(SimplePublicKey pk) {
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return SimpleKeyPairData([], publicKey: pk, type: KeyPairType.x25519);
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}
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Future<List<int>> sig(SimpleKeyPair keyPair, List<int> message) async {
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final signature = await Ed25519().sign(
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message,
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keyPair: keyPair,
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);
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return signature.bytes;
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}
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/// Performs X25519 with [pk1] and [pk2]. If [identityKey] is set, then
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/// it indicates which of [pk1] ([identityKey] == 1) or [pk2] ([identityKey] == 2)
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/// is the identity key.
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Future<List<int>> dh(SimpleKeyPair kp, SimplePublicKey pk, int identityKey) async {
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var ckp = kp;
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var cpk = pk;
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/*
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if (identityKey == 1) {
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final pkc = await DartEd25519.publicKeyToCurve25519(kp);
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final skc = await DartEd25519.privateKeyToCurve25519(kp);
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ckp = SimpleKeyPairData(skc, publicKey: pkc, type: KeyPairType.x25519);
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} else if (identityKey == 2) {
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cpk = await DartEd25519.publicKeyToCurve25519(fromPublicKey(pk));
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}
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*/
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final shared = await Cryptography.instance.x25519().sharedSecretKey(
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keyPair: ckp,
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remotePublicKey: cpk,
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);
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return shared.extractBytes();
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}
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Future<List<int>> kdf(List<int> km) async {
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final f = List<int>.filled(32, 0xFF);
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final input = List<int>.empty(growable: true);
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input
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..addAll(f)
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..addAll(km);
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final algorithm = Hkdf(
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hmac: Hmac(Sha256()),
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outputLength: 32,
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);
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final output = await algorithm.deriveKey(
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secretKey: SecretKey(input),
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// TODO: Fix
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nonce: List<int>.filled(32, 0x00),
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info: utf8.encode('OMEMO X3DH'),
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);
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return output.extractBytes();
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}
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List<int> concat(List<List<int>> inputs) {
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final tmp = List<int>.empty(growable: true);
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for (final input in inputs) {
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tmp.addAll(input);
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}
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return tmp;
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}
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// Alice -> Bob
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Future<X3DHRun> x3dhFromPrekeyBundle(SimplePublicKey ikb, SimplePublicKey spkb, SimplePublicKey opkb, SimpleKeyPair ika) async {
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// Generate EPK
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final epk = await Cryptography.instance.x25519().newKeyPair();
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final dh1 = await dh(ika, spkb, 1);
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final dh2 = await dh(epk, ikb, 2);
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final dh3 = await dh(epk, spkb, 0);
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final dh4 = await dh(epk, opkb, 0);
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final sk = await kdf(concat([dh1, dh2, dh3, dh4]));
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return X3DHRun(
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epk,
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sk,
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);
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}
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Future<List<int>> x3dhFromInitialMessage(SimplePublicKey ika, SimplePublicKey epk, SimpleKeyPair opkb, SimpleKeyPair spk, SimpleKeyPair ikb) async {
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final dh1 = await dh(spk, ika, 2);
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final dh2 = await dh(ikb, epk, 1);
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final dh3 = await dh(spk, epk, 0);
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final dh4 = await dh(opkb, epk, 0);
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return kdf(concat([dh1, dh2, dh3, dh4]));
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}
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11
pubspec.yaml
11
pubspec.yaml
@ -1,14 +1,15 @@
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name: omemo_dart
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description: A starting point for Dart libraries or applications.
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version: 1.0.0
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# homepage: https://www.example.com
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description: An XMPP library independent OMEMO library
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version: 0.1.0
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environment:
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sdk: '>=2.15.1 <3.0.0'
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# dependencies:
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# path: ^1.8.0
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dependencies:
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cryptography:
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path: ../cryptography/cryptography
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pinenacl:
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dev_dependencies:
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lints: ^1.0.0
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@ -1,16 +1,61 @@
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import 'package:omemo_dart/omemo_dart.dart';
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import 'package:cryptography/cryptography.dart';
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import 'package:cryptography/dart.dart';
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import 'package:test/test.dart';
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import 'package:omemo_dart/src/x3dh/x3dh.dart';
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Future<List<int>> publicKeyBytes(SimpleKeyPair kp) async {
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final pk = await kp.extractPublicKey();
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return pk.bytes;
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}
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Future<SimplePublicKey> publicKey(SimpleKeyPair kp) async {
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//return await DartEd25519.publicKeyToCurve25519(kp);
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return kp.extractPublicKey();
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}
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Future<SimpleKeyPair> toCurve(SimpleKeyPair kp) async {
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//final pk = await DartEd25519.publicKeyToCurve25519(kp);
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//final sk = await DartEd25519.privateKeyToCurve25519(kp);
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//return SimpleKeyPairData(sk, publicKey: pk, type: KeyPairType.x25519);
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return kp;
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}
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void main() {
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group('A group of tests', () {
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final awesome = Awesome();
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test("X3DH", () async {
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final ed = Ed25519();
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final x = Cryptography.instance.x25519();
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setUp(() {
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// Additional setup goes here.
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});
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// Generate IKs for Alice and Bob
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final ikAlice = await x.newKeyPair();
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final ikBob = await x.newKeyPair();
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test('First Test', () {
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expect(awesome.isAwesome, isTrue);
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});
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// Generate SPKs for Alice and Bob
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final spkAlice = await x.newKeyPair();
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final spkSigAlice = await sig(ikAlice, await publicKeyBytes(spkAlice));
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final spkBob = await x.newKeyPair();
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final spkSigBob = await sig(ikBob, await publicKeyBytes(spkBob));
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// Generate an OPK for Alice and Bob
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final opkAlice = await x.newKeyPair();
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final opkBob = await x.newKeyPair();
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// Perform X3DH
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final aliceMessage = await x3dhFromPrekeyBundle(
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await ikBob.extractPublicKey(),
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await spkBob.extractPublicKey(),
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await opkBob.extractPublicKey(),
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ikAlice,
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);
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final bobDh = await x3dhFromInitialMessage(
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await ikAlice.extractPublicKey(),
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await aliceMessage.epk.extractPublicKey(),
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opkBob,
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spkBob,
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ikBob,
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);
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expect(aliceMessage.sharedSecret, bobDh);
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});
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}
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