docs: Migrate the example to the "new" OmemoManager

Fixes #30.

.github/FUNDING.yml

@@ -0,0 +1 @@
+ko_fi: papatutuwawa

.gitignore

@@ -12,6 +12,3 @@ pubspec.lock
 # NixOS
 .direnv
 .envrc
-
-# Protobuf build artifacts
-lib/protobuf/*.dart

.pubignore

@@ -0,0 +1 @@
+lib/protobuf

.woodpecker.yml

@@ -0,0 +1,11 @@
+pipeline:
+  lint:
+    image: dart:2.18.1
+    commands:
+      - dart pub get
+      - dart analyze --fatal-infos --fatal-warnings
+  test:
+    image: dart:2.18.1
+    commands:
+      - dart pub get
+      - dart test

CHANGELOG.md

@@ -9,9 +9,48 @@
 
 - Fix bug with the Double Ratchet causing only the initial message to be decryptable
 - Expose `getDeviceMap` as a developer usable function
-
 ## 0.2.0
 
 - Add convenience functions `getDeviceId` and `getDeviceBundle`
 - Creating a new ratchet with an id for which we already have a ratchet will now overwrite the old ratchet
 - Ratchet now carry an "acknowledged" attribute
+
+## 0.2.1
+
+- Add `isRatchetAcknowledged`
+- Ratchets that are created due to accepting a kex are now unacknowledged
+
+## 0.3.0
+
+- Implement enabling and disabling ratchets via the TrustManager interface
+- Fix deserialization of the various objects
+- Remove the BTBV TrustManager's loadState method. Just use the constructor
+- Allow removing all ratchets for a given Jid
+- If an error occurs while decrypting the message, the ratchet will now be reset to its prior state
+- Fix a bug within the Varint encoding function. This should fix some occasional UnknownSignedPrekeyExceptions
+- Remove OmemoSessionManager's toJson and fromJson. Use toJsonWithoutSessions and fromJsonWithoutSessions. Restoring sessions is not out-of-scope for that function
+
+## 0.3.1
+
+- Fix a bug that caused the device's id to change when replacing a OPK
+- Every decryption failure now causes the ratchet to be restored to a pre-decryption state
+- Add method to get the device's fingerprint
+
+## 0.4.0
+
+- Deprecate `OmemoSessionManager`. Use `OmemoManager` instead.
+- Implement queued access to the ratchets inside the `OmemoManager`.
+- Implement heartbeat messages.
+- [BREAKING] Rename `Device` to `OmemoDevice`.
+
+## 0.4.1
+
+- Fix fetching the current device and building a ratchet session with it when encrypting for our own JID
+
+## 0.4.2
+
+- Fix removeAllRatchets not removing, well, all ratchets. In fact, it did not remove any ratchet.
+
+## 0.4.3
+
+- Fix bug that causes ratchets to be unable to decrypt anything after receiving a heartbeat with a completely new session

README.md

@@ -28,7 +28,7 @@ Include `omemo_dart` in your `pubspec.yaml` like this:
 dependencies:
   omemo_dart:
     hosted: https://git.polynom.me/api/packages/PapaTutuWawa/pub
-    version: ^0.1.0
+    version: ^0.4.3
   # [...]
 
 # [...]
@@ -56,3 +56,9 @@ messages' formatting.
 Licensed under the MIT license.
 
 See `LICENSE`.
+
+## Support
+
+If you like what I do and you want to support me, feel free to donate to me on Ko-Fi.
+
+[<img src="https://codeberg.org/moxxy/moxxyv2/raw/branch/master/assets/repo/kofi.png" height="36" style="height: 36px; border: 0px;"></img>](https://ko-fi.com/papatutuwawa)

analysis_options.yaml

@@ -10,3 +10,7 @@ linter:
 analyzer:
   exclude:
     - "lib/protobuf/*.dart"
+    # TODO: Remove once OmemoSessionManager is gone
+    - "test/omemo_test.dart"
+    - "example/omemo_dart_example.dart"
+    - "test/serialisation_test.dart"

example/omemo_dart_example.dart

@@ -8,28 +8,45 @@ void main() async {
   const aliceJid = 'alice@some.server';
   const bobJid = 'bob@other.serve';
 
-  // You are Alice and want to begin using OMEMO, so you first create a SessionManager
+  // You are Alice and want to begin using OMEMO, so you first create an OmemoManager.
-  final aliceSession = await OmemoSessionManager.generateNewIdentity(
+  final aliceManager = OmemoManager(
-    // The bare Jid of Alice as a String
+    // Generate Alice's OMEMO device bundle. We can specify how many One-time Prekeys we want, but
-    aliceJid,
+    // per default, omemo_dart generates 100 (recommended by XEP-0384).
+    await OmemoDevice.generateNewDevice(aliceJid),
     // The trust manager we want to use. In this case, we use the provided one that
     // implements "Blind Trust Before Verification". To make things simpler, we keep
     // no persistent data and can thus use the MemoryBTBVTrustManager. If we wanted to keep
     // the state, we would have to override BlindTrustBeforeVerificationTrustManager.
     MemoryBTBVTrustManager(),
-    // Here we specify how many Onetime Prekeys we want to have. XEP-0384 recommends around
+    // This function is called whenever we need to send an OMEMO heartbeat to [recipient].
-    // 100 OPKs, so let's generate 100. The parameter defaults to 100.
+    // [result] is the encryted data to include. This needs to be wired into your XMPP library's
-    //opkAmount: 100,
+    // OMEMO implementation.
+    // For simplicity, we use an empty function and imagine it works.
+    (result, recipient) async => {},
+    // This function is called whenever we need to fetch the device list for [jid].
+    // This needs to be wired into your XMPP library's OMEMO implementation.
+    // For simplicity, we use an empty function and imagine it works.
+    (jid) async => [],
+    // This function is called whenever we need to fetch the device bundle with id [id] from [jid].
+    // This needs to be wired into your XMPP library's OMEMO implementation.
+    // For simplicity, we use an empty function and imagine it works.
+    (jid, id) async => null,
+    // This function is called whenever we need to subscribe to [jid]'s device list PubSub node.
+    // This needs to be wired into your XMPP library's OMEMO implementation.
+    // For simplicity, we use an empty function and imagine it works.
+    (jid) async {},
   );
 
   // Alice now wants to chat with Bob at his bare Jid "bob@other.server". To make things
   // simple, we just generate the identity bundle ourselves. In the real world, we would
   // request it using PEP and then convert the device bundle into a OmemoBundle object.
-  final bobSession = await OmemoSessionManager.generateNewIdentity(
+  final bobManager = OmemoManager(
-    bobJid,
+    await OmemoDevice.generateNewDevice(bobJid),
     MemoryBTBVTrustManager(),
-    // Just for illustrative purposes
+    (result, recipient) async => {},
-    opkAmount: 1,
+    (jid) async => [],
+    (jid, id) async => null,
+    (jid) async {},
   );
 
   // Alice prepares to send the message to Bob, so she builds the message stanza and
@@ -56,19 +73,18 @@ void main() async {
 
   // Since Alice has no open session with Bob, we need to tell the session manager to build
   // it when sending the message.
-  final message = await aliceSession.encryptToJid(
+  final message = await aliceSession.onOutgoingStanza(
+    OmemoOutgoingStanza(
       // The bare receiver Jid
-    bobJid,
+      [bobJid],
-    // The envelope we want to encrypt
+
+      // The payload we want to encrypt, i.e. the envelope.
       envelope,
-    // Since this is the first time Alice contacts Bob from this device, we need to create
+    ),
-    // a new session. Let's also assume that Bob only has one device. We may, however,
-    // add more bundles to newSessions, if we know of more.
-    newSessions: [
-      await bobSession.getDeviceBundle(),
-    ],
   );
 
+  // In a proper implementation, we should also do some error checking here.
+
   // Alice now builds the actual message stanza for Bob
   final payload = base64.encode(message.ciphertext!);
   final aliceDevice = await aliceSession.getDevice();
@@ -110,15 +126,26 @@ void main() async {
 
   // Bob extracts the payload and attempts to decrypt it.
   // ignore: unused_local_variable
-  final bobMessage = await bobSession.decryptMessage(
+  final bobMessage = await bobManager.onIncomingStanza(
-    // base64 decode the payload
+    OmemoIncomingStanza(
-    base64.decode(payload),
+      // The bare sender JID of the message. In this case, it's Alice's.
-    // Specify the Jid of the sender
       aliceJid,
-    // Specify the device identifier of the sender (the "sid" attribute of <header />)
+
+      // The 'sid' attribute of the <header /> element. Here, we know that Alice only has one device.
       aliceDevice.id,
-    // The deserialised keys
+
+      // Time the message was sent. Since the message was not delayed, we use the
+      // current time.
+      DateTime.now().millisecondsSinceEpoch,
+
+      /// The decoded <key /> elements. from the header. Note that we only include the ones
+      /// relevant for Bob, so all children of <keys jid='$bobJid' />.
       keys,
+
+      /// The text of the <payload /> element, if it exists. If not, then the message might be
+      /// a hearbeat, where no payload is sent. In that case, use null.
+      payload,
+    ),
   );
 
   // All Bob has to do now is replace the OMEMO wrapper element

lib/omemo_dart.dart

@@ -10,8 +10,9 @@ export 'src/omemo/encrypted_key.dart';
 export 'src/omemo/encryption_result.dart';
 export 'src/omemo/events.dart';
 export 'src/omemo/fingerprint.dart';
+export 'src/omemo/omemomanager.dart';
 export 'src/omemo/ratchet_map_key.dart';
-export 'src/omemo/sessionmanager.dart';
+export 'src/omemo/stanza.dart';
 export 'src/trust/base.dart';
 export 'src/trust/btbv.dart';
 export 'src/x3dh/x3dh.dart';

lib/protobuf/schema.pb.dart

@@ -0,0 +1,379 @@
+///
+//  Generated code. Do not modify.
+//  source: schema.proto
+//
+// @dart = 2.12
+// ignore_for_file: annotate_overrides,camel_case_types,constant_identifier_names,directives_ordering,library_prefixes,non_constant_identifier_names,prefer_final_fields,return_of_invalid_type,unnecessary_const,unnecessary_import,unnecessary_this,unused_import,unused_shown_name
+
+import 'dart:core' as $core;
+
+import 'package:protobuf/protobuf.dart' as $pb;
+
+class OMEMOMessage extends $pb.GeneratedMessage {
+  static final $pb.BuilderInfo _i = $pb.BuilderInfo(
+      const $core.bool.fromEnvironment('protobuf.omit_message_names')
+          ? ''
+          : 'OMEMOMessage',
+      createEmptyInstance: create)
+    ..a<$core.int>(
+        1,
+        const $core.bool.fromEnvironment('protobuf.omit_field_names')
+            ? ''
+            : 'n',
+        $pb.PbFieldType.QU3)
+    ..a<$core.int>(
+        2,
+        const $core.bool.fromEnvironment('protobuf.omit_field_names')
+            ? ''
+            : 'pn',
+        $pb.PbFieldType.QU3)
+    ..a<$core.List<$core.int>>(
+        3,
+        const $core.bool.fromEnvironment('protobuf.omit_field_names')
+            ? ''
+            : 'dhPub',
+        $pb.PbFieldType.QY)
+    ..a<$core.List<$core.int>>(
+        4,
+        const $core.bool.fromEnvironment('protobuf.omit_field_names')
+            ? ''
+            : 'ciphertext',
+        $pb.PbFieldType.OY);
+
+  OMEMOMessage._() : super();
+  factory OMEMOMessage({
+    $core.int? n,
+    $core.int? pn,
+    $core.List<$core.int>? dhPub,
+    $core.List<$core.int>? ciphertext,
+  }) {
+    final _result = create();
+    if (n != null) {
+      _result.n = n;
+    }
+    if (pn != null) {
+      _result.pn = pn;
+    }
+    if (dhPub != null) {
+      _result.dhPub = dhPub;
+    }
+    if (ciphertext != null) {
+      _result.ciphertext = ciphertext;
+    }
+    return _result;
+  }
+  factory OMEMOMessage.fromBuffer($core.List<$core.int> i,
+          [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
+      create()..mergeFromBuffer(i, r);
+  factory OMEMOMessage.fromJson($core.String i,
+          [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
+      create()..mergeFromJson(i, r);
+  @$core.Deprecated('Using this can add significant overhead to your binary. '
+      'Use [GeneratedMessageGenericExtensions.deepCopy] instead. '
+      'Will be removed in next major version')
+  OMEMOMessage clone() => OMEMOMessage()..mergeFromMessage(this);
+  @$core.Deprecated('Using this can add significant overhead to your binary. '
+      'Use [GeneratedMessageGenericExtensions.rebuild] instead. '
+      'Will be removed in next major version')
+  OMEMOMessage copyWith(void Function(OMEMOMessage) updates) =>
+      super.copyWith((message) => updates(message as OMEMOMessage))
+          as OMEMOMessage; // ignore: deprecated_member_use
+  $pb.BuilderInfo get info_ => _i;
+  @$core.pragma('dart2js:noInline')
+  static OMEMOMessage create() => OMEMOMessage._();
+  OMEMOMessage createEmptyInstance() => create();
+  static $pb.PbList<OMEMOMessage> createRepeated() =>
+      $pb.PbList<OMEMOMessage>();
+  @$core.pragma('dart2js:noInline')
+  static OMEMOMessage getDefault() => _defaultInstance ??=
+      $pb.GeneratedMessage.$_defaultFor<OMEMOMessage>(create);
+  static OMEMOMessage? _defaultInstance;
+
+  @$pb.TagNumber(1)
+  $core.int get n => $_getIZ(0);
+  @$pb.TagNumber(1)
+  set n($core.int v) {
+    $_setUnsignedInt32(0, v);
+  }
+
+  @$pb.TagNumber(1)
+  $core.bool hasN() => $_has(0);
+  @$pb.TagNumber(1)
+  void clearN() => clearField(1);
+
+  @$pb.TagNumber(2)
+  $core.int get pn => $_getIZ(1);
+  @$pb.TagNumber(2)
+  set pn($core.int v) {
+    $_setUnsignedInt32(1, v);
+  }
+
+  @$pb.TagNumber(2)
+  $core.bool hasPn() => $_has(1);
+  @$pb.TagNumber(2)
+  void clearPn() => clearField(2);
+
+  @$pb.TagNumber(3)
+  $core.List<$core.int> get dhPub => $_getN(2);
+  @$pb.TagNumber(3)
+  set dhPub($core.List<$core.int> v) {
+    $_setBytes(2, v);
+  }
+
+  @$pb.TagNumber(3)
+  $core.bool hasDhPub() => $_has(2);
+  @$pb.TagNumber(3)
+  void clearDhPub() => clearField(3);
+
+  @$pb.TagNumber(4)
+  $core.List<$core.int> get ciphertext => $_getN(3);
+  @$pb.TagNumber(4)
+  set ciphertext($core.List<$core.int> v) {
+    $_setBytes(3, v);
+  }
+
+  @$pb.TagNumber(4)
+  $core.bool hasCiphertext() => $_has(3);
+  @$pb.TagNumber(4)
+  void clearCiphertext() => clearField(4);
+}
+
+class OMEMOAuthenticatedMessage extends $pb.GeneratedMessage {
+  static final $pb.BuilderInfo _i = $pb.BuilderInfo(
+      const $core.bool.fromEnvironment('protobuf.omit_message_names')
+          ? ''
+          : 'OMEMOAuthenticatedMessage',
+      createEmptyInstance: create)
+    ..a<$core.List<$core.int>>(
+        1,
+        const $core.bool.fromEnvironment('protobuf.omit_field_names')
+            ? ''
+            : 'mac',
+        $pb.PbFieldType.QY)
+    ..a<$core.List<$core.int>>(
+        2,
+        const $core.bool.fromEnvironment('protobuf.omit_field_names')
+            ? ''
+            : 'message',
+        $pb.PbFieldType.QY);
+
+  OMEMOAuthenticatedMessage._() : super();
+  factory OMEMOAuthenticatedMessage({
+    $core.List<$core.int>? mac,
+    $core.List<$core.int>? message,
+  }) {
+    final _result = create();
+    if (mac != null) {
+      _result.mac = mac;
+    }
+    if (message != null) {
+      _result.message = message;
+    }
+    return _result;
+  }
+  factory OMEMOAuthenticatedMessage.fromBuffer($core.List<$core.int> i,
+          [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
+      create()..mergeFromBuffer(i, r);
+  factory OMEMOAuthenticatedMessage.fromJson($core.String i,
+          [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
+      create()..mergeFromJson(i, r);
+  @$core.Deprecated('Using this can add significant overhead to your binary. '
+      'Use [GeneratedMessageGenericExtensions.deepCopy] instead. '
+      'Will be removed in next major version')
+  OMEMOAuthenticatedMessage clone() =>
+      OMEMOAuthenticatedMessage()..mergeFromMessage(this);
+  @$core.Deprecated('Using this can add significant overhead to your binary. '
+      'Use [GeneratedMessageGenericExtensions.rebuild] instead. '
+      'Will be removed in next major version')
+  OMEMOAuthenticatedMessage copyWith(
+          void Function(OMEMOAuthenticatedMessage) updates) =>
+      super.copyWith((message) => updates(message as OMEMOAuthenticatedMessage))
+          as OMEMOAuthenticatedMessage; // ignore: deprecated_member_use
+  $pb.BuilderInfo get info_ => _i;
+  @$core.pragma('dart2js:noInline')
+  static OMEMOAuthenticatedMessage create() => OMEMOAuthenticatedMessage._();
+  OMEMOAuthenticatedMessage createEmptyInstance() => create();
+  static $pb.PbList<OMEMOAuthenticatedMessage> createRepeated() =>
+      $pb.PbList<OMEMOAuthenticatedMessage>();
+  @$core.pragma('dart2js:noInline')
+  static OMEMOAuthenticatedMessage getDefault() => _defaultInstance ??=
+      $pb.GeneratedMessage.$_defaultFor<OMEMOAuthenticatedMessage>(create);
+  static OMEMOAuthenticatedMessage? _defaultInstance;
+
+  @$pb.TagNumber(1)
+  $core.List<$core.int> get mac => $_getN(0);
+  @$pb.TagNumber(1)
+  set mac($core.List<$core.int> v) {
+    $_setBytes(0, v);
+  }
+
+  @$pb.TagNumber(1)
+  $core.bool hasMac() => $_has(0);
+  @$pb.TagNumber(1)
+  void clearMac() => clearField(1);
+
+  @$pb.TagNumber(2)
+  $core.List<$core.int> get message => $_getN(1);
+  @$pb.TagNumber(2)
+  set message($core.List<$core.int> v) {
+    $_setBytes(1, v);
+  }
+
+  @$pb.TagNumber(2)
+  $core.bool hasMessage() => $_has(1);
+  @$pb.TagNumber(2)
+  void clearMessage() => clearField(2);
+}
+
+class OMEMOKeyExchange extends $pb.GeneratedMessage {
+  static final $pb.BuilderInfo _i = $pb.BuilderInfo(
+      const $core.bool.fromEnvironment('protobuf.omit_message_names')
+          ? ''
+          : 'OMEMOKeyExchange',
+      createEmptyInstance: create)
+    ..a<$core.int>(
+        1,
+        const $core.bool.fromEnvironment('protobuf.omit_field_names')
+            ? ''
+            : 'pkId',
+        $pb.PbFieldType.QU3)
+    ..a<$core.int>(
+        2,
+        const $core.bool.fromEnvironment('protobuf.omit_field_names')
+            ? ''
+            : 'spkId',
+        $pb.PbFieldType.QU3)
+    ..a<$core.List<$core.int>>(
+        3,
+        const $core.bool.fromEnvironment('protobuf.omit_field_names')
+            ? ''
+            : 'ik',
+        $pb.PbFieldType.QY)
+    ..a<$core.List<$core.int>>(
+        4,
+        const $core.bool.fromEnvironment('protobuf.omit_field_names')
+            ? ''
+            : 'ek',
+        $pb.PbFieldType.QY)
+    ..aQM<OMEMOAuthenticatedMessage>(
+        5,
+        const $core.bool.fromEnvironment('protobuf.omit_field_names')
+            ? ''
+            : 'message',
+        subBuilder: OMEMOAuthenticatedMessage.create);
+
+  OMEMOKeyExchange._() : super();
+  factory OMEMOKeyExchange({
+    $core.int? pkId,
+    $core.int? spkId,
+    $core.List<$core.int>? ik,
+    $core.List<$core.int>? ek,
+    OMEMOAuthenticatedMessage? message,
+  }) {
+    final _result = create();
+    if (pkId != null) {
+      _result.pkId = pkId;
+    }
+    if (spkId != null) {
+      _result.spkId = spkId;
+    }
+    if (ik != null) {
+      _result.ik = ik;
+    }
+    if (ek != null) {
+      _result.ek = ek;
+    }
+    if (message != null) {
+      _result.message = message;
+    }
+    return _result;
+  }
+  factory OMEMOKeyExchange.fromBuffer($core.List<$core.int> i,
+          [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
+      create()..mergeFromBuffer(i, r);
+  factory OMEMOKeyExchange.fromJson($core.String i,
+          [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) =>
+      create()..mergeFromJson(i, r);
+  @$core.Deprecated('Using this can add significant overhead to your binary. '
+      'Use [GeneratedMessageGenericExtensions.deepCopy] instead. '
+      'Will be removed in next major version')
+  OMEMOKeyExchange clone() => OMEMOKeyExchange()..mergeFromMessage(this);
+  @$core.Deprecated('Using this can add significant overhead to your binary. '
+      'Use [GeneratedMessageGenericExtensions.rebuild] instead. '
+      'Will be removed in next major version')
+  OMEMOKeyExchange copyWith(void Function(OMEMOKeyExchange) updates) =>
+      super.copyWith((message) => updates(message as OMEMOKeyExchange))
+          as OMEMOKeyExchange; // ignore: deprecated_member_use
+  $pb.BuilderInfo get info_ => _i;
+  @$core.pragma('dart2js:noInline')
+  static OMEMOKeyExchange create() => OMEMOKeyExchange._();
+  OMEMOKeyExchange createEmptyInstance() => create();
+  static $pb.PbList<OMEMOKeyExchange> createRepeated() =>
+      $pb.PbList<OMEMOKeyExchange>();
+  @$core.pragma('dart2js:noInline')
+  static OMEMOKeyExchange getDefault() => _defaultInstance ??=
+      $pb.GeneratedMessage.$_defaultFor<OMEMOKeyExchange>(create);
+  static OMEMOKeyExchange? _defaultInstance;
+
+  @$pb.TagNumber(1)
+  $core.int get pkId => $_getIZ(0);
+  @$pb.TagNumber(1)
+  set pkId($core.int v) {
+    $_setUnsignedInt32(0, v);
+  }
+
+  @$pb.TagNumber(1)
+  $core.bool hasPkId() => $_has(0);
+  @$pb.TagNumber(1)
+  void clearPkId() => clearField(1);
+
+  @$pb.TagNumber(2)
+  $core.int get spkId => $_getIZ(1);
+  @$pb.TagNumber(2)
+  set spkId($core.int v) {
+    $_setUnsignedInt32(1, v);
+  }
+
+  @$pb.TagNumber(2)
+  $core.bool hasSpkId() => $_has(1);
+  @$pb.TagNumber(2)
+  void clearSpkId() => clearField(2);
+
+  @$pb.TagNumber(3)
+  $core.List<$core.int> get ik => $_getN(2);
+  @$pb.TagNumber(3)
+  set ik($core.List<$core.int> v) {
+    $_setBytes(2, v);
+  }
+
+  @$pb.TagNumber(3)
+  $core.bool hasIk() => $_has(2);
+  @$pb.TagNumber(3)
+  void clearIk() => clearField(3);
+
+  @$pb.TagNumber(4)
+  $core.List<$core.int> get ek => $_getN(3);
+  @$pb.TagNumber(4)
+  set ek($core.List<$core.int> v) {
+    $_setBytes(3, v);
+  }
+
+  @$pb.TagNumber(4)
+  $core.bool hasEk() => $_has(3);
+  @$pb.TagNumber(4)
+  void clearEk() => clearField(4);
+
+  @$pb.TagNumber(5)
+  OMEMOAuthenticatedMessage get message => $_getN(4);
+  @$pb.TagNumber(5)
+  set message(OMEMOAuthenticatedMessage v) {
+    setField(5, v);
+  }
+
+  @$pb.TagNumber(5)
+  $core.bool hasMessage() => $_has(4);
+  @$pb.TagNumber(5)
+  void clearMessage() => clearField(5);
+  @$pb.TagNumber(5)
+  OMEMOAuthenticatedMessage ensureMessage() => $_ensure(4);
+}

lib/protobuf/schema.pbenum.dart

@@ -0,0 +1,6 @@
+///
+//  Generated code. Do not modify.
+//  source: schema.proto
+//
+// @dart = 2.12
+// ignore_for_file: annotate_overrides,camel_case_types,constant_identifier_names,directives_ordering,library_prefixes,non_constant_identifier_names,prefer_final_fields,return_of_invalid_type,unnecessary_const,unnecessary_import,unnecessary_this,unused_import,unused_shown_name

lib/protobuf/schema.pbjson.dart

@@ -0,0 +1,60 @@
+///
+//  Generated code. Do not modify.
+//  source: schema.proto
+//
+// @dart = 2.12
+// ignore_for_file: annotate_overrides,camel_case_types,constant_identifier_names,deprecated_member_use_from_same_package,directives_ordering,library_prefixes,non_constant_identifier_names,prefer_final_fields,return_of_invalid_type,unnecessary_const,unnecessary_import,unnecessary_this,unused_import,unused_shown_name
+
+import 'dart:core' as $core;
+import 'dart:convert' as $convert;
+import 'dart:typed_data' as $typed_data;
+
+@$core.Deprecated('Use oMEMOMessageDescriptor instead')
+const OMEMOMessage$json = {
+  '1': 'OMEMOMessage',
+  '2': [
+    {'1': 'n', '3': 1, '4': 2, '5': 13, '10': 'n'},
+    {'1': 'pn', '3': 2, '4': 2, '5': 13, '10': 'pn'},
+    {'1': 'dh_pub', '3': 3, '4': 2, '5': 12, '10': 'dhPub'},
+    {'1': 'ciphertext', '3': 4, '4': 1, '5': 12, '10': 'ciphertext'},
+  ],
+};
+
+/// Descriptor for `OMEMOMessage`. Decode as a `google.protobuf.DescriptorProto`.
+final $typed_data.Uint8List oMEMOMessageDescriptor = $convert.base64Decode(
+    'CgxPTUVNT01lc3NhZ2USDAoBbhgBIAIoDVIBbhIOCgJwbhgCIAIoDVICcG4SFQoGZGhfcHViGAMgAigMUgVkaFB1YhIeCgpjaXBoZXJ0ZXh0GAQgASgMUgpjaXBoZXJ0ZXh0');
+@$core.Deprecated('Use oMEMOAuthenticatedMessageDescriptor instead')
+const OMEMOAuthenticatedMessage$json = {
+  '1': 'OMEMOAuthenticatedMessage',
+  '2': [
+    {'1': 'mac', '3': 1, '4': 2, '5': 12, '10': 'mac'},
+    {'1': 'message', '3': 2, '4': 2, '5': 12, '10': 'message'},
+  ],
+};
+
+/// Descriptor for `OMEMOAuthenticatedMessage`. Decode as a `google.protobuf.DescriptorProto`.
+final $typed_data.Uint8List oMEMOAuthenticatedMessageDescriptor =
+    $convert.base64Decode(
+        'ChlPTUVNT0F1dGhlbnRpY2F0ZWRNZXNzYWdlEhAKA21hYxgBIAIoDFIDbWFjEhgKB21lc3NhZ2UYAiACKAxSB21lc3NhZ2U=');
+@$core.Deprecated('Use oMEMOKeyExchangeDescriptor instead')
+const OMEMOKeyExchange$json = {
+  '1': 'OMEMOKeyExchange',
+  '2': [
+    {'1': 'pk_id', '3': 1, '4': 2, '5': 13, '10': 'pkId'},
+    {'1': 'spk_id', '3': 2, '4': 2, '5': 13, '10': 'spkId'},
+    {'1': 'ik', '3': 3, '4': 2, '5': 12, '10': 'ik'},
+    {'1': 'ek', '3': 4, '4': 2, '5': 12, '10': 'ek'},
+    {
+      '1': 'message',
+      '3': 5,
+      '4': 2,
+      '5': 11,
+      '6': '.OMEMOAuthenticatedMessage',
+      '10': 'message'
+    },
+  ],
+};
+
+/// Descriptor for `OMEMOKeyExchange`. Decode as a `google.protobuf.DescriptorProto`.
+final $typed_data.Uint8List oMEMOKeyExchangeDescriptor = $convert.base64Decode(
+    'ChBPTUVNT0tleUV4Y2hhbmdlEhMKBXBrX2lkGAEgAigNUgRwa0lkEhUKBnNwa19pZBgCIAIoDVIFc3BrSWQSDgoCaWsYAyACKAxSAmlrEg4KAmVrGAQgAigMUgJlaxI0CgdtZXNzYWdlGAUgAigLMhouT01FTU9BdXRoZW50aWNhdGVkTWVzc2FnZVIHbWVzc2FnZQ==');

lib/protobuf/schema.pbserver.dart

@@ -0,0 +1,8 @@
+///
+//  Generated code. Do not modify.
+//  source: schema.proto
+//
+// @dart = 2.12
+// ignore_for_file: annotate_overrides,camel_case_types,constant_identifier_names,deprecated_member_use_from_same_package,directives_ordering,library_prefixes,non_constant_identifier_names,prefer_final_fields,return_of_invalid_type,unnecessary_const,unnecessary_import,unnecessary_this,unused_import,unused_shown_name
+
+export 'schema.pb.dart';

lib/src/crypto.dart

@@ -6,7 +6,11 @@ import 'package:omemo_dart/src/keys.dart';
 /// it indicates which of [kp] ([identityKey] == 1) or [pk] ([identityKey] == 2)
 /// is the identity key. This is needed since the identity key pair/public key is
 /// an Ed25519 key, but we need them as X25519 keys for DH.
-Future<List<int>> omemoDH(OmemoKeyPair kp, OmemoPublicKey pk, int identityKey) async {
+Future<List<int>> omemoDH(
+  OmemoKeyPair kp,
+  OmemoPublicKey pk,
+  int identityKey,
+) async {
   var ckp = kp;
   var cpk = pk;
 
@@ -25,7 +29,6 @@ Future<List<int>> omemoDH(OmemoKeyPair kp, OmemoPublicKey pk, int identityKey) a
 }
 
 class HkdfKeyResult {
-
   const HkdfKeyResult(this.encryptionKey, this.authenticationKey, this.iv);
   final List<int> encryptionKey;
   final List<int> authenticationKey;
@@ -35,7 +38,8 @@ class HkdfKeyResult {
 /// cryptography _really_ wants to check the MAC output from AES-256-CBC. Since
 /// we don't have it, we need the MAC check to always "pass".
 class NoMacSecretBox extends SecretBox {
-  NoMacSecretBox(super.cipherText, { required super.nonce }) : super(mac: Mac.empty);
+  NoMacSecretBox(super.cipherText, {required super.nonce})
+      : super(mac: Mac.empty);
 
   @override
   Future<void> checkMac({
@@ -60,12 +64,20 @@ Future<HkdfKeyResult> deriveEncryptionKeys(List<int> input, String info) async {
   );
   final bytes = await result.extractBytes();
 
-  return HkdfKeyResult(bytes.sublist(0, 32), bytes.sublist(32, 64), bytes.sublist(64, 80));
+  return HkdfKeyResult(
+    bytes.sublist(0, 32),
+    bytes.sublist(32, 64),
+    bytes.sublist(64, 80),
+  );
 }
 
 /// A small helper function to make AES-256-CBC easier. Encrypt [plaintext] using [key] as
 /// the encryption key and [iv] as the IV. Returns the ciphertext.
-Future<List<int>> aes256CbcEncrypt(List<int> plaintext, List<int> key, List<int> iv) async {
+Future<List<int>> aes256CbcEncrypt(
+  List<int> plaintext,
+  List<int> key,
+  List<int> iv,
+) async {
   final algorithm = AesCbc.with256bits(
     macAlgorithm: MacAlgorithm.empty,
   );
@@ -80,7 +92,11 @@ Future<List<int>> aes256CbcEncrypt(List<int> plaintext, List<int> key, List<int>
 
 /// A small helper function to make AES-256-CBC easier. Decrypt [ciphertext] using [key] as
 /// the encryption key and [iv] as the IV. Returns the ciphertext.
-Future<List<int>> aes256CbcDecrypt(List<int> ciphertext, List<int> key, List<int> iv) async {
+Future<List<int>> aes256CbcDecrypt(
+  List<int> ciphertext,
+  List<int> key,
+  List<int> iv,
+) async {
   final algorithm = AesCbc.with256bits(
     macAlgorithm: MacAlgorithm.empty,
   );

lib/src/double_ratchet/crypto.dart

@@ -10,12 +10,19 @@ const encryptHkdfInfoString = 'OMEMO Message Key Material';
 /// Signals ENCRYPT function as specified by OMEMO 0.8.3.
 /// Encrypt [plaintext] using the message key [mk], given associated_data [associatedData]
 /// and the AD output from the X3DH [sessionAd].
-Future<List<int>> encrypt(List<int> mk, List<int> plaintext, List<int> associatedData, List<int> sessionAd) async {
+Future<List<int>> encrypt(
+  List<int> mk,
+  List<int> plaintext,
+  List<int> associatedData,
+  List<int> sessionAd,
+) async {
   // Generate encryption, authentication key and IV
   final keys = await deriveEncryptionKeys(mk, encryptHkdfInfoString);
-  final ciphertext = await aes256CbcEncrypt(plaintext, keys.encryptionKey, keys.iv);
+  final ciphertext =
+      await aes256CbcEncrypt(plaintext, keys.encryptionKey, keys.iv);
 
-  final header = OmemoMessage.fromBuffer(associatedData.sublist(sessionAd.length))
+  final header =
+      OmemoMessage.fromBuffer(associatedData.sublist(sessionAd.length))
         ..ciphertext = ciphertext;
   final headerBytes = header.writeToBuffer();
   final hmacInput = concat([sessionAd, headerBytes]);
@@ -29,7 +36,12 @@ Future<List<int>> encrypt(List<int> mk, List<int> plaintext, List<int> associate
 /// Signals DECRYPT function as specified by OMEMO 0.8.3.
 /// Decrypt [ciphertext] with the message key [mk], given the associated_data [associatedData]
 /// and the AD output from the X3DH.
-Future<List<int>> decrypt(List<int> mk, List<int> ciphertext, List<int> associatedData, List<int> sessionAd) async {
+Future<List<int>> decrypt(
+  List<int> mk,
+  List<int> ciphertext,
+  List<int> associatedData,
+  List<int> sessionAd,
+) async {
   // Generate encryption, authentication key and IV
   final keys = await deriveEncryptionKeys(mk, encryptHkdfInfoString);
 

lib/src/double_ratchet/double_ratchet.dart

@@ -1,5 +1,6 @@
 import 'dart:convert';
 import 'package:cryptography/cryptography.dart';
+import 'package:hex/hex.dart';
 import 'package:meta/meta.dart';
 import 'package:omemo_dart/src/crypto.dart';
 import 'package:omemo_dart/src/double_ratchet/crypto.dart';
@@ -13,7 +14,6 @@ import 'package:omemo_dart/src/protobuf/omemo_message.dart';
 const maxSkip = 1000;
 
 class RatchetStep {
-
   const RatchetStep(this.header, this.ciphertext);
   final OmemoMessage header;
   final List<int> ciphertext;
@@ -21,7 +21,6 @@ class RatchetStep {
 
 @immutable
 class SkippedKey {
-
   const SkippedKey(this.dh, this.n);
 
   factory SkippedKey.fromJson(Map<String, dynamic> data) {
@@ -54,7 +53,6 @@ class SkippedKey {
 }
 
 class OmemoDoubleRatchet {
-
   OmemoDoubleRatchet(
     this.dhs, // DHs
     this.dhr, // DHr
@@ -68,6 +66,8 @@ class OmemoDoubleRatchet {
     this.sessionAd,
     this.mkSkipped, // MKSKIPPED
     this.acknowledged,
+    this.kexTimestamp,
+    this.kex,
   );
 
   factory OmemoDoubleRatchet.fromJson(Map<String, dynamic> data) {
@@ -82,9 +82,11 @@ class OmemoDoubleRatchet {
       'ns': 0,
       'nr': 0,
       'pn': 0,
-      'ik_pub': 'base/64/encoded',
+      'ik_pub': null | 'base/64/encoded',
       'session_ad': 'base/64/encoded',
       'acknowledged': true | false,
+      'kex_timestamp': int,
+      'kex': 'base/64/encoded',
       'mkskipped': [
         {
           'key': 'base/64/encoded',
@@ -94,11 +96,21 @@ class OmemoDoubleRatchet {
       ]
     }
     */
-    final mkSkipped = <SkippedKey, List<int>>{};
+    // NOTE: Dart has some issues with just casting a List<dynamic> to List<Map<...>>, as
-    for (final entry in data['mkskipped']! as List<Map<String, dynamic>>) {
+    //       such we need to convert the items by hand.
-      final key = SkippedKey.fromJson(entry);
+    final mkSkipped = Map<SkippedKey, List<int>>.fromEntries(
-      mkSkipped[key] = base64.decode(entry['key']! as String);
+      (data['mkskipped']! as List<dynamic>)
-    }
+          .map<MapEntry<SkippedKey, List<int>>>(
+        (entry) {
+          final map = entry as Map<String, dynamic>;
+          final key = SkippedKey.fromJson(map);
+          return MapEntry(
+            key,
+            base64.decode(map['key']! as String),
+          );
+        },
+      ),
+    );
 
     return OmemoDoubleRatchet(
       OmemoKeyPair.fromBytes(
@@ -120,6 +132,8 @@ class OmemoDoubleRatchet {
       base64.decode(data['session_ad']! as String),
       mkSkipped,
       data['acknowledged']! as bool,
+      data['kex_timestamp']! as int,
+      data['kex'] as String?,
     );
   }
 
@@ -151,6 +165,13 @@ class OmemoDoubleRatchet {
 
   final Map<SkippedKey, List<int>> mkSkipped;
 
+  /// The point in time at which we performed the kex exchange to create this ratchet.
+  /// Precision is milliseconds since epoch.
+  int kexTimestamp;
+
+  /// The key exchange that was used for initiating the session.
+  final String? kex;
+
   /// Indicates whether we received an empty OMEMO message after building a session with
   /// the device.
   bool acknowledged;
@@ -158,7 +179,13 @@ class OmemoDoubleRatchet {
   /// Create an OMEMO session using the Signed Pre Key [spk], the shared secret [sk] that
   /// was obtained using a X3DH and the associated data [ad] that was also obtained through
   /// a X3DH. [ik] refers to Bob's (the receiver's) IK public key.
-  static Future<OmemoDoubleRatchet> initiateNewSession(OmemoPublicKey spk, OmemoPublicKey ik, List<int> sk, List<int> ad) async {
+  static Future<OmemoDoubleRatchet> initiateNewSession(
+    OmemoPublicKey spk,
+    OmemoPublicKey ik,
+    List<int> sk,
+    List<int> ad,
+    int timestamp,
+  ) async {
     final dhs = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
     final dhr = spk;
     final rk = await kdfRk(sk, await omemoDH(dhs, dhr, 0));
@@ -177,6 +204,8 @@ class OmemoDoubleRatchet {
       ad,
       {},
       false,
+      timestamp,
+      '',
     );
   }
 
@@ -184,7 +213,13 @@ class OmemoDoubleRatchet {
   /// Pre Key keypair [spk], the shared secret [sk] that was obtained through a X3DH and
   /// the associated data [ad] that was also obtained through a X3DH. [ik] refers to
   /// Alice's (the initiator's) IK public key.
-  static Future<OmemoDoubleRatchet> acceptNewSession(OmemoKeyPair spk, OmemoPublicKey ik, List<int> sk, List<int> ad) async {
+  static Future<OmemoDoubleRatchet> acceptNewSession(
+    OmemoKeyPair spk,
+    OmemoPublicKey ik,
+    List<int> sk,
+    List<int> ad,
+    int kexTimestamp,
+  ) async {
     return OmemoDoubleRatchet(
       spk,
       null,
@@ -198,11 +233,14 @@ class OmemoDoubleRatchet {
       ad,
       {},
       true,
+      kexTimestamp,
+      null,
     );
   }
 
   Future<Map<String, dynamic>> toJson() async {
-    final mkSkippedSerialised = List<Map<String, dynamic>>.empty(growable: true);
+    final mkSkippedSerialised =
+        List<Map<String, dynamic>>.empty(growable: true);
     for (final entry in mkSkipped.entries) {
       final result = await entry.key.toJson();
       result['key'] = base64.encode(entry.value);
@@ -224,10 +262,21 @@ class OmemoDoubleRatchet {
       'session_ad': base64.encode(sessionAd),
       'mkskipped': mkSkippedSerialised,
       'acknowledged': acknowledged,
+      'kex_timestamp': kexTimestamp,
+      'kex': kex,
     };
   }
 
-  Future<List<int>?> _trySkippedMessageKeys(OmemoMessage header, List<int> ciphertext) async {
+  /// Returns the OMEMO compatible fingerprint of the ratchet session.
+  Future<String> getOmemoFingerprint() async {
+    final curveKey = await ik.toCurve25519();
+    return HEX.encode(await curveKey.getBytes());
+  }
+
+  Future<List<int>?> _trySkippedMessageKeys(
+    OmemoMessage header,
+    List<int> ciphertext,
+  ) async {
     final key = SkippedKey(
       OmemoPublicKey.fromBytes(header.dhPub!, KeyPairType.x25519),
       header.n!,
@@ -236,7 +285,12 @@ class OmemoDoubleRatchet {
       final mk = mkSkipped[key]!;
       mkSkipped.remove(key);
 
-      return decrypt(mk, ciphertext, concat([sessionAd, header.writeToBuffer()]), sessionAd);
+      return decrypt(
+        mk,
+        ciphertext,
+        concat([sessionAd, header.writeToBuffer()]),
+        sessionAd,
+      );
     }
 
     return null;
@@ -259,18 +313,18 @@ class OmemoDoubleRatchet {
   }
 
   Future<void> _dhRatchet(OmemoMessage header) async {
-    pn = header.n!;
+    pn = ns;
     ns = 0;
     nr = 0;
     dhr = OmemoPublicKey.fromBytes(header.dhPub!, KeyPairType.x25519);
 
     final newRk = await kdfRk(rk, await omemoDH(dhs, dhr!, 0));
-    rk = newRk;
+    rk = List.from(newRk);
-    ckr = newRk;
+    ckr = List.from(newRk);
     dhs = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
     final newNewRk = await kdfRk(rk, await omemoDH(dhs, dhr!, 0));
-    rk = newNewRk;
+    rk = List.from(newNewRk);
-    cks = newNewRk;
+    cks = List.from(newNewRk);
   }
 
   /// Encrypt [plaintext] using the Double Ratchet.
@@ -288,7 +342,12 @@ class OmemoDoubleRatchet {
 
     return RatchetStep(
       header,
-      await encrypt(mk, plaintext, concat([sessionAd, header.writeToBuffer()]), sessionAd),
+      await encrypt(
+        mk,
+        plaintext,
+        concat([sessionAd, header.writeToBuffer()]),
+        sessionAd,
+      ),
     );
   }
 
@@ -296,7 +355,10 @@ class OmemoDoubleRatchet {
   /// Ratchet. Returns the decrypted (raw) plaintext.
   ///
   /// Throws an SkippingTooManyMessagesException if too many messages were to be skipped.
-  Future<List<int>> ratchetDecrypt(OmemoMessage header, List<int> ciphertext) async {
+  Future<List<int>> ratchetDecrypt(
+    OmemoMessage header,
+    List<int> ciphertext,
+  ) async {
     // Check if we skipped too many messages
     final plaintext = await _trySkippedMessageKeys(header, ciphertext);
     if (plaintext != null) {
@@ -304,8 +366,8 @@ class OmemoDoubleRatchet {
     }
 
     final dhPubMatches = listsEqual(
-      header.dhPub ?? <int>[],
+      header.dhPub!,
-      await dhr?.getBytes() ?? <int>[],
+      (await dhr?.getBytes()) ?? <int>[],
     );
     if (!dhPubMatches) {
       await _skipMessageKeys(header.pn!);
@@ -318,15 +380,65 @@ class OmemoDoubleRatchet {
     ckr = newCkr;
     nr++;
 
-    return decrypt(mk, ciphertext, concat([sessionAd, header.writeToBuffer()]), sessionAd);
+    return decrypt(
+      mk,
+      ciphertext,
+      concat([sessionAd, header.writeToBuffer()]),
+      sessionAd,
+    );
+  }
+
+  OmemoDoubleRatchet clone() {
+    return OmemoDoubleRatchet(
+      dhs,
+      dhr,
+      rk,
+      cks != null ? List<int>.from(cks!) : null,
+      ckr != null ? List<int>.from(ckr!) : null,
+      ns,
+      nr,
+      pn,
+      ik,
+      sessionAd,
+      Map<SkippedKey, List<int>>.from(mkSkipped),
+      acknowledged,
+      kexTimestamp,
+      kex,
+    );
+  }
+
+  OmemoDoubleRatchet cloneWithKex(String kex) {
+    return OmemoDoubleRatchet(
+      dhs,
+      dhr,
+      rk,
+      cks != null ? List<int>.from(cks!) : null,
+      ckr != null ? List<int>.from(ckr!) : null,
+      ns,
+      nr,
+      pn,
+      ik,
+      sessionAd,
+      Map<SkippedKey, List<int>>.from(mkSkipped),
+      acknowledged,
+      kexTimestamp,
+      kex,
+    );
   }
 
   @visibleForTesting
   Future<bool> equals(OmemoDoubleRatchet other) async {
+    final dhrMatch = dhr == null
+        ? other.dhr == null
+        :
         // ignore: invalid_use_of_visible_for_testing_member
-    final dhrMatch = dhr == null ? other.dhr == null : await dhr!.equals(other.dhr!);
+        other.dhr != null && await dhr!.equals(other.dhr!);
-    final ckrMatch = ckr == null ? other.ckr == null : listsEqual(ckr!, other.ckr!);
+    final ckrMatch = ckr == null
-    final cksMatch = cks == null ? other.cks == null : listsEqual(cks!, other.cks!);
+        ? other.ckr == null
+        : other.ckr != null && listsEqual(ckr!, other.ckr!);
+    final cksMatch = cks == null
+        ? other.cks == null
+        : other.cks != null && listsEqual(cks!, other.cks!);
 
     // ignore: invalid_use_of_visible_for_testing_member
     final dhsMatch = await dhs.equals(other.dhs);
@@ -342,6 +454,7 @@ class OmemoDoubleRatchet {
         ns == other.ns &&
         nr == other.nr &&
         pn == other.pn &&
-      listsEqual(sessionAd, other.sessionAd);
+        listsEqual(sessionAd, other.sessionAd) &&
+        kexTimestamp == other.kexTimestamp;
   }
 }

lib/src/errors.dart

@@ -1,32 +1,61 @@
+abstract class OmemoException {}
+
 /// Triggered during X3DH if the signature if the SPK does verify to the actual SPK.
-class InvalidSignatureException implements Exception {
+class InvalidSignatureException extends OmemoException implements Exception {
-  String errMsg() => 'The signature of the SPK does not match the provided signature';
+  String errMsg() =>
+      'The signature of the SPK does not match the provided signature';
 }
 
 /// Triggered by the Double Ratchet if the computed HMAC does not match the attached HMAC.
 /// Triggered by the Session Manager if the computed HMAC does not match the attached HMAC.
-class InvalidMessageHMACException implements Exception {
+class InvalidMessageHMACException extends OmemoException implements Exception {
   String errMsg() => 'The computed HMAC does not match the provided HMAC';
 }
 
 /// Triggered by the Double Ratchet if skipping messages would cause skipping more than
 /// MAXSKIP messages
-class SkippingTooManyMessagesException implements Exception {
+class SkippingTooManyMessagesException extends OmemoException
+    implements Exception {
   String errMsg() => 'Skipping messages would cause a skip bigger than MAXSKIP';
 }
 
 /// Triggered by the Session Manager if the message key is not encrypted for the device.
-class NotEncryptedForDeviceException implements Exception {
+class NotEncryptedForDeviceException extends OmemoException
+    implements Exception {
   String errMsg() => 'Not encrypted for this device';
 }
 
 /// Triggered by the Session Manager when there is no key for decrypting the message.
-class NoDecryptionKeyException implements Exception {
+class NoDecryptionKeyException extends OmemoException implements Exception {
   String errMsg() => 'No key available for decrypting the message';
 }
 
 /// Triggered by the Session Manager when the identifier of the used Signed Prekey
 /// is neither the current SPK's identifier nor the old one's.
-class UnknownSignedPrekeyException implements Exception {
+class UnknownSignedPrekeyException extends OmemoException implements Exception {
   String errMsg() => 'Unknown Signed Prekey used.';
 }
+
+/// Triggered by the Session Manager when the received Key Exchange message does not meet
+/// the requirement that a key exchange, given that the ratchet already exists, must be
+/// sent after its creation.
+class InvalidKeyExchangeException extends OmemoException implements Exception {
+  String errMsg() => 'The key exchange was sent before the last kex finished';
+}
+
+/// Triggered by the Session Manager when a message's sequence number is smaller than we
+/// expect it to be.
+class MessageAlreadyDecryptedException extends OmemoException
+    implements Exception {
+  String errMsg() => 'The message has already been decrypted';
+}
+
+/// Triggered by the OmemoManager when we could not encrypt a message as we have
+/// no key material available. That happens, for example, when we want to create a
+/// ratchet session with a JID we had no session with but fetching the device bundle
+/// failed.
+class NoKeyMaterialAvailableException extends OmemoException
+    implements Exception {
+  String errMsg() =>
+      'No key material available to create a ratchet session with';
+}

lib/src/helpers.dart

@@ -43,7 +43,11 @@ int generateRandom32BitNumber() {
   return Random.secure().nextInt(4294967295 /*pow(2, 32) - 1*/);
 }
 
-OmemoPublicKey? decodeKeyIfNotNull(Map<String, dynamic> map, String key, KeyPairType type) {
+OmemoPublicKey? decodeKeyIfNotNull(
+  Map<String, dynamic> map,
+  String key,
+  KeyPairType type,
+) {
   if (map[key] == null) return null;
 
   return OmemoPublicKey.fromBytes(
@@ -73,3 +77,7 @@ OmemoKeyPair? decodeKeyPairIfNotNull(String? pk, String? sk, KeyPairType type) {
     type,
   );
 }
+
+int getTimestamp() {
+  return DateTime.now().millisecondsSinceEpoch;
+}

lib/src/keys.dart

@@ -9,7 +9,6 @@ const privateKeyLength = 32;
 const publicKeyLength = 32;
 
 class OmemoPublicKey {
-
   const OmemoPublicKey(this._pubkey);
 
   factory OmemoPublicKey.fromBytes(List<int> bytes, KeyPairType type) {
@@ -32,7 +31,10 @@ class OmemoPublicKey {
   Future<String> asBase64() async => base64Encode(_pubkey.bytes);
 
   Future<OmemoPublicKey> toCurve25519() async {
-    assert(type == KeyPairType.ed25519, 'Cannot convert non-Ed25519 public key to X25519');
+    assert(
+      type == KeyPairType.ed25519,
+      'Cannot convert non-Ed25519 public key to X25519',
+    );
 
     final pkc = Uint8List(publicKeyLength);
     TweetNaClExt.crypto_sign_ed25519_pk_to_x25519_pk(
@@ -40,14 +42,17 @@ class OmemoPublicKey {
       Uint8List.fromList(await getBytes()),
     );
 
-    return OmemoPublicKey(SimplePublicKey(List<int>.from(pkc), type: KeyPairType.x25519));
+    return OmemoPublicKey(
+      SimplePublicKey(List<int>.from(pkc), type: KeyPairType.x25519),
+    );
   }
 
   SimplePublicKey asPublicKey() => _pubkey;
 
   @visibleForTesting
   Future<bool> equals(OmemoPublicKey key) async {
-    return type == key.type && listsEqual(
+    return type == key.type &&
+        listsEqual(
           await getBytes(),
           await key.getBytes(),
         );
@@ -55,7 +60,6 @@ class OmemoPublicKey {
 }
 
 class OmemoPrivateKey {
-
   const OmemoPrivateKey(this._privkey, this.type);
   final List<int> _privkey;
   final KeyPairType type;
@@ -63,7 +67,10 @@ class OmemoPrivateKey {
   Future<List<int>> getBytes() async => _privkey;
 
   Future<OmemoPrivateKey> toCurve25519() async {
-    assert(type == KeyPairType.ed25519, 'Cannot convert non-Ed25519 private key to X25519');
+    assert(
+      type == KeyPairType.ed25519,
+      'Cannot convert non-Ed25519 private key to X25519',
+    );
 
     final skc = Uint8List(privateKeyLength);
     TweetNaClExt.crypto_sign_ed25519_sk_to_x25519_sk(
@@ -76,7 +83,8 @@ class OmemoPrivateKey {
 
   @visibleForTesting
   Future<bool> equals(OmemoPrivateKey key) async {
-    return type == key.type && listsEqual(
+    return type == key.type &&
+        listsEqual(
           await getBytes(),
           await key.getBytes(),
         );
@@ -85,12 +93,15 @@ class OmemoPrivateKey {
 
 /// A generic wrapper class for both Ed25519 and X25519 keypairs
 class OmemoKeyPair {
-
   const OmemoKeyPair(this.pk, this.sk, this.type);
 
   /// Create an OmemoKeyPair just from a [type] and the bytes of the private and public
   /// key.
-  factory OmemoKeyPair.fromBytes(List<int> publicKey, List<int> privateKey, KeyPairType type) {
+  factory OmemoKeyPair.fromBytes(
+    List<int> publicKey,
+    List<int> privateKey,
+    KeyPairType type,
+  ) {
     return OmemoKeyPair(
       OmemoPublicKey.fromBytes(
         publicKey,
@@ -107,7 +118,10 @@ class OmemoKeyPair {
   /// Generate a completely new random OmemoKeyPair of type [type]. [type] must be either
   /// KeyPairType.ed25519 or KeyPairType.x25519.
   static Future<OmemoKeyPair> generateNewPair(KeyPairType type) async {
-    assert(type == KeyPairType.ed25519 || type == KeyPairType.x25519, 'Keypair must be either Ed25519 or X25519');
+    assert(
+      type == KeyPairType.ed25519 || type == KeyPairType.x25519,
+      'Keypair must be either Ed25519 or X25519',
+    );
 
     SimpleKeyPair kp;
     if (type == KeyPairType.ed25519) {
@@ -136,7 +150,10 @@ class OmemoKeyPair {
 
   /// Return the bytes that comprise the public key.
   Future<OmemoKeyPair> toCurve25519() async {
-    assert(type == KeyPairType.ed25519, 'Cannot convert non-Ed25519 keypair to X25519');
+    assert(
+      type == KeyPairType.ed25519,
+      'Cannot convert non-Ed25519 keypair to X25519',
+    );
 
     return OmemoKeyPair(
       await pk.toCurve25519(),

lib/src/omemo/bundle.dart

@@ -1,9 +1,9 @@
 import 'dart:convert';
 import 'package:cryptography/cryptography.dart';
+import 'package:hex/hex.dart';
 import 'package:omemo_dart/src/keys.dart';
 
 class OmemoBundle {
-
   const OmemoBundle(
     this.jid,
     this.id,
@@ -13,17 +13,23 @@ class OmemoBundle {
     this.ikEncoded,
     this.opksEncoded,
   );
+
   /// The bare Jid the Bundle belongs to
   final String jid;
+
   /// The device Id
   final int id;
+
   /// The SPK but base64 encoded
   final String spkEncoded;
   final int spkId;
+
   /// The SPK signature but base64 encoded
   final String spkSignatureEncoded;
+
   /// The IK but base64 encoded
   final String ikEncoded;
+
   /// The mapping of a OPK's id to the base64 encoded data
   final Map<int, String> opksEncoded;
 
@@ -43,4 +49,10 @@ class OmemoBundle {
   }
 
   List<int> get spkSignature => base64Decode(spkSignatureEncoded);
+
+  /// Calculates the fingerprint of the bundle (See
+  /// https://xmpp.org/extensions/xep-0384.html#security § 2).
+  Future<String> getFingerprint() async {
+    return HEX.encode(await ik.getBytes());
+  }
 }

lib/src/omemo/constants.dart

@@ -0,0 +1,2 @@
+/// The info used for when encrypting the AES key for the actual payload.
+const omemoPayloadInfoString = 'OMEMO Payload';

lib/src/omemo/decryption_result.dart

@@ -0,0 +1,9 @@
+import 'package:meta/meta.dart';
+import 'package:omemo_dart/src/errors.dart';
+
+@immutable
+class DecryptionResult {
+  const DecryptionResult(this.payload, this.error);
+  final String? payload;
+  final OmemoException? error;
+}

lib/src/omemo/device.dart

@@ -1,5 +1,6 @@
 import 'dart:convert';
 import 'package:cryptography/cryptography.dart';
+import 'package:hex/hex.dart';
 import 'package:meta/meta.dart';
 import 'package:omemo_dart/src/helpers.dart';
 import 'package:omemo_dart/src/keys.dart';
@@ -8,9 +9,8 @@ import 'package:omemo_dart/src/x3dh/x3dh.dart';
 
 /// This class represents an OmemoBundle but with all keypairs belonging to the keys
 @immutable
-class Device {
+class OmemoDevice {
-
+  const OmemoDevice(
-  const Device(
     this.jid,
     this.id,
     this.ik,
@@ -23,7 +23,7 @@ class Device {
   );
 
   /// Deserialize the Device
-  factory Device.fromJson(Map<String, dynamic> data) {
+  factory OmemoDevice.fromJson(Map<String, dynamic> data) {
     // NOTE: We use the way OpenSSH names their keys, meaning that ik is the Identity
     //       Keypair's private key, while ik_pub refers to the Identity Keypair's public
     //       key.
@@ -49,16 +49,25 @@ class Device {
       ]
     }
     */
-    final opks = <int, OmemoKeyPair>{};
+    // NOTE: Dart has some issues with just casting a List<dynamic> to List<Map<...>>, as
-    for (final opk in data['opks']! as List<Map<String, dynamic>>) {
+    //       such we need to convert the items by hand.
-      opks[opk['id']! as int] = OmemoKeyPair.fromBytes(
+    final opks = Map<int, OmemoKeyPair>.fromEntries(
-        base64.decode(opk['public']! as String),
+      (data['opks']! as List<dynamic>).map<MapEntry<int, OmemoKeyPair>>(
-        base64.decode(opk['private']! as String),
+        (opk) {
+          final map = opk as Map<String, dynamic>;
+          return MapEntry(
+            map['id']! as int,
+            OmemoKeyPair.fromBytes(
+              base64.decode(map['public']! as String),
+              base64.decode(map['private']! as String),
               KeyPairType.x25519,
+            ),
+          );
+        },
+      ),
     );
-    }
 
-    return Device(
+    return OmemoDevice(
       data['jid']! as String,
       data['id']! as int,
       OmemoKeyPair.fromBytes(
@@ -84,7 +93,10 @@ class Device {
   }
 
   /// Generate a completely new device, i.e. cryptographic identity.
-  static Future<Device> generateNewDevice(String jid, { int opkAmount = 100 }) async {
+  static Future<OmemoDevice> generateNewDevice(
+    String jid, {
+    int opkAmount = 100,
+  }) async {
     final id = generateRandom32BitNumber();
     final ik = await OmemoKeyPair.generateNewPair(KeyPairType.ed25519);
     final spk = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
@@ -96,7 +108,7 @@ class Device {
       opks[i] = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
     }
 
-    return Device(jid, id, ik, spk, spkId, signature, null, null, opks);
+    return OmemoDevice(jid, id, ik, spk, spkId, signature, null, null, opks);
   }
 
   /// Our bare Jid
@@ -110,13 +122,16 @@ class Device {
 
   /// The signed prekey...
   final OmemoKeyPair spk;
+
   /// ...its Id, ...
   final int spkId;
+
   /// ...and its signature
   final List<int> spkSignature;
 
   /// The old Signed Prekey...
   final OmemoKeyPair? oldSpk;
+
   /// ...and its Id
   final int? oldSpkId;
 
@@ -126,12 +141,12 @@ class Device {
   /// This replaces the Onetime-Prekey with id [id] with a completely new one. Returns
   /// a new Device object that copies over everything but replaces said key.
   @internal
-  Future<Device> replaceOnetimePrekey(int id) async {
+  Future<OmemoDevice> replaceOnetimePrekey(int id) async {
     opks[id] = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
 
-    return Device(
+    return OmemoDevice(
       jid,
-      id,
+      this.id,
       ik,
       spk,
       spkId,
@@ -145,12 +160,12 @@ class Device {
   /// This replaces the Signed-Prekey with a completely new one. Returns a new Device object
   /// that copies over everything but replaces the Signed-Prekey and its signature.
   @internal
-  Future<Device> replaceSignedPrekey() async {
+  Future<OmemoDevice> replaceSignedPrekey() async {
     final newSpk = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
     final newSpkId = generateRandom32BitNumber();
     final newSignature = await sig(ik, await newSpk.pk.getBytes());
 
-    return Device(
+    return OmemoDevice(
       jid,
       id,
       ik,
@@ -166,8 +181,8 @@ class Device {
   /// Returns a new device that is equal to this one with the exception that the new
   /// device's id is a new number between 0 and 2**32 - 1.
   @internal
-  Device withNewId() {
+  OmemoDevice withNewId() {
-    return Device(
+    return OmemoDevice(
       jid,
       generateRandom32BitNumber(),
       ik,
@@ -199,6 +214,13 @@ class Device {
     );
   }
 
+  /// Returns the fingerprint of the current device
+  Future<String> getFingerprint() async {
+    // Since the local key is Ed25519, we must convert it to Curve25519 first
+    final curveKey = await ik.pk.toCurve25519();
+    return HEX.encode(await curveKey.getBytes());
+  }
+
   /// Serialise the device information.
   Future<Map<String, dynamic>> toJson() async {
     /// Serialise the OPKs
@@ -228,14 +250,16 @@ class Device {
   }
 
   @visibleForTesting
-  Future<bool> equals(Device other) async {
+  Future<bool> equals(OmemoDevice other) async {
     var opksMatch = true;
     if (opks.length != other.opks.length) {
       opksMatch = false;
     } else {
       for (final entry in opks.entries) {
         // ignore: invalid_use_of_visible_for_testing_member
-        final matches = await other.opks[entry.key]?.equals(entry.value) ?? false;
+        final matches =
+            // ignore: invalid_use_of_visible_for_testing_member
+            await other.opks[entry.key]?.equals(entry.value) ?? false;
         if (!matches) {
           opksMatch = false;
         }
@@ -247,7 +271,10 @@ class Device {
     // ignore: invalid_use_of_visible_for_testing_member
     final spkMatch = await spk.equals(other.spk);
     // ignore: invalid_use_of_visible_for_testing_member
-    final oldSpkMatch = oldSpk != null ? await oldSpk!.equals(other.oldSpk!) : other.oldSpk == null;
+    final oldSpkMatch = oldSpk != null
+        // ignore: invalid_use_of_visible_for_testing_member
+        ? await oldSpk!.equals(other.oldSpk!)
+        : other.oldSpk == null;
     return id == other.id &&
         ikMatch &&
         spkMatch &&

lib/src/omemo/encrypted_key.dart

@@ -4,7 +4,6 @@ import 'package:meta/meta.dart';
 /// <keys /> header.
 @immutable
 class EncryptedKey {
-
   const EncryptedKey(this.jid, this.rid, this.value, this.kex);
   final String jid;
   final int rid;

lib/src/omemo/encryption_result.dart

@@ -1,15 +1,33 @@
 import 'package:meta/meta.dart';
+import 'package:omemo_dart/src/errors.dart';
 import 'package:omemo_dart/src/omemo/encrypted_key.dart';
+import 'package:omemo_dart/src/omemo/ratchet_map_key.dart';
 
 @immutable
 class EncryptionResult {
+  const EncryptionResult(
+    this.ciphertext,
+    this.encryptedKeys,
+    this.deviceEncryptionErrors,
+    this.jidEncryptionErrors,
+  );
 
-  const EncryptionResult(this.ciphertext, this.encryptedKeys);
+  /// The actual message that was encrypted.
-  
-  /// The actual message that was encrypted
   final List<int>? ciphertext;
 
   /// Mapping of the device Id to the key for decrypting ciphertext, encrypted
-  /// for the ratchet with said device Id
+  /// for the ratchet with said device Id.
   final List<EncryptedKey> encryptedKeys;
+
+  /// Mapping of a ratchet map keys to a possible exception.
+  final Map<RatchetMapKey, OmemoException> deviceEncryptionErrors;
+
+  /// Mapping of a JID to a possible exception.
+  final Map<String, OmemoException> jidEncryptionErrors;
+
+  /// True if the encryption was a success. This means that we could encrypt for
+  /// at least one ratchet.
+  bool isSuccess(int numberOfRecipients) =>
+      encryptedKeys.isNotEmpty &&
+      jidEncryptionErrors.length < numberOfRecipients;
 }

lib/src/omemo/events.dart

@@ -5,32 +5,40 @@ abstract class OmemoEvent {}
 
 /// Triggered when a ratchet has been modified
 class RatchetModifiedEvent extends OmemoEvent {
-
+  RatchetModifiedEvent(
-  RatchetModifiedEvent(this.jid, this.deviceId, this.ratchet);
+    this.jid,
+    this.deviceId,
+    this.ratchet,
+    this.added,
+    this.replaced,
+  );
   final String jid;
   final int deviceId;
   final OmemoDoubleRatchet ratchet;
+
+  /// Indicates whether the ratchet has just been created (true) or just modified (false).
+  final bool added;
+
+  /// Indicates whether the ratchet has been replaced (true) or not.
+  final bool replaced;
 }
 
 /// Triggered when a ratchet has been removed and should be removed from storage.
 class RatchetRemovedEvent extends OmemoEvent {
-
   RatchetRemovedEvent(this.jid, this.deviceId);
   final String jid;
   final int deviceId;
 }
 
 /// Triggered when the device map has been modified
-class DeviceMapModifiedEvent extends OmemoEvent {
+class DeviceListModifiedEvent extends OmemoEvent {
-
+  DeviceListModifiedEvent(this.list);
-  DeviceMapModifiedEvent(this.map);
+  final Map<String, List<int>> list;
-  final Map<String, List<int>> map;
 }
 
 /// Triggered by the OmemoSessionManager when our own device bundle was modified
 /// and thus should be republished.
 class DeviceModifiedEvent extends OmemoEvent {
-
   DeviceModifiedEvent(this.device);
-  final Device device;
+  final OmemoDevice device;
 }

lib/src/omemo/fingerprint.dart

@@ -2,7 +2,6 @@ import 'package:meta/meta.dart';
 
 @immutable
 class DeviceFingerprint {
-
   const DeviceFingerprint(this.deviceId, this.fingerprint);
   final String fingerprint;
   final int deviceId;

lib/src/omemo/omemomanager.dart

@@ -0,0 +1,854 @@
+import 'dart:async';
+import 'dart:collection';
+import 'dart:convert';
+import 'package:collection/collection.dart';
+import 'package:cryptography/cryptography.dart';
+import 'package:hex/hex.dart';
+import 'package:logging/logging.dart';
+import 'package:meta/meta.dart';
+import 'package:omemo_dart/src/crypto.dart';
+import 'package:omemo_dart/src/double_ratchet/double_ratchet.dart';
+import 'package:omemo_dart/src/errors.dart';
+import 'package:omemo_dart/src/helpers.dart';
+import 'package:omemo_dart/src/keys.dart';
+import 'package:omemo_dart/src/omemo/bundle.dart';
+import 'package:omemo_dart/src/omemo/constants.dart';
+import 'package:omemo_dart/src/omemo/decryption_result.dart';
+import 'package:omemo_dart/src/omemo/device.dart';
+import 'package:omemo_dart/src/omemo/encrypted_key.dart';
+import 'package:omemo_dart/src/omemo/encryption_result.dart';
+import 'package:omemo_dart/src/omemo/events.dart';
+import 'package:omemo_dart/src/omemo/fingerprint.dart';
+import 'package:omemo_dart/src/omemo/ratchet_map_key.dart';
+import 'package:omemo_dart/src/omemo/stanza.dart';
+import 'package:omemo_dart/src/protobuf/omemo_authenticated_message.dart';
+import 'package:omemo_dart/src/protobuf/omemo_key_exchange.dart';
+import 'package:omemo_dart/src/protobuf/omemo_message.dart';
+import 'package:omemo_dart/src/trust/base.dart';
+import 'package:omemo_dart/src/x3dh/x3dh.dart';
+import 'package:synchronized/synchronized.dart';
+
+class _InternalDecryptionResult {
+  const _InternalDecryptionResult(
+    this.ratchetCreated,
+    this.ratchetReplaced,
+    this.payload,
+  ) : assert(
+          !ratchetCreated || !ratchetReplaced,
+          'Ratchet must be either replaced or created',
+        );
+  final bool ratchetCreated;
+  final bool ratchetReplaced;
+  final String? payload;
+}
+
+class OmemoManager {
+  OmemoManager(
+    this._device,
+    this._trustManager,
+    this.sendEmptyOmemoMessageImpl,
+    this.fetchDeviceListImpl,
+    this.fetchDeviceBundleImpl,
+    this.subscribeToDeviceListNodeImpl,
+  );
+
+  final Logger _log = Logger('OmemoManager');
+
+  /// Functions for connecting with the OMEMO library
+
+  /// Send an empty OMEMO:2 message using the encrypted payload @result to
+  /// @recipientJid.
+  final Future<void> Function(EncryptionResult result, String recipientJid)
+      sendEmptyOmemoMessageImpl;
+
+  /// Fetch the list of device ids associated with @jid. If the device list cannot be
+  /// fetched, return null.
+  final Future<List<int>?> Function(String jid) fetchDeviceListImpl;
+
+  /// Fetch the device bundle for the device with id @id of jid. If it cannot be fetched, return null.
+  final Future<OmemoBundle?> Function(String jid, int id) fetchDeviceBundleImpl;
+
+  /// Subscribe to the device list PEP node of @jid.
+  final Future<void> Function(String jid) subscribeToDeviceListNodeImpl;
+
+  /// Map bare JID to its known devices
+  Map<String, List<int>> _deviceList = {};
+
+  /// Map bare JIDs to whether we already requested the device list once
+  final Map<String, bool> _deviceListRequested = {};
+
+  /// Map bare a ratchet key to its ratchet. Note that this is also locked by
+  /// _ratchetCriticalSectionLock.
+  Map<RatchetMapKey, OmemoDoubleRatchet> _ratchetMap = {};
+
+  /// Map bare JID to whether we already tried to subscribe to the device list node.
+  final Map<String, bool> _subscriptionMap = {};
+
+  /// For preventing a race condition in encryption/decryption
+  final Map<String, Queue<Completer<void>>> _ratchetCriticalSectionQueue = {};
+  final Lock _ratchetCriticalSectionLock = Lock();
+
+  /// The OmemoManager's trust management
+  final TrustManager _trustManager;
+  TrustManager get trustManager => _trustManager;
+
+  /// Our own keys...
+  final Lock _deviceLock = Lock();
+  // ignore: prefer_final_fields
+  OmemoDevice _device;
+
+  /// The event bus of the session manager
+  final StreamController<OmemoEvent> _eventStreamController =
+      StreamController<OmemoEvent>.broadcast();
+  Stream<OmemoEvent> get eventStream => _eventStreamController.stream;
+
+  /// Enter the critical section for performing cryptographic operations on the ratchets
+  Future<void> _enterRatchetCriticalSection(String jid) async {
+    final completer = await _ratchetCriticalSectionLock.synchronized(() {
+      if (_ratchetCriticalSectionQueue.containsKey(jid)) {
+        final c = Completer<void>();
+        _ratchetCriticalSectionQueue[jid]!.addLast(c);
+        return c;
+      }
+
+      _ratchetCriticalSectionQueue[jid] = Queue();
+      return null;
+    });
+
+    if (completer != null) {
+      await completer.future;
+    }
+  }
+
+  /// Leave the critical section for the ratchets.
+  Future<void> _leaveRatchetCriticalSection(String jid) async {
+    await _ratchetCriticalSectionLock.synchronized(() {
+      if (_ratchetCriticalSectionQueue.containsKey(jid)) {
+        if (_ratchetCriticalSectionQueue[jid]!.isEmpty) {
+          _ratchetCriticalSectionQueue.remove(jid);
+        } else {
+          _ratchetCriticalSectionQueue[jid]!.removeFirst().complete();
+        }
+      }
+    });
+  }
+
+  Future<String?> _decryptAndVerifyHmac(
+    List<int>? ciphertext,
+    List<int> keyAndHmac,
+  ) async {
+    // Empty OMEMO messages should just have the key decrypted and/or session set up.
+    if (ciphertext == null) {
+      return null;
+    }
+
+    final key = keyAndHmac.sublist(0, 32);
+    final hmac = keyAndHmac.sublist(32, 48);
+    final derivedKeys = await deriveEncryptionKeys(key, omemoPayloadInfoString);
+    final computedHmac =
+        await truncatedHmac(ciphertext, derivedKeys.authenticationKey);
+    if (!listsEqual(hmac, computedHmac)) {
+      throw InvalidMessageHMACException();
+    }
+
+    return utf8.decode(
+      await aes256CbcDecrypt(
+        ciphertext,
+        derivedKeys.encryptionKey,
+        derivedKeys.iv,
+      ),
+    );
+  }
+
+  /// Add a session [ratchet] with the [deviceId] to the internal tracking state.
+  /// NOTE: Must be called from within the ratchet critical section.
+  void _addSession(String jid, int deviceId, OmemoDoubleRatchet ratchet) {
+    // Add the bundle Id
+    if (!_deviceList.containsKey(jid)) {
+      _deviceList[jid] = [deviceId];
+
+      // Commit the device map
+      _eventStreamController.add(DeviceListModifiedEvent(_deviceList));
+    } else {
+      // Prevent having the same device multiple times in the list
+      if (!_deviceList[jid]!.contains(deviceId)) {
+        _deviceList[jid]!.add(deviceId);
+
+        // Commit the device map
+        _eventStreamController.add(DeviceListModifiedEvent(_deviceList));
+      }
+    }
+
+    // Add the ratchet session
+    final key = RatchetMapKey(jid, deviceId);
+    _ratchetMap[key] = ratchet;
+
+    // Commit the ratchet
+    _eventStreamController
+        .add(RatchetModifiedEvent(jid, deviceId, ratchet, true, false));
+  }
+
+  /// Build a new session with the user at [jid] with the device [deviceId] using data
+  /// from the key exchange [kex]. In case [kex] contains an unknown Signed Prekey
+  /// identifier an UnknownSignedPrekeyException will be thrown.
+  Future<OmemoDoubleRatchet> _addSessionFromKeyExchange(
+    String jid,
+    int deviceId,
+    OmemoKeyExchange kex,
+  ) async {
+    // Pick the correct SPK
+    final device = await getDevice();
+    OmemoKeyPair spk;
+    if (kex.spkId == _device.spkId) {
+      spk = _device.spk;
+    } else if (kex.spkId == _device.oldSpkId) {
+      spk = _device.oldSpk!;
+    } else {
+      throw UnknownSignedPrekeyException();
+    }
+
+    final kexResult = await x3dhFromInitialMessage(
+      X3DHMessage(
+        OmemoPublicKey.fromBytes(kex.ik!, KeyPairType.ed25519),
+        OmemoPublicKey.fromBytes(kex.ek!, KeyPairType.x25519),
+        kex.pkId!,
+      ),
+      spk,
+      device.opks.values.elementAt(kex.pkId!),
+      device.ik,
+    );
+    final ratchet = await OmemoDoubleRatchet.acceptNewSession(
+      spk,
+      OmemoPublicKey.fromBytes(kex.ik!, KeyPairType.ed25519),
+      kexResult.sk,
+      kexResult.ad,
+      getTimestamp(),
+    );
+
+    // Notify the trust manager
+    await trustManager.onNewSession(jid, deviceId);
+
+    return ratchet;
+  }
+
+  /// Create a ratchet session initiated by Alice to the user with Jid [jid] and the device
+  /// [deviceId] from the bundle [bundle].
+  @visibleForTesting
+  Future<OmemoKeyExchange> addSessionFromBundle(
+    String jid,
+    int deviceId,
+    OmemoBundle bundle,
+  ) async {
+    final device = await getDevice();
+    final kexResult = await x3dhFromBundle(
+      bundle,
+      device.ik,
+    );
+    final ratchet = await OmemoDoubleRatchet.initiateNewSession(
+      bundle.spk,
+      bundle.ik,
+      kexResult.sk,
+      kexResult.ad,
+      getTimestamp(),
+    );
+
+    await _trustManager.onNewSession(jid, deviceId);
+    _addSession(jid, deviceId, ratchet);
+
+    return OmemoKeyExchange()
+      ..pkId = kexResult.opkId
+      ..spkId = bundle.spkId
+      ..ik = await device.ik.pk.getBytes()
+      ..ek = await kexResult.ek.pk.getBytes();
+  }
+
+  /// In case a decryption error occurs, the Double Ratchet spec says to just restore
+  /// the ratchet to its old state. As such, this function restores the ratchet at
+  /// [mapKey] with [oldRatchet].
+  /// NOTE: Must be called from within the ratchet critical section
+  void _restoreRatchet(RatchetMapKey mapKey, OmemoDoubleRatchet oldRatchet) {
+    _log.finest(
+      'Restoring ratchet ${mapKey.jid}:${mapKey.deviceId} to ${oldRatchet.nr}',
+    );
+    _ratchetMap[mapKey] = oldRatchet;
+
+    // Commit the ratchet
+    _eventStreamController.add(
+      RatchetModifiedEvent(
+        mapKey.jid,
+        mapKey.deviceId,
+        oldRatchet,
+        false,
+        false,
+      ),
+    );
+  }
+
+  /// Attempt to decrypt [ciphertext]. [keys] refers to the <key /> elements inside the
+  /// <keys /> element with a "jid" attribute matching our own. [senderJid] refers to the
+  /// bare Jid of the sender. [senderDeviceId] refers to the "sid" attribute of the
+  /// <encrypted /> element.
+  /// [timestamp] refers to the time the message was sent. This might be either what the
+  /// server tells you via "XEP-0203: Delayed Delivery" or the point in time at which
+  /// you received the stanza, if no Delayed Delivery element was found.
+  ///
+  /// If the received message is an empty OMEMO message, i.e. there is no <payload />
+  /// element, then [ciphertext] must be set to null. In this case, this function
+  /// will return null as there is no message to be decrypted. This, however, is used
+  /// to set up sessions or advance the ratchets.
+  Future<_InternalDecryptionResult> _decryptMessage(
+    List<int>? ciphertext,
+    String senderJid,
+    int senderDeviceId,
+    List<EncryptedKey> keys,
+    int timestamp,
+  ) async {
+    // Try to find a session we can decrypt with.
+    var device = await getDevice();
+    final rawKey = keys.firstWhereOrNull((key) => key.rid == device.id);
+    if (rawKey == null) {
+      throw NotEncryptedForDeviceException();
+    }
+
+    final decodedRawKey = base64.decode(rawKey.value);
+    List<int>? keyAndHmac;
+    OmemoAuthenticatedMessage authMessage;
+    OmemoMessage? message;
+
+    // If the ratchet already existed, we store it. If it didn't, oldRatchet will stay
+    // null.
+    final ratchetKey = RatchetMapKey(senderJid, senderDeviceId);
+    final oldRatchet = getRatchet(ratchetKey)?.clone();
+    if (rawKey.kex) {
+      final kex = OmemoKeyExchange.fromBuffer(decodedRawKey);
+      authMessage = kex.message!;
+      message = OmemoMessage.fromBuffer(authMessage.message!);
+
+      // Guard against old key exchanges
+      if (oldRatchet != null) {
+        _log.finest(
+          'KEX for existent ratchet ${ratchetKey.toJsonKey()}. ${oldRatchet.kexTimestamp} > $timestamp: ${oldRatchet.kexTimestamp > timestamp}',
+        );
+        if (oldRatchet.kexTimestamp > timestamp) {
+          throw InvalidKeyExchangeException();
+        }
+      }
+
+      final r =
+          await _addSessionFromKeyExchange(senderJid, senderDeviceId, kex);
+
+      // Try to decrypt with the new ratchet r
+      try {
+        keyAndHmac =
+            await r.ratchetDecrypt(message, authMessage.writeToBuffer());
+        final result = await _decryptAndVerifyHmac(ciphertext, keyAndHmac);
+
+        // Add the new ratchet
+        _addSession(senderJid, senderDeviceId, r);
+
+        // Replace the OPK
+        await _deviceLock.synchronized(() async {
+          device = await device.replaceOnetimePrekey(kex.pkId!);
+
+          // Commit the device
+          _eventStreamController.add(DeviceModifiedEvent(device));
+        });
+
+        // Commit the ratchet
+        _eventStreamController.add(
+          RatchetModifiedEvent(
+            senderJid,
+            senderDeviceId,
+            r,
+            oldRatchet == null,
+            oldRatchet != null,
+          ),
+        );
+
+        return _InternalDecryptionResult(
+          oldRatchet == null,
+          oldRatchet != null,
+          result,
+        );
+      } catch (ex) {
+        _log.finest('Kex failed due to $ex. Not proceeding with kex.');
+      }
+    } else {
+      authMessage = OmemoAuthenticatedMessage.fromBuffer(decodedRawKey);
+      message = OmemoMessage.fromBuffer(authMessage.message!);
+    }
+
+    final devices = _deviceList[senderJid];
+    if (devices?.contains(senderDeviceId) != true) {
+      throw NoDecryptionKeyException();
+    }
+
+    // TODO(PapaTutuWawa): When receiving a message that is not an OMEMOKeyExchange from a device there is no session with, clients SHOULD create a session with that device and notify it about the new session by responding with an empty OMEMO message as per Sending a message.
+
+    // We can guarantee that the ratchet exists at this point in time
+    final ratchet = getRatchet(ratchetKey)!;
+
+    try {
+      if (rawKey.kex) {
+        keyAndHmac =
+            await ratchet.ratchetDecrypt(message, authMessage.writeToBuffer());
+      } else {
+        keyAndHmac = await ratchet.ratchetDecrypt(message, decodedRawKey);
+      }
+    } catch (_) {
+      _restoreRatchet(ratchetKey, oldRatchet!);
+      rethrow;
+    }
+
+    // Commit the ratchet
+    _eventStreamController.add(
+      RatchetModifiedEvent(
+        senderJid,
+        senderDeviceId,
+        ratchet,
+        false,
+        false,
+      ),
+    );
+
+    try {
+      return _InternalDecryptionResult(
+        false,
+        false,
+        await _decryptAndVerifyHmac(ciphertext, keyAndHmac),
+      );
+    } catch (_) {
+      _restoreRatchet(ratchetKey, oldRatchet!);
+      rethrow;
+    }
+  }
+
+  /// Returns, if it exists, the ratchet associated with [key].
+  /// NOTE: Must be called from within the ratchet critical section.
+  @visibleForTesting
+  OmemoDoubleRatchet? getRatchet(RatchetMapKey key) => _ratchetMap[key];
+
+  /// Figure out what bundles we have to still build a session with.
+  Future<List<OmemoBundle>> _fetchNewBundles(String jid) async {
+    // Check if we already requested the device list for [jid]
+    List<int> bundlesToFetch;
+    if (!_deviceListRequested.containsKey(jid) ||
+        !_deviceList.containsKey(jid)) {
+      // We don't have an up-to-date version of the device list
+      final newDeviceList = await fetchDeviceListImpl(jid);
+      if (newDeviceList == null) return [];
+
+      _deviceList[jid] = newDeviceList;
+      bundlesToFetch = newDeviceList.where((id) {
+        return !_ratchetMap.containsKey(RatchetMapKey(jid, id)) ||
+            _deviceList[jid]?.contains(id) == false;
+      }).toList();
+
+      // Trigger an event with the new device list
+      _eventStreamController.add(DeviceListModifiedEvent(_deviceList));
+    } else {
+      // We already have an up-to-date version of the device list
+      bundlesToFetch = _deviceList[jid]!
+          .where((id) => !_ratchetMap.containsKey(RatchetMapKey(jid, id)))
+          .toList();
+    }
+
+    if (bundlesToFetch.isNotEmpty) {
+      _log.finest('Fetching bundles $bundlesToFetch for $jid');
+    }
+
+    final device = await getDevice();
+    final newBundles = List<OmemoBundle>.empty(growable: true);
+    for (final id in bundlesToFetch) {
+      if (jid == device.jid && id == device.id) continue;
+
+      final bundle = await fetchDeviceBundleImpl(jid, id);
+      if (bundle != null) newBundles.add(bundle);
+    }
+
+    return newBundles;
+  }
+
+  /// Encrypt the key [plaintext] for all known bundles of the Jids in [jids]. Returns a
+  /// map that maps the device Id to the ciphertext of [plaintext].
+  ///
+  /// If [plaintext] is null, then the result will be an empty OMEMO message, i.e. one that
+  /// does not contain a <payload /> element. This means that the ciphertext attribute of
+  /// the result will be null as well.
+  /// NOTE: Must be called within the ratchet critical section
+  Future<EncryptionResult> _encryptToJids(
+    List<String> jids,
+    String? plaintext,
+  ) async {
+    final encryptedKeys = List<EncryptedKey>.empty(growable: true);
+
+    var ciphertext = const <int>[];
+    var keyPayload = const <int>[];
+    if (plaintext != null) {
+      // Generate the key and encrypt the plaintext
+      final key = generateRandomBytes(32);
+      final keys = await deriveEncryptionKeys(key, omemoPayloadInfoString);
+      ciphertext = await aes256CbcEncrypt(
+        utf8.encode(plaintext),
+        keys.encryptionKey,
+        keys.iv,
+      );
+      final hmac = await truncatedHmac(ciphertext, keys.authenticationKey);
+      keyPayload = concat([key, hmac]);
+    } else {
+      keyPayload = List<int>.filled(32, 0x0);
+    }
+
+    final kex = <RatchetMapKey, OmemoKeyExchange>{};
+    for (final jid in jids) {
+      for (final newSession in await _fetchNewBundles(jid)) {
+        kex[RatchetMapKey(jid, newSession.id)] = await addSessionFromBundle(
+          newSession.jid,
+          newSession.id,
+          newSession,
+        );
+      }
+    }
+
+    // We assume that the user already checked if the session exists
+    final deviceEncryptionErrors = <RatchetMapKey, OmemoException>{};
+    final jidEncryptionErrors = <String, OmemoException>{};
+    for (final jid in jids) {
+      final devices = _deviceList[jid];
+      if (devices == null) {
+        _log.severe('Device list does not exist for $jid.');
+        jidEncryptionErrors[jid] = NoKeyMaterialAvailableException();
+        continue;
+      }
+
+      if (!_subscriptionMap.containsKey(jid)) {
+        unawaited(subscribeToDeviceListNodeImpl(jid));
+        _subscriptionMap[jid] = true;
+      }
+
+      for (final deviceId in devices) {
+        // Empty OMEMO messages are allowed to bypass trust
+        if (plaintext != null) {
+          // Only encrypt to devices that are trusted
+          if (!(await _trustManager.isTrusted(jid, deviceId))) continue;
+
+          // Only encrypt to devices that are enabled
+          if (!(await _trustManager.isEnabled(jid, deviceId))) continue;
+        }
+
+        final ratchetKey = RatchetMapKey(jid, deviceId);
+        var ratchet = _ratchetMap[ratchetKey];
+        if (ratchet == null) {
+          _log.severe('Ratchet ${ratchetKey.toJsonKey()} does not exist.');
+          deviceEncryptionErrors[ratchetKey] =
+              NoKeyMaterialAvailableException();
+          continue;
+        }
+
+        final ciphertext =
+            (await ratchet.ratchetEncrypt(keyPayload)).ciphertext;
+
+        if (kex.containsKey(ratchetKey)) {
+          // The ratchet did not exist
+          final k = kex[ratchetKey]!
+            ..message = OmemoAuthenticatedMessage.fromBuffer(ciphertext);
+          final buffer = base64.encode(k.writeToBuffer());
+          encryptedKeys.add(
+            EncryptedKey(
+              jid,
+              deviceId,
+              buffer,
+              true,
+            ),
+          );
+
+          ratchet = ratchet.cloneWithKex(buffer);
+          _ratchetMap[ratchetKey] = ratchet;
+        } else if (!ratchet.acknowledged) {
+          // The ratchet exists but is not acked
+          if (ratchet.kex != null) {
+            final oldKex =
+                OmemoKeyExchange.fromBuffer(base64.decode(ratchet.kex!))
+                  ..message = OmemoAuthenticatedMessage.fromBuffer(ciphertext);
+
+            encryptedKeys.add(
+              EncryptedKey(
+                jid,
+                deviceId,
+                base64.encode(oldKex.writeToBuffer()),
+                true,
+              ),
+            );
+          } else {
+            // The ratchet is not acked but we don't have the old key exchange
+            _log.warning(
+              'Ratchet for $jid:$deviceId is not acked but the kex attribute is null',
+            );
+            encryptedKeys.add(
+              EncryptedKey(
+                jid,
+                deviceId,
+                base64.encode(ciphertext),
+                false,
+              ),
+            );
+          }
+        } else {
+          // The ratchet exists and is acked
+          encryptedKeys.add(
+            EncryptedKey(
+              jid,
+              deviceId,
+              base64.encode(ciphertext),
+              false,
+            ),
+          );
+        }
+
+        // Commit the ratchet
+        _eventStreamController
+            .add(RatchetModifiedEvent(jid, deviceId, ratchet, false, false));
+      }
+    }
+
+    return EncryptionResult(
+      plaintext != null ? ciphertext : null,
+      encryptedKeys,
+      deviceEncryptionErrors,
+      jidEncryptionErrors,
+    );
+  }
+
+  /// Call when receiving an OMEMO:2 encrypted stanza. Will handle everything and
+  /// decrypt it.
+  Future<DecryptionResult> onIncomingStanza(OmemoIncomingStanza stanza) async {
+    await _enterRatchetCriticalSection(stanza.bareSenderJid);
+
+    if (!_subscriptionMap.containsKey(stanza.bareSenderJid)) {
+      unawaited(subscribeToDeviceListNodeImpl(stanza.bareSenderJid));
+      _subscriptionMap[stanza.bareSenderJid] = true;
+    }
+
+    final ratchetKey =
+        RatchetMapKey(stanza.bareSenderJid, stanza.senderDeviceId);
+    final _InternalDecryptionResult result;
+    try {
+      result = await _decryptMessage(
+        stanza.payload != null ? base64.decode(stanza.payload!) : null,
+        stanza.bareSenderJid,
+        stanza.senderDeviceId,
+        stanza.keys,
+        stanza.timestamp,
+      );
+    } on OmemoException catch (ex) {
+      await _leaveRatchetCriticalSection(stanza.bareSenderJid);
+      return DecryptionResult(
+        null,
+        ex,
+      );
+    }
+
+    // Check if the ratchet is acked
+    final ratchet = getRatchet(ratchetKey);
+    assert(
+      ratchet != null,
+      'We decrypted the message, so the ratchet must exist',
+    );
+
+    if (ratchet!.acknowledged) {
+      // Ratchet is acknowledged
+      if (ratchet.nr > 53 || result.ratchetCreated || result.ratchetReplaced) {
+        await sendEmptyOmemoMessageImpl(
+          await _encryptToJids(
+            [stanza.bareSenderJid],
+            null,
+          ),
+          stanza.bareSenderJid,
+        );
+      }
+
+      // Ratchet is acked
+      await _leaveRatchetCriticalSection(stanza.bareSenderJid);
+      return DecryptionResult(
+        result.payload,
+        null,
+      );
+    } else {
+      // Ratchet is not acked.
+      // Mark as acked and send an empty OMEMO message.
+      await ratchetAcknowledged(
+        stanza.bareSenderJid,
+        stanza.senderDeviceId,
+        enterCriticalSection: false,
+      );
+      await sendEmptyOmemoMessageImpl(
+        await _encryptToJids(
+          [stanza.bareSenderJid],
+          null,
+        ),
+        stanza.bareSenderJid,
+      );
+
+      await _leaveRatchetCriticalSection(stanza.bareSenderJid);
+      return DecryptionResult(
+        result.payload,
+        null,
+      );
+    }
+  }
+
+  /// Call when sending out an encrypted stanza. Will handle everything and
+  /// encrypt it.
+  Future<EncryptionResult> onOutgoingStanza(OmemoOutgoingStanza stanza) async {
+    _log.finest('Waiting to enter critical section');
+    await _enterRatchetCriticalSection(stanza.recipientJids.first);
+    _log.finest('Entered critical section');
+
+    final result = _encryptToJids(
+      stanza.recipientJids,
+      stanza.payload,
+    );
+
+    await _leaveRatchetCriticalSection(stanza.recipientJids.first);
+
+    return result;
+  }
+
+  // Sends a hearbeat message as specified by XEP-0384 to [jid].
+  Future<void> sendOmemoHeartbeat(String jid) async {
+    // TODO(Unknown): Include some error handling
+    final result = await _encryptToJids(
+      [jid],
+      null,
+    );
+    await sendEmptyOmemoMessageImpl(result, jid);
+  }
+
+  /// Mark the ratchet for device [deviceId] from [jid] as acked.
+  Future<void> ratchetAcknowledged(
+    String jid,
+    int deviceId, {
+    bool enterCriticalSection = true,
+  }) async {
+    if (enterCriticalSection) await _enterRatchetCriticalSection(jid);
+
+    final key = RatchetMapKey(jid, deviceId);
+    if (_ratchetMap.containsKey(key)) {
+      final ratchet = _ratchetMap[key]!..acknowledged = true;
+
+      // Commit it
+      _eventStreamController
+          .add(RatchetModifiedEvent(jid, deviceId, ratchet, false, false));
+    } else {
+      _log.severe(
+        'Attempted to acknowledge ratchet ${key.toJsonKey()}, even though it does not exist',
+      );
+    }
+
+    if (enterCriticalSection) await _leaveRatchetCriticalSection(jid);
+  }
+
+  /// Generates an entirely new device. May be useful when the user wants to reset their cryptographic
+  /// identity. Triggers an event to commit it to storage.
+  Future<void> regenerateDevice() async {
+    await _deviceLock.synchronized(() async {
+      _device = await OmemoDevice.generateNewDevice(_device.jid);
+
+      // Commit it
+      _eventStreamController.add(DeviceModifiedEvent(_device));
+    });
+  }
+
+  /// Returns the device used for encryption and decryption.
+  Future<OmemoDevice> getDevice() => _deviceLock.synchronized(() => _device);
+
+  /// Returns the id of the device used for encryption and decryption.
+  Future<int> getDeviceId() async => (await getDevice()).id;
+
+  /// Directly aquire the current device as a OMEMO device bundle.
+  Future<OmemoBundle> getDeviceBundle() async => (await getDevice()).toBundle();
+
+  /// Directly aquire the current device's fingerprint.
+  Future<String> getDeviceFingerprint() async =>
+      (await getDevice()).getFingerprint();
+
+  /// Returns the fingerprints for all devices of [jid] that we have a session with.
+  /// If there are not sessions with [jid], then returns null.
+  Future<List<DeviceFingerprint>?> getFingerprintsForJid(String jid) async {
+    if (!_deviceList.containsKey(jid)) return null;
+
+    await _enterRatchetCriticalSection(jid);
+
+    final fingerprintKeys = _deviceList[jid]!
+        .map((id) => RatchetMapKey(jid, id))
+        .where((key) => _ratchetMap.containsKey(key));
+
+    final fingerprints = List<DeviceFingerprint>.empty(growable: true);
+    for (final key in fingerprintKeys) {
+      final curveKey = await _ratchetMap[key]!.ik.toCurve25519();
+      fingerprints.add(
+        DeviceFingerprint(
+          key.deviceId,
+          HEX.encode(await curveKey.getBytes()),
+        ),
+      );
+    }
+
+    await _leaveRatchetCriticalSection(jid);
+    return fingerprints;
+  }
+
+  /// Ensures that the device list is fetched again on the next message sending.
+  void onNewConnection() {
+    _deviceListRequested.clear();
+    _subscriptionMap.clear();
+  }
+
+  /// Sets the device list for [jid] to [devices]. Triggers a DeviceListModifiedEvent.
+  void onDeviceListUpdate(String jid, List<int> devices) {
+    _deviceList[jid] = devices;
+    _deviceListRequested[jid] = true;
+
+    // Trigger an event
+    _eventStreamController.add(DeviceListModifiedEvent(_deviceList));
+  }
+
+  void initialize(
+    Map<RatchetMapKey, OmemoDoubleRatchet> ratchetMap,
+    Map<String, List<int>> deviceList,
+  ) {
+    _deviceList = deviceList;
+    _ratchetMap = ratchetMap;
+  }
+
+  /// Removes all ratchets for JID [jid]. This also removes all trust decisions for
+  /// [jid] from the trust manager. This function triggers a RatchetRemovedEvent for
+  /// every removed ratchet and a DeviceListModifiedEvent afterwards. Behaviour for
+  /// the trust manager is dependent on its implementation.
+  Future<void> removeAllRatchets(String jid) async {
+    await _enterRatchetCriticalSection(jid);
+
+    for (final deviceId in _deviceList[jid]!) {
+      // Remove the ratchet and commit it
+      _ratchetMap.remove(RatchetMapKey(jid, deviceId));
+      _eventStreamController.add(RatchetRemovedEvent(jid, deviceId));
+    }
+
+    // Remove the devices from the device list cache and commit it
+    _deviceList.remove(jid);
+    _deviceListRequested.remove(jid);
+    _eventStreamController.add(DeviceListModifiedEvent(_deviceList));
+
+    // Remove trust decisions
+    await _trustManager.removeTrustDecisionsForJid(jid);
+
+    await _leaveRatchetCriticalSection(jid);
+  }
+
+  /// Replaces the internal device with [newDevice]. Does not trigger an event.
+  Future<void> replaceDevice(OmemoDevice newDevice) async {
+    await _deviceLock.synchronized(() {
+      _device = newDevice;
+    });
+  }
+}

lib/src/omemo/ratchet_map_key.dart

@@ -2,14 +2,30 @@ import 'package:meta/meta.dart';
 
 @immutable
 class RatchetMapKey {
-
   const RatchetMapKey(this.jid, this.deviceId);
+
+  factory RatchetMapKey.fromJsonKey(String key) {
+    final parts = key.split(':');
+    final deviceId = int.parse(parts.first);
+
+    return RatchetMapKey(
+      parts.sublist(1).join(':'),
+      deviceId,
+    );
+  }
+
   final String jid;
   final int deviceId;
 
+  String toJsonKey() {
+    return '$deviceId:$jid';
+  }
+
   @override
   bool operator ==(Object other) {
-    return other is RatchetMapKey && jid == other.jid && deviceId == other.deviceId;
+    return other is RatchetMapKey &&
+        jid == other.jid &&
+        deviceId == other.deviceId;
   }
 
   @override

lib/src/omemo/sessionmanager.dart

@@ -1,556 +0,0 @@
-import 'dart:async';
-import 'dart:convert';
-import 'package:collection/collection.dart';
-import 'package:cryptography/cryptography.dart';
-import 'package:hex/hex.dart';
-import 'package:meta/meta.dart';
-import 'package:omemo_dart/src/crypto.dart';
-import 'package:omemo_dart/src/double_ratchet/double_ratchet.dart';
-import 'package:omemo_dart/src/errors.dart';
-import 'package:omemo_dart/src/helpers.dart';
-import 'package:omemo_dart/src/keys.dart';
-import 'package:omemo_dart/src/omemo/bundle.dart';
-import 'package:omemo_dart/src/omemo/device.dart';
-import 'package:omemo_dart/src/omemo/encrypted_key.dart';
-import 'package:omemo_dart/src/omemo/encryption_result.dart';
-import 'package:omemo_dart/src/omemo/events.dart';
-import 'package:omemo_dart/src/omemo/fingerprint.dart';
-import 'package:omemo_dart/src/omemo/ratchet_map_key.dart';
-import 'package:omemo_dart/src/protobuf/omemo_authenticated_message.dart';
-import 'package:omemo_dart/src/protobuf/omemo_key_exchange.dart';
-import 'package:omemo_dart/src/protobuf/omemo_message.dart';
-import 'package:omemo_dart/src/trust/base.dart';
-import 'package:omemo_dart/src/x3dh/x3dh.dart';
-import 'package:synchronized/synchronized.dart';
-
-/// The info used for when encrypting the AES key for the actual payload.
-const omemoPayloadInfoString = 'OMEMO Payload';
-
-class OmemoSessionManager {
-
-  OmemoSessionManager(this._device, this._deviceMap, this._ratchetMap, this._trustManager)
-    : _lock = Lock(),
-      _deviceLock = Lock(),
-      _eventStreamController = StreamController<OmemoEvent>.broadcast();
-
-  /// Deserialise the OmemoSessionManager from JSON data [data].
-  factory OmemoSessionManager.fromJson(Map<String, dynamic> data, TrustManager trustManager) {
-    final ratchetMap = <RatchetMapKey, OmemoDoubleRatchet>{};
-    for (final rawRatchet in data['sessions']! as List<Map<String, dynamic>>) {
-      final key = RatchetMapKey(rawRatchet['jid']! as String, rawRatchet['deviceId']! as int);
-      final ratchet = OmemoDoubleRatchet.fromJson(rawRatchet['ratchet']! as Map<String, dynamic>);
-      ratchetMap[key] = ratchet;
-    }
-
-    return OmemoSessionManager(
-      Device.fromJson(data['device']! as Map<String, dynamic>),
-      data['devices']! as Map<String, List<int>>,
-      ratchetMap,
-      trustManager,
-    );
-  }
-
-  /// Deserialise the OmemoSessionManager from JSON data [data] that does not contain
-  /// the ratchet sessions.
-  factory OmemoSessionManager.fromJsonWithoutSessions(Map<String, dynamic> data, Map<RatchetMapKey, OmemoDoubleRatchet> ratchetMap, TrustManager trustManager) {
-    return OmemoSessionManager(
-      Device.fromJson(data['device']! as Map<String, dynamic>),
-      data['devices']! as Map<String, List<int>>,
-      ratchetMap,
-      trustManager,
-    );
-  }
-  
-  /// Generate a new cryptographic identity.
-  static Future<OmemoSessionManager> generateNewIdentity(String jid, TrustManager trustManager, { int opkAmount = 100 }) async {
-    assert(opkAmount > 0, 'opkAmount must be bigger than 0.');
-    final device = await Device.generateNewDevice(jid, opkAmount: opkAmount);
-
-    return OmemoSessionManager(device, {}, {}, trustManager);
-  }
-  
-  /// Lock for _ratchetMap and _bundleMap
-  final Lock _lock;
-
-  /// Mapping of the Device Id to its OMEMO session
-  final Map<RatchetMapKey, OmemoDoubleRatchet> _ratchetMap;
-
-  /// Mapping of a bare Jid to its Device Ids
-  final Map<String, List<int>> _deviceMap;
-
-  /// The event bus of the session manager
-  final StreamController<OmemoEvent> _eventStreamController;
-  
-  /// Our own keys...
-  // ignore: prefer_final_fields
-  Device _device;
-  /// and its lock
-  final Lock _deviceLock;
-
-  /// The trust manager
-  final TrustManager _trustManager;
-  TrustManager get trustManager => _trustManager;
-  
-  /// A stream that receives events regarding the session
-  Stream<OmemoEvent> get eventStream => _eventStreamController.stream;
-
-  /// Returns our own device.
-  Future<Device> getDevice() async {
-    Device? dev;
-    await _deviceLock.synchronized(() async {
-      dev = _device;
-    });
-
-    return dev!;
-  }
-
-  /// Returns the id attribute of our own device. This is just a short-hand for
-  /// ```await (session.getDevice()).id```.
-  Future<int> getDeviceId() async {
-    return _deviceLock.synchronized(() => _device.id);
-  }
-
-  /// Returns the device as an OmemoBundle. This is just a short-hand for
-  /// ```await (await session.getDevice()).toBundle()```.
-  Future<OmemoBundle> getDeviceBundle() async {
-    return _deviceLock.synchronized(() async => _device.toBundle());
-  }
-  
-  /// Add a session [ratchet] with the [deviceId] to the internal tracking state.
-  Future<void> _addSession(String jid, int deviceId, OmemoDoubleRatchet ratchet) async {
-    await _lock.synchronized(() async {
-      // Add the bundle Id
-      if (!_deviceMap.containsKey(jid)) {
-        _deviceMap[jid] = [deviceId];
-
-        // Commit the device map
-        _eventStreamController.add(DeviceMapModifiedEvent(_deviceMap));
-      } else {
-        // Prevent having the same device multiple times in the list
-        if (!_deviceMap[jid]!.contains(deviceId)) {
-          _deviceMap[jid]!.add(deviceId);
-
-          // Commit the device map
-          _eventStreamController.add(DeviceMapModifiedEvent(_deviceMap));
-        }
-      }
-
-      // Add the ratchet session
-      final key = RatchetMapKey(jid, deviceId);
-      _ratchetMap[key] = ratchet;
-
-      // Commit the ratchet
-      _eventStreamController.add(RatchetModifiedEvent(jid, deviceId, ratchet));
-    });
-  }
-
-  /// Create a ratchet session initiated by Alice to the user with Jid [jid] and the device
-  /// [deviceId] from the bundle [bundle].
-  @visibleForTesting
-  Future<OmemoKeyExchange> addSessionFromBundle(String jid, int deviceId, OmemoBundle bundle) async {
-    final device = await getDevice();
-    final kexResult = await x3dhFromBundle(
-      bundle,
-      device.ik,
-    );
-    final ratchet = await OmemoDoubleRatchet.initiateNewSession(
-      bundle.spk,
-      bundle.ik,
-      kexResult.sk,
-      kexResult.ad,
-    );
-
-    await _trustManager.onNewSession(jid, deviceId);
-    await _addSession(jid, deviceId, ratchet);
-
-    return OmemoKeyExchange()
-      ..pkId = kexResult.opkId
-      ..spkId = bundle.spkId
-      ..ik = await device.ik.pk.getBytes()
-      ..ek = await kexResult.ek.pk.getBytes();
-  }
-
-  /// Build a new session with the user at [jid] with the device [deviceId] using data
-  /// from the key exchange [kex]. In case [kex] contains an unknown Signed Prekey
-  /// identifier an UnknownSignedPrekeyException will be thrown.
-  Future<void> _addSessionFromKeyExchange(String jid, int deviceId, OmemoKeyExchange kex) async {
-    // Pick the correct SPK
-    final device = await getDevice();
-    OmemoKeyPair? spk;
-    if (kex.spkId == device.spkId) {
-      spk = device.spk;
-    } else if (kex.spkId == device.oldSpkId) {
-      spk = device.oldSpk;
-    } else {
-      throw UnknownSignedPrekeyException();
-    }
-
-    assert(spk != null, 'The used SPK must be found');
-    
-    final kexResult = await x3dhFromInitialMessage(
-      X3DHMessage(
-        OmemoPublicKey.fromBytes(kex.ik!, KeyPairType.ed25519),
-        OmemoPublicKey.fromBytes(kex.ek!, KeyPairType.x25519),
-        kex.pkId!,
-      ),
-      spk!,
-      device.opks.values.elementAt(kex.pkId!),
-      device.ik,
-    );
-    final ratchet = await OmemoDoubleRatchet.acceptNewSession(
-      spk,
-      OmemoPublicKey.fromBytes(kex.ik!, KeyPairType.ed25519),
-      kexResult.sk,
-      kexResult.ad,
-    );
-
-    await _trustManager.onNewSession(jid, deviceId);
-    await _addSession(jid, deviceId, ratchet);
-  }
-
-  /// Like [encryptToJids] but only for one Jid [jid].
-  Future<EncryptionResult> encryptToJid(String jid, String? plaintext, { List<OmemoBundle>? newSessions }) {
-    return encryptToJids([jid], plaintext, newSessions: newSessions);
-  }
-  
-  /// Encrypt the key [plaintext] for all known bundles of the Jids in [jids]. Returns a
-  /// map that maps the device Id to the ciphertext of [plaintext].
-  ///
-  /// If [plaintext] is null, then the result will be an empty OMEMO message, i.e. one that
-  /// does not contain a <payload /> element. This means that the ciphertext attribute of
-  /// the result will be null as well.
-  Future<EncryptionResult> encryptToJids(List<String> jids, String? plaintext, { List<OmemoBundle>? newSessions }) async {
-    final encryptedKeys = List<EncryptedKey>.empty(growable: true);
-
-    var ciphertext = const <int>[];
-    var keyPayload = const <int>[];
-    if (plaintext != null) {
-      // Generate the key and encrypt the plaintext
-      final key = generateRandomBytes(32);
-      final keys = await deriveEncryptionKeys(key, omemoPayloadInfoString);
-      ciphertext = await aes256CbcEncrypt(
-        utf8.encode(plaintext),
-        keys.encryptionKey,
-        keys.iv,
-      );
-      final hmac = await truncatedHmac(ciphertext, keys.authenticationKey);
-      keyPayload = concat([key, hmac]);
-    } else {
-      keyPayload = List<int>.filled(32, 0x0);
-    }
-
-    final kex = <int, OmemoKeyExchange>{};
-    if (newSessions != null) {
-      for (final newSession in newSessions) {
-        kex[newSession.id] = await addSessionFromBundle(newSession.jid, newSession.id, newSession);
-      }
-    }
-    
-    await _lock.synchronized(() async {
-      // We assume that the user already checked if the session exists
-      for (final jid in jids) {
-        for (final deviceId in _deviceMap[jid]!) {
-          // Empty OMEMO messages are allowed to bypass trust
-          if (plaintext != null) {
-            // Only encrypt to devices that are trusted
-            if (!(await _trustManager.isTrusted(jid, deviceId))) continue;
-          }
-
-          final ratchetKey = RatchetMapKey(jid, deviceId);
-          final ratchet = _ratchetMap[ratchetKey]!;
-          final ciphertext = (await ratchet.ratchetEncrypt(keyPayload)).ciphertext;
-
-          // Commit the ratchet
-          _eventStreamController.add(RatchetModifiedEvent(jid, deviceId, ratchet));
-          
-          if (kex.isNotEmpty && kex.containsKey(deviceId)) {
-            final k = kex[deviceId]!
-              ..message = OmemoAuthenticatedMessage.fromBuffer(ciphertext);
-            encryptedKeys.add(
-              EncryptedKey(
-                jid,
-                deviceId,
-                base64.encode(k.writeToBuffer()),
-                true,
-              ),
-            );
-          } else {
-            encryptedKeys.add(
-              EncryptedKey(
-                jid,
-                deviceId,
-                base64.encode(ciphertext),
-                false,
-              ),
-            );
-          }
-        }
-      }
-    });
-
-    return EncryptionResult(
-      plaintext != null ? ciphertext : null,
-      encryptedKeys,
-    );
-  }
-
-  /// Attempt to decrypt [ciphertext]. [keys] refers to the <key /> elements inside the
-  /// <keys /> element with a "jid" attribute matching our own. [senderJid] refers to the
-  /// bare Jid of the sender. [senderDeviceId] refers to the "sid" attribute of the
-  /// <encrypted /> element.
-  ///
-  /// If the received message is an empty OMEMO message, i.e. there is no <payload />
-  /// element, then [ciphertext] must be set to null. In this case, this function
-  /// will return null as there is no message to be decrypted. This, however, is used
-  /// to set up sessions or advance the ratchets.
-  Future<String?> decryptMessage(List<int>? ciphertext, String senderJid, int senderDeviceId, List<EncryptedKey> keys) async {
-    // Try to find a session we can decrypt with.
-    var device = await getDevice();
-    final rawKey = keys.firstWhereOrNull((key) => key.rid == device.id);
-    if (rawKey == null) {
-      throw NotEncryptedForDeviceException();
-    }
-
-    final decodedRawKey = base64.decode(rawKey.value);
-    OmemoAuthenticatedMessage authMessage;
-    if (rawKey.kex) {
-      // TODO(PapaTutuWawa): Only do this when we should
-      final kex = OmemoKeyExchange.fromBuffer(decodedRawKey);
-      await _addSessionFromKeyExchange(
-        senderJid,
-        senderDeviceId,
-        kex,
-      );
-
-      authMessage = kex.message!;
-
-      // Replace the OPK
-      await _deviceLock.synchronized(() async {
-        device = await device.replaceOnetimePrekey(kex.pkId!);
-
-        // Commit the device
-        _eventStreamController.add(DeviceModifiedEvent(device));
-      });
-    } else {
-      authMessage = OmemoAuthenticatedMessage.fromBuffer(decodedRawKey);
-    }
-    
-    final devices = _deviceMap[senderJid];
-    if (devices == null) {
-      throw NoDecryptionKeyException();
-    }
-    if (!devices.contains(senderDeviceId)) {
-      throw NoDecryptionKeyException();
-    }
-
-    final message = OmemoMessage.fromBuffer(authMessage.message!);
-    final ratchetKey = RatchetMapKey(senderJid, senderDeviceId);
-    List<int>? keyAndHmac;
-    await _lock.synchronized(() async {
-      final ratchet = _ratchetMap[ratchetKey]!;
-      if (rawKey.kex) {
-        keyAndHmac = await ratchet.ratchetDecrypt(message, authMessage.writeToBuffer());
-      } else {
-        keyAndHmac = await ratchet.ratchetDecrypt(message, decodedRawKey);
-      }
-
-      // Commit the ratchet
-      _eventStreamController.add(RatchetModifiedEvent(senderJid, senderDeviceId, ratchet));
-    });
-
-    // Empty OMEMO messages should just have the key decrypted and/or session set up.
-    if (ciphertext == null) {
-      return null;
-    }
-    
-    final key = keyAndHmac!.sublist(0, 32);
-    final hmac = keyAndHmac!.sublist(32, 48);
-    final derivedKeys = await deriveEncryptionKeys(key, omemoPayloadInfoString);
-
-    final computedHmac = await truncatedHmac(ciphertext, derivedKeys.authenticationKey);
-    if (!listsEqual(hmac, computedHmac)) {
-      throw InvalidMessageHMACException();
-    }
-    
-    final plaintext = await aes256CbcDecrypt(ciphertext, derivedKeys.encryptionKey, derivedKeys.iv);
-    return utf8.decode(plaintext);
-  }
-
-  /// Returns the list of hex-encoded fingerprints we have for sessions with [jid].
-  Future<List<DeviceFingerprint>> getHexFingerprintsForJid(String jid) async {
-    final fingerprints = List<DeviceFingerprint>.empty(growable: true);
-
-    await _lock.synchronized(() async {
-      // Get devices for jid
-      final devices = _deviceMap[jid]!;
-
-      for (final deviceId in devices) {
-        final ratchet = _ratchetMap[RatchetMapKey(jid, deviceId)]!;
-
-        fingerprints.add(
-          DeviceFingerprint(
-            deviceId,
-            HEX.encode(await ratchet.ik.getBytes()),
-          ),
-        );
-      }
-    });
-
-    return fingerprints;
-  }
-
-  /// Replaces the Signed Prekey and its signature in our own device bundle. Triggers
-  /// a DeviceModifiedEvent when done.
-  /// See https://xmpp.org/extensions/xep-0384.html#protocol-key_exchange under the point
-  /// "signed PreKey rotation period" for recommendations.
-  Future<void> rotateSignedPrekey() async {
-    await _deviceLock.synchronized(() async {
-      _device = await _device.replaceSignedPrekey();
-
-      // Commit the new device
-      _eventStreamController.add(DeviceModifiedEvent(_device));
-    });
-  }
-
-  /// Returns the device map, i.e. the mapping of bare Jid to its device identifiers
-  /// we have built sessions with.
-  Future<Map<String, List<int>>> getDeviceMap() async {
-    Map<String, List<int>>? map;
-
-    await _lock.synchronized(() async {
-      map = _deviceMap;
-    });
-
-    return map!;
-  }
-
-  /// Removes the ratchet identified by [jid] and [deviceId] from the session manager.
-  /// Also triggers events for commiting the new device map to storage and removing
-  /// the old ratchet.
-  Future<void> removeRatchet(String jid, int deviceId) async {
-    await _lock.synchronized(() async {
-      // Remove the ratchet
-      _ratchetMap.remove(RatchetMapKey(jid, deviceId));
-      // Commit it
-      _eventStreamController.add(RatchetRemovedEvent(jid, deviceId));
-
-      // Remove the device from jid
-      _deviceMap[jid]!.remove(deviceId);
-      if (_deviceMap[jid]!.isEmpty) {
-        _deviceMap.remove(jid);
-      }
-      // Commit it
-      _eventStreamController.add(DeviceMapModifiedEvent(_deviceMap));
-    });
-  }
-
-  /// Returns the list of device identifiers belonging to [jid] that are yet unacked, i.e.
-  /// we have not yet received an empty OMEMO message from.
-  Future<List<int>> getUnacknowledgedRatchets(String jid) async {
-    final ret = List<int>.empty(growable: true);
-
-    await _lock.synchronized(() async {
-      final devices = _deviceMap[jid]!;
-      for (final device in devices) {
-        final ratchet = _ratchetMap[RatchetMapKey(jid, device)]!;
-        if (!ratchet.acknowledged) ret.add(device);
-      }
-    });
-
-    return ret;
-  }
-
-  /// Mark the ratchet for device [deviceId] from [jid] as acked.
-  Future<void> ratchetAcknowledged(String jid, int deviceId) async {
-    await _lock.synchronized(() async {
-      final ratchet = _ratchetMap[RatchetMapKey(jid, deviceId)]!
-        ..acknowledged = true;
-
-      // Commit it
-      _eventStreamController.add(RatchetModifiedEvent(jid, deviceId, ratchet));
-    });
-  }
-
-  /// Generates an entirely new device. May be useful when the user wants to reset their cryptographic
-  /// identity. Triggers an event to commit it to storage.
-  Future<void> regenerateDevice({ int opkAmount = 100 }) async {
-    await _deviceLock.synchronized(() async {
-      _device = await Device.generateNewDevice(_device.jid, opkAmount: opkAmount);
-
-      // Commit it
-      _eventStreamController.add(DeviceModifiedEvent(_device));
-    });
-  }
-
-  /// Make our device have a new identifier. Only useful before publishing it as a bundle
-  /// to make sure that our device has a id that is account unique.
-  Future<void> regenerateDeviceId() async {
-    await _deviceLock.synchronized(() async {
-      _device = _device.withNewId();
-
-      // Commit it
-      _eventStreamController.add(DeviceModifiedEvent(_device));
-    });
-  }
-  
-  @visibleForTesting
-  OmemoDoubleRatchet getRatchet(String jid, int deviceId) => _ratchetMap[RatchetMapKey(jid, deviceId)]!;
-
-  @visibleForTesting
-  Map<RatchetMapKey, OmemoDoubleRatchet> getRatchetMap() => _ratchetMap;
-
-  /// Serialise the entire session manager into a JSON object.
-  Future<Map<String, dynamic>> toJson() async {
-    /*
-    {
-      'devices': {
-        'alice@...': [1, 2, ...],
-        'bob@...': [1],
-        ...
-      },
-      'device': { ... },
-      'sessions': [
-        {
-          'jid': 'alice@...',
-          'deviceId': 1,
-          'ratchet': { ... },
-        },
-        ...
-      ],
-    }
-    */
-
-    final sessions = List<Map<String, dynamic>>.empty(growable: true);
-    for (final entry in _ratchetMap.entries) {
-      sessions.add({
-        'jid': entry.key.jid,
-        'deviceId': entry.key.deviceId,
-        'ratchet': await entry.value.toJson(),
-      });
-    }
-    return {
-      'devices': _deviceMap,
-      'device': await (await getDevice()).toJson(),
-      'sessions': sessions,
-    };
-  }
-
-  /// Serialise the entire session manager into a JSON object.
-  Future<Map<String, dynamic>> toJsonWithoutSessions() async {
-    /*
-    {
-      'devices': {
-        'alice@...': [1, 2, ...],
-        'bob@...': [1],
-        ...
-      },
-      'device': { ... },
-    }
-    */
-
-    return {
-      'devices': _deviceMap,
-      'device': await (await getDevice()).toJson(),
-    };
-  }
-}

lib/src/omemo/stanza.dart

@@ -0,0 +1,41 @@
+import 'package:omemo_dart/src/omemo/encrypted_key.dart';
+
+/// Describes a stanza that was received by the underlying XMPP library.
+class OmemoIncomingStanza {
+  const OmemoIncomingStanza(
+    this.bareSenderJid,
+    this.senderDeviceId,
+    this.timestamp,
+    this.keys,
+    this.payload,
+  );
+
+  /// The bare JID of the sender of the stanza.
+  final String bareSenderJid;
+
+  /// The device ID of the sender.
+  final int senderDeviceId;
+
+  /// The timestamp when the stanza was received.
+  final int timestamp;
+
+  /// The included encrypted keys
+  final List<EncryptedKey> keys;
+
+  /// The string payload included in the <encrypted /> element.
+  final String? payload;
+}
+
+/// Describes a stanza that is to be sent out
+class OmemoOutgoingStanza {
+  const OmemoOutgoingStanza(
+    this.recipientJids,
+    this.payload,
+  );
+
+  /// The JIDs the stanza will be sent to.
+  final List<String> recipientJids;
+
+  /// The serialised XML data that should be encrypted.
+  final String payload;
+}

lib/src/protobuf/omemo_authenticated_message.dart

@@ -2,7 +2,6 @@ import 'package:omemo_dart/src/helpers.dart';
 import 'package:omemo_dart/src/protobuf/protobuf.dart';
 
 class OmemoAuthenticatedMessage {
-
   OmemoAuthenticatedMessage();
 
   factory OmemoAuthenticatedMessage.fromBuffer(List<int> data) {

lib/src/protobuf/omemo_key_exchange.dart

@@ -3,7 +3,6 @@ import 'package:omemo_dart/src/protobuf/omemo_authenticated_message.dart';
 import 'package:omemo_dart/src/protobuf/protobuf.dart';
 
 class OmemoKeyExchange {
-
   OmemoKeyExchange();
 
   factory OmemoKeyExchange.fromBuffer(List<int> data) {

lib/src/protobuf/omemo_message.dart

@@ -2,7 +2,6 @@ import 'package:omemo_dart/src/helpers.dart';
 import 'package:omemo_dart/src/protobuf/protobuf.dart';
 
 class OmemoMessage {
-
   OmemoMessage();
 
   factory OmemoMessage.fromBuffer(List<int> data) {

lib/src/protobuf/protobuf.dart

@@ -13,7 +13,6 @@ int fieldId(int number, int type) {
 }
 
 class VarintDecode {
-
   const VarintDecode(this.n, this.length);
   final int n;
   final int length;
@@ -46,21 +45,18 @@ List<int> encodeVarint(int i) {
   assert(i >= 0, "Two's complement is not implemented");
   final ret = List<int>.empty(growable: true);
 
-  var j = 0;
+  // Thanks to https://github.com/hathibelagal-dev/LEB128 for the trick with toRadixString!
-  while (true) {
+  final numSevenBlocks = (i.toRadixString(2).length / 7).ceil();
+  for (var j = 0; j < numSevenBlocks; j++) {
     // The 7 LSB of the byte we're creating
     final x = (i & (lsb7Mask << j * 7)) >> j * 7;
-    // The next bits
-    final next = i & (lsb7Mask << (j + 1) * 7);
 
-    if (next == 0) {
+    if (j == numSevenBlocks - 1) {
       // If we were to shift further, we only get zero, so we're at the end
       ret.add(x);
-      break;
     } else {
       // We still have at least one bit more to go, so set the MSB to 1
       ret.add(x + msb);
-      j++;
     }
   }
 

lib/src/trust/always.dart

@@ -11,4 +11,16 @@ class AlwaysTrustingTrustManager extends TrustManager {
 
   @override
   Future<void> onNewSession(String jid, int deviceId) async {}
+
+  @override
+  Future<bool> isEnabled(String jid, int deviceId) async => true;
+
+  @override
+  Future<void> setEnabled(String jid, int deviceId, bool enabled) async {}
+
+  @override
+  Future<void> removeTrustDecisionsForJid(String jid) async {}
+
+  @override
+  Future<Map<String, dynamic>> toJson() async => <String, dynamic>{};
 }

lib/src/trust/base.dart

@@ -8,4 +8,18 @@ abstract class TrustManager {
   /// Called by the OmemoSessionManager when a new session has been built. Should set
   /// a default trust state to [jid]'s device with identifier [deviceId].
   Future<void> onNewSession(String jid, int deviceId);
+
+  /// Return true if the device with id [deviceId] of Jid [jid] should be used for encryption.
+  /// If not, return false.
+  Future<bool> isEnabled(String jid, int deviceId);
+
+  /// Mark the device with id [deviceId] of Jid [jid] as enabled if [enabled] is true or as disabled
+  /// if [enabled] is false.
+  Future<void> setEnabled(String jid, int deviceId, bool enabled);
+
+  /// Serialize the trust manager to JSON.
+  Future<Map<String, dynamic>> toJson();
+
+  /// Removes all trust decisions for [jid].
+  Future<void> removeTrustDecisionsForJid(String jid);
 }

lib/src/trust/btbv.dart

@@ -8,24 +8,59 @@ import 'package:synchronized/synchronized.dart';
 /// - blindTrust: The fingerprint is not verified using OOB means
 /// - verified: The fingerprint has been verified using OOB means
 enum BTBVTrustState {
-  notTrusted,
+  notTrusted, // = 1
-  blindTrust,
+  blindTrust, // = 2
-  verified,
+  verified, // = 3
+}
+
+int _trustToInt(BTBVTrustState state) {
+  switch (state) {
+    case BTBVTrustState.notTrusted:
+      return 1;
+    case BTBVTrustState.blindTrust:
+      return 2;
+    case BTBVTrustState.verified:
+      return 3;
+  }
+}
+
+BTBVTrustState _trustFromInt(int i) {
+  switch (i) {
+    case 1:
+      return BTBVTrustState.notTrusted;
+    case 2:
+      return BTBVTrustState.blindTrust;
+    case 3:
+      return BTBVTrustState.verified;
+    default:
+      return BTBVTrustState.notTrusted;
+  }
 }
 
 /// A TrustManager that implements the idea of Blind Trust Before Verification.
 /// See https://gultsch.de/trust.html for more details.
 abstract class BlindTrustBeforeVerificationTrustManager extends TrustManager {
-  BlindTrustBeforeVerificationTrustManager()
+  BlindTrustBeforeVerificationTrustManager({
-    : trustCache = {},
+    Map<RatchetMapKey, BTBVTrustState>? trustCache,
-      devices = {},
+    Map<RatchetMapKey, bool>? enablementCache,
+    Map<String, List<int>>? devices,
+  })  : trustCache = trustCache ?? {},
+        enablementCache = enablementCache ?? {},
+        devices = devices ?? {},
         _lock = Lock();
 
-  /// The cache for Mapping a RatchetMapKey to its trust state
+  /// The cache for mapping a RatchetMapKey to its trust state
+  @visibleForTesting
   @protected
   final Map<RatchetMapKey, BTBVTrustState> trustCache;
 
+  /// The cache for mapping a RatchetMapKey to whether it is enabled or not
+  @visibleForTesting
+  @protected
+  final Map<RatchetMapKey, bool> enablementCache;
+
   /// Mapping of Jids to their device identifiers
+  @visibleForTesting
   @protected
   final Map<String, List<int>> devices;
 
@@ -74,10 +109,13 @@ abstract class BlindTrustBeforeVerificationTrustManager extends TrustManager {
   @override
   Future<void> onNewSession(String jid, int deviceId) async {
     await _lock.synchronized(() async {
+      final key = RatchetMapKey(jid, deviceId);
       if (_hasAtLeastOneVerifiedDevice(jid)) {
-        trustCache[RatchetMapKey(jid, deviceId)] = BTBVTrustState.notTrusted;
+        trustCache[key] = BTBVTrustState.notTrusted;
+        enablementCache[key] = false;
       } else {
-        trustCache[RatchetMapKey(jid, deviceId)] = BTBVTrustState.blindTrust;
+        trustCache[key] = BTBVTrustState.blindTrust;
+        enablementCache[key] = true;
       }
 
       if (devices.containsKey(jid)) {
@@ -91,21 +129,28 @@ abstract class BlindTrustBeforeVerificationTrustManager extends TrustManager {
     });
   }
 
-  /// Returns a mapping from the device identifiers of [jid] to their trust state.
+  /// Returns a mapping from the device identifiers of [jid] to their trust state. If
+  /// there are no devices known for [jid], then an empty map is returned.
   Future<Map<int, BTBVTrustState>> getDevicesTrust(String jid) async {
+    return _lock.synchronized(() async {
       final map = <int, BTBVTrustState>{};
 
-    await _lock.synchronized(() async {
+      if (!devices.containsKey(jid)) return map;
+
       for (final deviceId in devices[jid]!) {
         map[deviceId] = trustCache[RatchetMapKey(jid, deviceId)]!;
       }
-    });
 
       return map;
+    });
   }
 
   /// Sets the trust of [jid]'s device with identifier [deviceId] to [state].
-  Future<void> setDeviceTrust(String jid, int deviceId, BTBVTrustState state) async {
+  Future<void> setDeviceTrust(
+    String jid,
+    int deviceId,
+    BTBVTrustState state,
+  ) async {
     await _lock.synchronized(() async {
       trustCache[RatchetMapKey(jid, deviceId)] = state;
 
@@ -114,18 +159,95 @@ abstract class BlindTrustBeforeVerificationTrustManager extends TrustManager {
     });
   }
 
+  @override
+  Future<bool> isEnabled(String jid, int deviceId) async {
+    return _lock.synchronized(() async {
+      final value = enablementCache[RatchetMapKey(jid, deviceId)];
+
+      if (value == null) return false;
+      return value;
+    });
+  }
+
+  @override
+  Future<void> setEnabled(String jid, int deviceId, bool enabled) async {
+    await _lock.synchronized(() async {
+      enablementCache[RatchetMapKey(jid, deviceId)] = enabled;
+    });
+
+    // Commit the state
+    await commitState();
+  }
+
+  @override
+  Future<Map<String, dynamic>> toJson() async {
+    return {
+      'devices': devices,
+      'trust': trustCache.map(
+        (key, value) => MapEntry(
+          key.toJsonKey(),
+          _trustToInt(value),
+        ),
+      ),
+      'enable':
+          enablementCache.map((key, value) => MapEntry(key.toJsonKey(), value)),
+    };
+  }
+
+  /// From a serialized version of a BTBV trust manager, extract the device list.
+  /// NOTE: This is needed as Dart cannot just cast a List<dynamic> to List<int> and so on.
+  static Map<String, List<int>> deviceListFromJson(Map<String, dynamic> json) {
+    return (json['devices']! as Map<String, dynamic>).map<String, List<int>>(
+      (key, value) => MapEntry(
+        key,
+        (value as List<dynamic>).map<int>((i) => i as int).toList(),
+      ),
+    );
+  }
+
+  /// From a serialized version of a BTBV trust manager, extract the trust cache.
+  /// NOTE: This is needed as Dart cannot just cast a List<dynamic> to List<int> and so on.
+  static Map<RatchetMapKey, BTBVTrustState> trustCacheFromJson(
+    Map<String, dynamic> json,
+  ) {
+    return (json['trust']! as Map<String, dynamic>)
+        .map<RatchetMapKey, BTBVTrustState>(
+      (key, value) => MapEntry(
+        RatchetMapKey.fromJsonKey(key),
+        _trustFromInt(value as int),
+      ),
+    );
+  }
+
+  /// From a serialized version of a BTBV trust manager, extract the enable cache.
+  /// NOTE: This is needed as Dart cannot just cast a List<dynamic> to List<int> and so on.
+  static Map<RatchetMapKey, bool> enableCacheFromJson(
+    Map<String, dynamic> json,
+  ) {
+    return (json['enable']! as Map<String, dynamic>).map<RatchetMapKey, bool>(
+      (key, value) => MapEntry(
+        RatchetMapKey.fromJsonKey(key),
+        value as bool,
+      ),
+    );
+  }
+
+  @override
+  Future<void> removeTrustDecisionsForJid(String jid) async {
+    await _lock.synchronized(() async {
+      devices.remove(jid);
+      await commitState();
+    });
+  }
+
   /// Called when the state of the trust manager has been changed. Allows the user to
   /// commit the trust state to persistent storage.
   @visibleForOverriding
   Future<void> commitState();
 
-  /// Called when the user wants to restore the state of the trust manager. The format
-  /// and actual storage mechanism is left to the user.
-  @visibleForOverriding
-  Future<void> loadState();
-  
   @visibleForTesting
-  BTBVTrustState getDeviceTrust(String jid, int deviceId) => trustCache[RatchetMapKey(jid, deviceId)]!;
+  BTBVTrustState getDeviceTrust(String jid, int deviceId) =>
+      trustCache[RatchetMapKey(jid, deviceId)]!;
 }
 
 /// A BTBV TrustManager that does not commit its state to persistent storage. Well suited
@@ -133,7 +255,4 @@ abstract class BlindTrustBeforeVerificationTrustManager extends TrustManager {
 class MemoryBTBVTrustManager extends BlindTrustBeforeVerificationTrustManager {
   @override
   Future<void> commitState() async {}
-
-  @override
-  Future<void> loadState() async {}
 }

lib/src/trust/never.dart

@@ -11,4 +11,16 @@ class NeverTrustingTrustManager extends TrustManager {
 
   @override
   Future<void> onNewSession(String jid, int deviceId) async {}
+
+  @override
+  Future<bool> isEnabled(String jid, int deviceId) async => true;
+
+  @override
+  Future<void> setEnabled(String jid, int deviceId, bool enabled) async {}
+
+  @override
+  Future<void> removeTrustDecisionsForJid(String jid) async {}
+
+  @override
+  Future<Map<String, dynamic>> toJson() async => <String, dynamic>{};
 }

lib/src/x3dh/x3dh.dart

@@ -12,7 +12,6 @@ const omemoX3DHInfoString = 'OMEMO X3DH';
 
 /// Performed by Alice
 class X3DHAliceResult {
-
   const X3DHAliceResult(this.ek, this.sk, this.opkId, this.ad);
   final OmemoKeyPair ek;
   final List<int> sk;
@@ -22,7 +21,6 @@ class X3DHAliceResult {
 
 /// Received by Bob
 class X3DHMessage {
-
   const X3DHMessage(this.ik, this.ek, this.opkId);
   final OmemoPublicKey ik;
   final OmemoPublicKey ek;
@@ -30,7 +28,6 @@ class X3DHMessage {
 }
 
 class X3DHBobResult {
-
   const X3DHBobResult(this.sk, this.ad);
   final List<int> sk;
   final List<int> ad;
@@ -39,7 +36,10 @@ class X3DHBobResult {
 /// Sign [message] using the keypair [keyPair]. Note that [keyPair] must be
 /// a Ed25519 keypair.
 Future<List<int>> sig(OmemoKeyPair keyPair, List<int> message) async {
-  assert(keyPair.type == KeyPairType.ed25519, 'Signature keypair must be Ed25519');
+  assert(
+    keyPair.type == KeyPairType.ed25519,
+    'Signature keypair must be Ed25519',
+  );
   final signature = await Ed25519().sign(
     message,
     keyPair: await keyPair.asKeyPair(),
@@ -70,7 +70,10 @@ Future<List<int>> kdf(List<int> km) async {
 
 /// Alice builds a session with Bob using his bundle [bundle] and Alice's identity key
 /// pair [ik].
-Future<X3DHAliceResult> x3dhFromBundle(OmemoBundle bundle, OmemoKeyPair ik) async {
+Future<X3DHAliceResult> x3dhFromBundle(
+  OmemoBundle bundle,
+  OmemoKeyPair ik,
+) async {
   // Check the signature first
   final signatureValue = await Ed25519().verify(
     await bundle.spk.getBytes(),
@@ -108,7 +111,12 @@ Future<X3DHAliceResult> x3dhFromBundle(OmemoBundle bundle, OmemoKeyPair ik) asyn
 
 /// Bob builds the X3DH shared secret from the inital message [msg], the SPK [spk], the
 /// OPK [opk] that was selected by Alice and our IK [ik]. Returns the shared secret.
-Future<X3DHBobResult> x3dhFromInitialMessage(X3DHMessage msg, OmemoKeyPair spk, OmemoKeyPair opk, OmemoKeyPair ik) async {
+Future<X3DHBobResult> x3dhFromInitialMessage(
+  X3DHMessage msg,
+  OmemoKeyPair spk,
+  OmemoKeyPair opk,
+  OmemoKeyPair ik,
+) async {
   final dh1 = await omemoDH(spk, msg.ik, 2);
   final dh2 = await omemoDH(ik, msg.ek, 1);
   final dh3 = await omemoDH(spk, msg.ek, 0);

pubspec.yaml

@@ -1,6 +1,6 @@
 name: omemo_dart
 description: An XMPP library independent OMEMO library
-version: 0.2.0
+version: 0.4.3
 homepage: https://github.com/PapaTutuWawa/omemo_dart
 publish_to: https://git.polynom.me/api/packages/PapaTutuWawa/pub
 
@@ -11,7 +11,8 @@ dependencies:
   collection: ^1.16.0
   cryptography: ^2.0.5
   hex: ^0.2.0
-  meta: ^1.8.0
+  logging: ^1.0.2
+  meta: ^1.7.0
   pinenacl: ^0.5.1
   synchronized: ^3.0.0+2
 

test/double_ratchet_test.dart

@@ -76,7 +76,6 @@ void main() {
 
     print('X3DH key exchange done');
 
-
     // Alice and Bob now share sk as a common secret and ad
     // Build a session
     final alicesRatchet = await OmemoDoubleRatchet.initiateNewSession(
@@ -84,12 +83,14 @@ void main() {
       ikBob.pk,
       resultAlice.sk,
       resultAlice.ad,
+      0,
     );
     final bobsRatchet = await OmemoDoubleRatchet.acceptNewSession(
       spkBob,
       ikAlice.pk,
       resultBob.sk,
       resultBob.ad,
+      0,
     );
 
     expect(alicesRatchet.sessionAd, bobsRatchet.sessionAd);
@@ -99,7 +100,8 @@ void main() {
 
       if (i.isEven) {
         // Alice encrypts a message
-        final aliceRatchetResult = await alicesRatchet.ratchetEncrypt(utf8.encode(messageText));
+        final aliceRatchetResult =
+            await alicesRatchet.ratchetEncrypt(utf8.encode(messageText));
         print('Alice sent the message');
 
         // Alice sends it to Bob
@@ -115,7 +117,8 @@ void main() {
         expect(utf8.encode(messageText), bobRatchetResult);
       } else {
         // Bob sends a message to Alice
-        final bobRatchetResult = await bobsRatchet.ratchetEncrypt(utf8.encode(messageText));
+        final bobRatchetResult =
+            await bobsRatchet.ratchetEncrypt(utf8.encode(messageText));
         print('Bob sent the message');
 
         // Bobs sends it to Alice

test/omemo_test.dart

@@ -1,9 +1,47 @@
+import 'package:logging/logging.dart';
 import 'package:omemo_dart/omemo_dart.dart';
 import 'package:omemo_dart/src/trust/always.dart';
 import 'package:omemo_dart/src/trust/never.dart';
 import 'package:test/test.dart';
 
 void main() {
+  Logger.root
+    ..level = Level.ALL
+    ..onRecord.listen((record) {
+      // ignore: avoid_print
+      print('${record.level.name}: ${record.message}');
+    });
+
+  test('Test replacing a onetime prekey', () async {
+    const aliceJid = 'alice@server.example';
+    final device = await OmemoDevice.generateNewDevice(aliceJid, opkAmount: 1);
+
+    final newDevice = await device.replaceOnetimePrekey(0);
+
+    expect(device.jid, newDevice.jid);
+    expect(device.id, newDevice.id);
+
+    var opksMatch = true;
+    if (newDevice.opks.length != device.opks.length) {
+      opksMatch = false;
+    } else {
+      for (final entry in device.opks.entries) {
+        final m = await newDevice.opks[entry.key]?.equals(entry.value) ?? false;
+        if (!m) opksMatch = false;
+      }
+    }
+
+    expect(opksMatch, true);
+    expect(await device.ik.equals(newDevice.ik), true);
+    expect(await device.spk.equals(newDevice.spk), true);
+
+    final oldSpkMatch = device.oldSpk != null
+        ? await device.oldSpk!.equals(newDevice.oldSpk!)
+        : newDevice.oldSpk == null;
+    expect(oldSpkMatch, true);
+    expect(listsEqual(device.spkSignature, newDevice.spkSignature), true);
+  });
+
   test('Test using OMEMO sessions with only one device per user', () async {
     const aliceJid = 'alice@server.example';
     const bobJid = 'bob@other.server.example';
@@ -27,7 +65,7 @@ void main() {
         deviceModified = true;
       } else if (event is RatchetModifiedEvent) {
         ratchetModified++;
-      } else if (event is DeviceMapModifiedEvent) {
+      } else if (event is DeviceListModifiedEvent) {
         deviceMapModified++;
       }
     });
@@ -52,6 +90,7 @@ void main() {
       aliceJid,
       await aliceSession.getDeviceId(),
       aliceMessage.encryptedKeys,
+      0,
     );
     expect(messagePlaintext, bobMessage);
     // The ratchet should be modified two times: Once for when the ratchet is created and
@@ -67,6 +106,12 @@ void main() {
       false,
     );
 
+    // Ratchets are acked
+    await aliceSession.ratchetAcknowledged(
+        bobJid, await bobSession.getDeviceId());
+    await bobSession.ratchetAcknowledged(
+        aliceJid, await aliceSession.getDeviceId());
+
     // Bob responds to Alice
     const bobResponseText = 'Oh, hello Alice!';
     final bobResponseMessage = await bobSession.encryptToJid(
@@ -83,11 +128,13 @@ void main() {
       bobJid,
       await bobSession.getDeviceId(),
       bobResponseMessage.encryptedKeys,
+      0,
     );
     expect(bobResponseText, aliceReceivedMessage);
   });
 
-  test('Test using OMEMO sessions with only two devices for the receiver', () async {
+  test('Test using OMEMO sessions with only two devices for the receiver',
+      () async {
     const aliceJid = 'alice@server.example';
     const bobJid = 'bob@other.server.example';
 
@@ -132,9 +179,16 @@ void main() {
       aliceJid,
       await aliceSession.getDeviceId(),
       aliceMessage.encryptedKeys,
+      0,
     );
     expect(messagePlaintext, bobMessage);
 
+    // Ratchets are acked
+    await aliceSession.ratchetAcknowledged(
+        bobJid, await bobSession.getDeviceId());
+    await bobSession.ratchetAcknowledged(
+        aliceJid, await aliceSession.getDeviceId());
+
     // Bob responds to Alice
     const bobResponseText = 'Oh, hello Alice!';
     final bobResponseMessage = await bobSession.encryptToJid(
@@ -151,6 +205,7 @@ void main() {
       bobJid,
       await bobSession.getDeviceId(),
       bobResponseMessage.encryptedKeys,
+      0,
     );
     expect(bobResponseText, aliceReceivedMessage);
 
@@ -207,6 +262,7 @@ void main() {
       aliceJid,
       await aliceSession1.getDeviceId(),
       aliceMessage.encryptedKeys,
+      0,
     );
     expect(messagePlaintext, bobMessage);
 
@@ -216,11 +272,12 @@ void main() {
       aliceJid,
       await aliceSession1.getDeviceId(),
       aliceMessage.encryptedKeys,
+      0,
     );
     expect(messagePlaintext, aliceMessage2);
   });
 
-  test('Test using sending empty OMEMO messages', () async {
+  test('Test sending empty OMEMO messages', () async {
     const aliceJid = 'alice@server.example';
     const bobJid = 'bob@other.server.example';
 
@@ -256,6 +313,7 @@ void main() {
       aliceJid,
       await aliceSession.getDeviceId(),
       aliceMessage.encryptedKeys,
+      0,
     );
     expect(bobMessage, null);
 
@@ -274,7 +332,7 @@ void main() {
 
     // Setup an event listener
     final oldDevice = await aliceSession.getDevice();
-    Device? newDevice;
+    OmemoDevice? newDevice;
     aliceSession.eventStream.listen((event) {
       if (event is DeviceModifiedEvent) {
         newDevice = event.device;
@@ -333,6 +391,7 @@ void main() {
       aliceJid,
       await aliceSession.getDeviceId(),
       aliceMessage.encryptedKeys,
+      0,
     );
     expect(messagePlaintext, bobMessage);
   });
@@ -399,8 +458,15 @@ void main() {
       aliceJid,
       await aliceSession.getDeviceId(),
       aliceMessage.encryptedKeys,
+      0,
     );
 
+    // Ratchets are acked
+    await aliceSession.ratchetAcknowledged(
+        bobJid, await bobSession.getDeviceId());
+    await bobSession.ratchetAcknowledged(
+        aliceJid, await aliceSession.getDeviceId());
+
     for (var i = 0; i < 100; i++) {
       final messageText = 'Test Message #$i';
       // Bob responds to Alice
@@ -418,6 +484,7 @@ void main() {
         bobJid,
         await bobSession.getDeviceId(),
         bobResponseMessage.encryptedKeys,
+        0,
       );
       expect(messageText, aliceReceivedMessage);
     }
@@ -537,9 +604,10 @@ void main() {
     // ...
 
     // Alice marks the ratchet as acknowledged
-    await aliceSession.ratchetAcknowledged(bobJid, await bobSession.getDeviceId());
+    await aliceSession.ratchetAcknowledged(
+        bobJid, await bobSession.getDeviceId());
     expect(
-      (await aliceSession.getUnacknowledgedRatchets(bobJid)).isEmpty,
+      (await aliceSession.getUnacknowledgedRatchets(bobJid))!.isEmpty,
       true,
     );
   });
@@ -572,6 +640,7 @@ void main() {
       aliceJid,
       await aliceSession.getDeviceId(),
       msg1.encryptedKeys,
+      0,
     );
     final aliceRatchet1 = aliceSession.getRatchet(
       bobJid,
@@ -596,6 +665,7 @@ void main() {
       aliceJid,
       await aliceSession.getDeviceId(),
       msg2.encryptedKeys,
+      getTimestamp(),
     );
     final aliceRatchet2 = aliceSession.getRatchet(
       bobJid,
@@ -614,4 +684,273 @@ void main() {
     expect(await aliceRatchet1.equals(aliceRatchet2), false);
     expect(await bobRatchet1.equals(bobRatchet2), false);
   });
+
+  test('Test resending key exchanges', () async {
+    const aliceJid = 'alice@server.example';
+    const bobJid = 'bob@other.server.example';
+    // Alice and Bob generate their sessions
+    final aliceSession = await OmemoSessionManager.generateNewIdentity(
+      aliceJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
+    final bobSession = await OmemoSessionManager.generateNewIdentity(
+      bobJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 2,
+    );
+
+    // Alice sends Bob a message
+    final msg1 = await aliceSession.encryptToJid(
+      bobJid,
+      'Hallo Welt',
+      newSessions: [
+        await bobSession.getDeviceBundle(),
+      ],
+    );
+    // The first message should be a kex message
+    expect(msg1.encryptedKeys.first.kex, true);
+
+    await bobSession.decryptMessage(
+      msg1.ciphertext,
+      aliceJid,
+      await aliceSession.getDeviceId(),
+      msg1.encryptedKeys,
+      0,
+    );
+
+    // Alice is impatient and immediately sends another message before the original one
+    // can be acknowledged by Bob
+    final msg2 = await aliceSession.encryptToJid(
+      bobJid,
+      "Why don't you answer?",
+    );
+    expect(msg2.encryptedKeys.first.kex, true);
+
+    await bobSession.decryptMessage(
+      msg2.ciphertext,
+      aliceJid,
+      await aliceSession.getDeviceId(),
+      msg2.encryptedKeys,
+      getTimestamp(),
+    );
+  });
+
+  test('Test receiving old messages including a KEX', () async {
+    const aliceJid = 'alice@server.example';
+    const bobJid = 'bob@other.server.example';
+    // Alice and Bob generate their sessions
+    final aliceSession = await OmemoSessionManager.generateNewIdentity(
+      aliceJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
+    final bobSession = await OmemoSessionManager.generateNewIdentity(
+      bobJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 2,
+    );
+
+    final bobsReceivedMessages = List<EncryptionResult>.empty(growable: true);
+    final bobsReceivedMessagesTimestamps = List<int>.empty(growable: true);
+
+    // Alice sends Bob a message
+    final msg1 = await aliceSession.encryptToJid(
+      bobJid,
+      'Hallo Welt',
+      newSessions: [
+        await bobSession.getDeviceBundle(),
+      ],
+    );
+    bobsReceivedMessages.add(msg1);
+    final t1 = getTimestamp();
+    bobsReceivedMessagesTimestamps.add(t1);
+
+    await bobSession.decryptMessage(
+      msg1.ciphertext,
+      aliceJid,
+      await aliceSession.getDeviceId(),
+      msg1.encryptedKeys,
+      t1,
+    );
+
+    // Ratchets are acked
+    await aliceSession.ratchetAcknowledged(
+        bobJid, await bobSession.getDeviceId());
+    await bobSession.ratchetAcknowledged(
+        aliceJid, await aliceSession.getDeviceId());
+
+    // Bob responds
+    final msg2 = await bobSession.encryptToJid(
+      aliceJid,
+      'Hello!',
+    );
+
+    await aliceSession.decryptMessage(
+      msg2.ciphertext,
+      bobJid,
+      await bobSession.getDeviceId(),
+      msg2.encryptedKeys,
+      getTimestamp(),
+    );
+
+    // Send some messages between the two
+    for (var i = 0; i < 100; i++) {
+      final msg = await aliceSession.encryptToJid(
+        bobJid,
+        'Hello $i',
+      );
+      bobsReceivedMessages.add(msg);
+      final t = getTimestamp();
+      bobsReceivedMessagesTimestamps.add(t);
+      final result = await bobSession.decryptMessage(
+        msg.ciphertext,
+        aliceJid,
+        await aliceSession.getDeviceId(),
+        msg.encryptedKeys,
+        t,
+      );
+
+      expect(result, 'Hello $i');
+    }
+
+    // Due to some issue with the transport protocol, the messages to Bob are received
+    // again.
+    final ratchetPreError = bobSession
+        .getRatchet(aliceJid, await aliceSession.getDeviceId())
+        .clone();
+    var invalidKex = 0;
+    var errorCounter = 0;
+    for (var i = 0; i < bobsReceivedMessages.length; i++) {
+      final msg = bobsReceivedMessages[i];
+      try {
+        await bobSession.decryptMessage(
+          msg.ciphertext,
+          aliceJid,
+          await aliceSession.getDeviceId(),
+          msg.encryptedKeys,
+          bobsReceivedMessagesTimestamps[i],
+        );
+        expect(true, false);
+      } on InvalidMessageHMACException catch (_) {
+        errorCounter++;
+      } on InvalidKeyExchangeException catch (_) {
+        invalidKex++;
+      }
+    }
+    final ratchetPostError = bobSession
+        .getRatchet(aliceJid, await aliceSession.getDeviceId())
+        .clone();
+
+    // The 100 messages including the initial KEX message
+    expect(invalidKex, 1);
+    expect(errorCounter, 100);
+    expect(await ratchetPreError.equals(ratchetPostError), true);
+
+    final msg3 = await aliceSession.encryptToJid(
+      bobJid,
+      'Are you okay?',
+    );
+    final result = await bobSession.decryptMessage(
+      msg3.ciphertext,
+      aliceJid,
+      await aliceSession.getDeviceId(),
+      msg3.encryptedKeys,
+      104,
+    );
+
+    expect(result, 'Are you okay?');
+  });
+
+  test("Test ignoring a new KEX when we haven't acket it yet", () async {
+    const aliceJid = 'alice@server.example';
+    const bobJid = 'bob@other.server.example';
+    // Alice and Bob generate their sessions
+    final aliceSession = await OmemoSessionManager.generateNewIdentity(
+      aliceJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
+    final bobSession = await OmemoSessionManager.generateNewIdentity(
+      bobJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
+
+    // Alice sends Bob a message
+    final msg1 = await aliceSession.encryptToJid(
+      bobJid,
+      'Hallo Welt',
+      newSessions: [
+        await bobSession.getDeviceBundle(),
+      ],
+    );
+    expect(msg1.encryptedKeys.first.kex, true);
+
+    await bobSession.decryptMessage(
+      msg1.ciphertext,
+      aliceJid,
+      await aliceSession.getDeviceId(),
+      msg1.encryptedKeys,
+      getTimestamp(),
+    );
+
+    // Alice sends another message before the ack can reach us
+    final msg2 = await aliceSession.encryptToJid(
+      bobJid,
+      'ANSWER ME!',
+    );
+    expect(msg2.encryptedKeys.first.kex, true);
+
+    await bobSession.decryptMessage(
+      msg2.ciphertext,
+      aliceJid,
+      await aliceSession.getDeviceId(),
+      msg2.encryptedKeys,
+      getTimestamp(),
+    );
+
+    // Now the acks reach us
+    await aliceSession.ratchetAcknowledged(
+        bobJid, await bobSession.getDeviceId());
+    await bobSession.ratchetAcknowledged(
+        aliceJid, await aliceSession.getDeviceId());
+
+    // Alice sends another message
+    final msg3 = await aliceSession.encryptToJid(
+      bobJid,
+      "You read the message, didn't you?",
+    );
+    expect(msg3.encryptedKeys.first.kex, false);
+
+    await bobSession.decryptMessage(
+      msg3.ciphertext,
+      aliceJid,
+      await aliceSession.getDeviceId(),
+      msg3.encryptedKeys,
+      getTimestamp(),
+    );
+
+    for (var i = 0; i < 100; i++) {
+      final messageText = 'Test Message #$i';
+      // Bob responds to Alice
+      final bobResponseMessage = await bobSession.encryptToJid(
+        aliceJid,
+        messageText,
+      );
+
+      // Bob sends the message to Alice
+      // ...
+
+      // Alice decrypts it
+      final aliceReceivedMessage = await aliceSession.decryptMessage(
+        bobResponseMessage.ciphertext,
+        bobJid,
+        await bobSession.getDeviceId(),
+        bobResponseMessage.encryptedKeys,
+        0,
+      );
+      expect(messageText, aliceReceivedMessage);
+    }
+  });
 }

test/protobuf_test.dart

@@ -48,6 +48,10 @@ void main() {
         <int>[172, 2],
       );
     });
+
+    test('Test some special cases', () {
+      expect(decodeVarint(encodeVarint(1042464893), 0).n, 1042464893);
+    });
   });
 
   group('OMEMOMessage', () {
@@ -165,10 +169,18 @@ void main() {
       expect(decoded.pkId, 698);
       expect(decoded.spkId, 245);
       expect(decoded.ik, <int>[1, 4, 6]);
-      expect(decoded.ek, <int>[4 ,6 ,7 , 80]);
+      expect(decoded.ek, <int>[4, 6, 7, 80]);
 
       expect(decoded.message!.mac, <int>[5, 6, 8, 0]);
       expect(decoded.message!.message, <int>[4, 5, 7, 3, 2]);
     });
+    test('Test decoding an issue', () {
+      /*
+      final data = 'CAAQfRogc2GwslU219dUkrMHNM4KdZRmuFnBTae+bQaJ+55IsAMiII7aZKj2sUpb6xR/3Ari7WZUmKFV0G6czUc4NMvjKDBaKnwKEM2ZpI8X3TgcxhxwENANnlsSaAgAEAAaICy8T9WPgLb7RdYd8/4JkrLF0RahEkC3ZaEfk5jw3dsLIkBMILzLyByweLgF4lCn0oNea+kbdrFr6rY7r/7WyI8hXEQz38QpnN+jyGGwC7Ga0dq70WuyqE7VpiFArQwqZh2G';
+      final kex = OmemoKeyExchange.fromBuffer(base64Decode(data));
+
+      expect(kex.spkId!, 1042464893);
+      */
+    });
   });
 }

test/serialisation_test.dart

@@ -1,7 +1,12 @@
+import 'dart:convert';
 import 'package:omemo_dart/omemo_dart.dart';
 import 'package:omemo_dart/src/trust/always.dart';
 import 'package:test/test.dart';
 
+Map<String, dynamic> jsonify(Map<String, dynamic> map) {
+  return jsonDecode(jsonEncode(map)) as Map<String, dynamic>;
+}
+
 void main() {
   test('Test serialising and deserialising the Device', () async {
     // Generate a random session
@@ -11,23 +16,25 @@ void main() {
       opkAmount: 1,
     );
     final oldDevice = await oldSession.getDevice();
-    final serialised = await oldDevice.toJson();
+    final serialised = jsonify(await oldDevice.toJson());
 
-    final newDevice = Device.fromJson(serialised);
+    final newDevice = OmemoDevice.fromJson(serialised);
     expect(await oldDevice.equals(newDevice), true);
   });
 
-  test('Test serialising and deserialising the Device after rotating the SPK', () async {
+  test('Test serialising and deserialising the Device after rotating the SPK',
+      () async {
     // Generate a random session
     final oldSession = await OmemoSessionManager.generateNewIdentity(
       'user@test.server',
       AlwaysTrustingTrustManager(),
       opkAmount: 1,
     );
-    final oldDevice = await (await oldSession.getDevice()).replaceSignedPrekey();
+    final oldDevice =
-    final serialised = await oldDevice.toJson();
+        await (await oldSession.getDevice()).replaceSignedPrekey();
+    final serialised = jsonify(await oldDevice.toJson());
 
-    final newDevice = Device.fromJson(serialised);
+    final newDevice = OmemoDevice.fromJson(serialised);
     expect(await oldDevice.equals(newDevice), true);
   });
 
@@ -57,9 +64,11 @@ void main() {
       aliceJid,
       await aliceSession.getDeviceId(),
       aliceMessage.encryptedKeys,
+      getTimestamp(),
     );
-    final aliceOld = aliceSession.getRatchet(bobJid, await bobSession.getDeviceId());
+    final aliceOld =
-    final aliceSerialised = await aliceOld.toJson();
+        aliceSession.getRatchet(bobJid, await bobSession.getDeviceId());
+    final aliceSerialised = jsonify(await aliceOld.toJson());
     final aliceNew = OmemoDoubleRatchet.fromJson(aliceSerialised);
 
     expect(await aliceOld.equals(aliceNew), true);
@@ -84,9 +93,11 @@ void main() {
     );
 
     // Serialise and deserialise
-    final serialised = await oldSession.toJson();
+    final serialised = jsonify(await oldSession.toJsonWithoutSessions());
-    final newSession = OmemoSessionManager.fromJson(
+    final newSession = OmemoSessionManager.fromJsonWithoutSessions(
       serialised,
+      // NOTE: At this point, we don't care about this attribute
+      {},
       AlwaysTrustingTrustManager(),
     );
 
@@ -94,14 +105,51 @@ void main() {
     final newDevice = await newSession.getDevice();
     expect(await oldDevice.equals(newDevice), true);
     expect(await oldSession.getDeviceMap(), await newSession.getDeviceMap());
+  });
 
-    expect(oldSession.getRatchetMap().length, newSession.getRatchetMap().length);
+  test('Test serializing and deserializing RatchetMapKey', () {
-    for (final session in oldSession.getRatchetMap().entries) {
+    const test1 = RatchetMapKey('user@example.org', 1234);
-      expect(newSession.getRatchetMap().containsKey(session.key), true);
+    final result1 = RatchetMapKey.fromJsonKey(test1.toJsonKey());
+    expect(result1.jid, test1.jid);
+    expect(result1.deviceId, test1.deviceId);
 
-      final oldRatchet = oldSession.getRatchetMap()[session.key]!;
+    const test2 = RatchetMapKey('user@example.org/hallo:welt', 3333);
-      final newRatchet = newSession.getRatchetMap()[session.key]!;
+    final result2 = RatchetMapKey.fromJsonKey(test2.toJsonKey());
-      expect(await oldRatchet.equals(newRatchet), true);
+    expect(result2.jid, test2.jid);
-    }
+    expect(result2.deviceId, test2.deviceId);
+  });
+
+  test('Test serializing and deserializing the components of the BTBV manager',
+      () async {
+    // Caroline's BTBV manager
+    final btbv = MemoryBTBVTrustManager();
+    // Example data
+    const aliceJid = 'alice@some.server';
+    const bobJid = 'bob@other.server';
+
+    await btbv.onNewSession(aliceJid, 1);
+    await btbv.setDeviceTrust(aliceJid, 1, BTBVTrustState.verified);
+    await btbv.onNewSession(aliceJid, 2);
+    await btbv.onNewSession(bobJid, 3);
+    await btbv.onNewSession(bobJid, 4);
+
+    final serialized = jsonify(await btbv.toJson());
+    final deviceList =
+        BlindTrustBeforeVerificationTrustManager.deviceListFromJson(
+      serialized,
+    );
+    expect(btbv.devices, deviceList);
+
+    final trustCache =
+        BlindTrustBeforeVerificationTrustManager.trustCacheFromJson(
+      serialized,
+    );
+    expect(btbv.trustCache, trustCache);
+
+    final enableCache =
+        BlindTrustBeforeVerificationTrustManager.enableCacheFromJson(
+      serialized,
+    );
+    expect(btbv.enablementCache, enableCache);
   });
 }

test/trust_test.dart

@@ -12,6 +12,7 @@ void main() {
     // Caroline starts a chat a device from Alice
     await btbv.onNewSession(aliceJid, 1);
     expect(await btbv.isTrusted(aliceJid, 1), true);
+    expect(await btbv.isEnabled(aliceJid, 1), true);
 
     // Caroline meets with Alice and verifies her fingerprint
     await btbv.setDeviceTrust(aliceJid, 1, BTBVTrustState.verified);
@@ -21,6 +22,7 @@ void main() {
     await btbv.onNewSession(aliceJid, 2);
     expect(await btbv.isTrusted(aliceJid, 2), false);
     expect(btbv.getDeviceTrust(aliceJid, 2), BTBVTrustState.notTrusted);
+    expect(await btbv.isEnabled(aliceJid, 2), false);
 
     // Caronline starts a chat with Bob but since they live far apart, Caroline cannot
     // verify his fingerprint.
@@ -32,5 +34,7 @@ void main() {
     expect(await btbv.isTrusted(bobJid, 4), true);
     expect(btbv.getDeviceTrust(bobJid, 3), BTBVTrustState.blindTrust);
     expect(btbv.getDeviceTrust(bobJid, 4), BTBVTrustState.blindTrust);
+    expect(await btbv.isEnabled(bobJid, 3), true);
+    expect(await btbv.isEnabled(bobJid, 4), true);
   });
 }

test/x3dh_test.dart

@@ -71,9 +71,13 @@ void main() {
     var exception = false;
     try {
       await x3dhFromBundle(bundleBob, ikAlice);
-    } catch(e) {
+    } catch (e) {
       exception = true;
-      expect(e is InvalidSignatureException, true, reason: 'Expected InvalidSignatureException, but got $e');
+      expect(
+        e is InvalidSignatureException,
+        true,
+        reason: 'Expected InvalidSignatureException, but got $e',
+      );
     }
 
     expect(exception, true, reason: 'Expected test failure');