fix(moxxy): Fix dependency compatibility with moxxmpp and Moxxy

Rework omemo_dart to finally enable (hopefully) stable E2EE in Moxxy.

.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

.gitlint

@@ -5,6 +5,6 @@ line-length=72
 [title-trailing-punctuation]
 [title-hard-tab]
 [title-match-regex]
-regex=^(feat|fix|test|release|chore|security|docs|refactor|style):.*$
+regex=^(feat|fix|test|release|chore|security|docs|refactor|style|ci):.*$
 [body-trailing-whitespace]
 [body-first-line-empty]

.pubignore

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

.woodpecker.yml

@@ -0,0 +1,22 @@
+pipeline:
+  analysis:
+    image: dart:3.0.7
+    commands:
+      # Proxy requests to pub.dev using pubcached
+      - PUB_HOSTED_URL=http://172.17.0.1:8000 dart pub get
+      - dart analyze --fatal-infos --fatal-warnings
+      - dart test
+    when:
+      path:
+        includes: ['lib/**', 'test/**']
+  notify:
+    image: git.polynom.me/papatutuwawa/woodpecker-xmpp
+    settings:
+      xmpp_is_muc: 1
+      xmpp_tls: 1
+      xmpp_recipient: moxxy-build@muc.moxxy.org
+      xmpp_alias: 2Bot
+    secrets: [ xmpp_jid, xmpp_password, xmpp_server ]
+    when:
+      status:
+        - failure

CHANGELOG.md

@@ -9,9 +9,69 @@
 
 - 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
+
+## 0.5.0
+
+This version is a complete rework of omemo_dart!
+
+- Removed events from `OmemoManager`
+- Removed `OmemoSessionManager`
+- Removed serialization/deserialization code
+- Replace exceptions with errors inside a result type
+- Ratchets and trust data is now loaded and cached on demand
+- Accessing the trust manager must happen via `withTrustManager`
+- Overriding the base implementations is replaced by providing callback functions
+
+## 0.5.1
+
+- Remove `added` and `replaced` from the data passed to the `CommitRatchetsCallback`
+- Added a list of newly added and replaced ratchets to the encryption and decryption results. This is useful for displaying messages like "Contact added a new device"
+
+## 0.6.0
+
+- Bump dependencies to fix running with never version of Dart

README.md

@@ -1,5 +1,7 @@
 # omemo_dart
 
+[![status-badge](https://ci.polynom.me/api/badges/16/status.svg)](https://ci.polynom.me/repos/16)
+
 `omemo_dart` is a Dart library to help developers of Dart/Flutter XMPP clients to implement
 [OMEMO](https://xmpp.org/extensions/xep-0384.html) in its newest version - currently 0.8.3.
 
@@ -28,22 +30,32 @@ 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: ^0.5.0
   # [...]
 
 # [...]
 ```
 
-## Contributing
+### Example
 
-Due to issues with `protobuf`, `omemo_dart` reimplements the Protobuf encoding for the required
-OMEMO messages. As such, `protobuf` is only a dependency for testing that the serialisation and
-deserialisation of the custom implementation. In order to run tests, you need the Protbuf
-compiler. After that, making sure that
-the [Dart Protobuf compiler addon](https://pub.dev/packages/protoc_plugin) and the
-Protobuf compiler itself is in your PATH,
-run `protoc -I=./protobuf/ --dart_out=lib/protobuf/ ./protobuf/schema.proto` in the
-repository's root to generate the real Protobuf bindings.
+This repository includes a documented ["example"](./example/omemo_dart_example.dart) that explains the basic usage of the library while
+leaving out the XMPP specific bits. For a more functional and integrated example, see the `omemo_client.dart` example from
+[moxxmpp](https://codeberg.org/moxxy/moxxmpp).
+
+### Persistence
+
+By default, `omemo_dart` uses in-memory implementations for everything. For a real-world application, this is unsuitable as OMEMO devices would be constantly added.
+In order to allow persistence, your application needs to keep track of the following:
+
+- The `OmemoDevice` assigned to the `OmemoManager`
+- `JID -> [int]`: The device list for each JID
+- `(JID, device) -> Ratchet`: The actual ratchet
+
+If you also use the `BlindTrustBeforeVerificationTrustManager`, you additionally need to keep track of:
+
+- `(JID, device) -> (int, bool)`: The trust level and the enablement state
+
+## Contributing
 
 When submitting a PR, please run the linter using `dart analyze` and make sure that all
 tests still pass using `dart test`.
@@ -56,3 +68,9 @@ 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

@@ -9,4 +9,5 @@ linter:
 
 analyzer:
   exclude:
-    - "lib/protobuf/*.dart"
+    - "lib/src/protobuf/*.dart"
+    - "example/omemo_dart_example.dart"

example/omemo_dart_example.dart

@@ -8,32 +8,54 @@ 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
-  final aliceSession = await OmemoSessionManager.generateNewIdentity(
-    // The bare Jid of Alice as a String
-    aliceJid,
+  // You are Alice and want to begin using OMEMO, so you first create an OmemoManager.
+  final aliceManager = OmemoManager(
+    // Generate Alice's OMEMO device bundle. We can specify how many One-time Prekeys we want, but
+    // 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
-    // 100 OPKs, so let's generate 100. The parameter defaults to 100.
-    //opkAmount: 100,
+    BlindTrustBeforeVerificationTrustManager(),
+    // This function is called whenever we need to send an OMEMO heartbeat to [recipient].
+    // [result] is the encryted data to include. This needs to be wired into your XMPP library's
+    // 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 {},
+    // This function is called whenever our own device bundle has to be republished to our PEP node.
+    // This needs to be wired into your XMPP library's OMEMO implementation.
+    // For simplicity, we use an empty function and imagine it works.
+    (device) 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(
-    bobJid,
-    MemoryBTBVTrustManager(),
-    // Just for illustrative purposes
-    opkAmount: 1,
+  // Bob, on his side, also creates an [OmemoManager] similar to Alice.
+  final bobManager = OmemoManager(
+    await OmemoDevice.generateNewDevice(bobJid),
+    BlindTrustBeforeVerificationTrustManager(),
+    (result, recipient) async => {},
+    (jid) async => [],
+    (jid, id) async => null,
+    (jid) async {},
+    (device) async {},
   );
 
   // Alice prepares to send the message to Bob, so she builds the message stanza and
   // collects all the children of the stanza that should be encrypted into a string.
+  // Note that this leaves out the wrapping stanza, i.e. if we want to send a <message />
+  // we only include the <message />'s children.
   const aliceMessageStanzaBody = '''
   <body>Hello Bob, it's me, Alice!</body>
   <super-secret-element xmlns='super-secret-element' />
@@ -53,31 +75,28 @@ void main() async {
   <time stamp='1969-07-20T21:56:15-05:00' />
 </envelope>
 ''';
- 
-  // 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(
-    // The bare receiver Jid
-    bobJid,
-    // The envelope we want to encrypt
-    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(),
-    ],
+
+  // Next, we encrypt the envelope element using Alice's [OmemoManager]. It will
+  // automatically attempt to fetch the device bundles of Bob.
+  final message = await aliceManager.onOutgoingStanza(
+    const OmemoOutgoingStanza(
+      // The bare receiver Jid
+      [bobJid],
+
+      // The payload we want to encrypt, i.e. the envelope.
+      envelope,
+    ),
   );
 
+  // In a proper implementation, we would 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();
-  // ignore: unused_local_variable
-  final bobDevice = await bobSession.getDevice();
+  final aliceDevice = await aliceManager.getDevice();
   // Since we know we have just one key for Bob, we take a shortcut. However, in the real
   // world, we have to serialise every EncryptedKey to a <key /> element and group them
   // per Jid.
-  final key = message.encryptedKeys[0];
+  final key = message.encryptedKeys[bobJid]![0];
 
   // Note that the key's "kex" attribute refers to key.kex. It just means that the
   // encrypted key also contains the required data for Bob to build a session with Alice.
@@ -87,7 +106,7 @@ void main() async {
   <encrypted xmlns='urn:xmpp:omemo:2'>
     <header sid='${aliceDevice.id}'>
       <keys jid='$bobJid'>
-        <key rid='${key.rid} kex='true'>
+        <key rid='${key.rid} kex='${key.kex}'>
           ${key.value}
         </key>
       </keys>
@@ -105,23 +124,34 @@ void main() async {
   // Bob now receives an OMEMO encrypted message from Alice and wants to decrypt it.
   // Since we have just one key, let's just deserialise the one key by hand.
   final keys = [
-    EncryptedKey(bobJid, key.rid, key.value, true),
+    EncryptedKey(key.rid, key.value, true),
   ];
 
   // Bob extracts the payload and attempts to decrypt it.
   // ignore: unused_local_variable
-  final bobMessage = await bobSession.decryptMessage(
-    // base64 decode the payload
-    base64.decode(payload),
-    // Specify the Jid of the sender
-    aliceJid,
-    // Specify the device identifier of the sender (the "sid" attribute of <header />)
-    aliceDevice.id,
-    // The deserialised keys
-    keys,
+  final bobMessage = await bobManager.onIncomingStanza(
+    OmemoIncomingStanza(
+      // The bare sender JID of the message. In this case, it's Alice's.
+      aliceJid,
+      // The 'sid' attribute of the <header /> element. Here, we know that Alice only has one device.
+      aliceDevice.id,
+
+      /// 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,
+
+      /// Since we did not receive this message due to a catch-up mechanism, like MAM, we
+      /// set this to false. If we, however, did use a catch-up mechanism, we must set this
+      /// to true to prevent the OPKs from being replaced.
+      false,
+    ),
   );
 
-  // All Bob has to do now is replace the OMEMO wrapper element 
+  // All Bob has to do now is replace the OMEMO wrapper element
   // <encrypted xmlns='urn:xmpp:omemo:2' />) with the content of the <content /> element
   // of the envelope we just decrypted.
 

flake.lock

@@ -1,12 +1,15 @@
 {
   "nodes": {
     "flake-utils": {
+      "inputs": {
+        "systems": "systems"
+      },
       "locked": {
-        "lastModified": 1656065134,
-        "narHash": "sha256-oc6E6ByIw3oJaIyc67maaFcnjYOz1mMcOtHxbEf9NwQ=",
+        "lastModified": 1692799911,
+        "narHash": "sha256-3eihraek4qL744EvQXsK1Ha6C3CR7nnT8X2qWap4RNk=",
         "owner": "numtide",
         "repo": "flake-utils",
-        "rev": "bee6a7250dd1b01844a2de7e02e4df7d8a0a206c",
+        "rev": "f9e7cf818399d17d347f847525c5a5a8032e4e44",
         "type": "github"
       },
       "original": {
@@ -17,16 +20,16 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1657540956,
-        "narHash": "sha256-ihGbOFWtAkENwxBE5kV/yWt2MncvW+BObLDsmxCLo/Q=",
-        "owner": "NANASHI0X74",
+        "lastModified": 1727586919,
+        "narHash": "sha256-e/YXG0tO5GWHDS8QQauj8aj4HhXEm602q9swrrlTlKQ=",
+        "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "043de04db8a6b0391b3fefaaade160514d866946",
+        "rev": "2dcd9c55e8914017226f5948ac22c53872a13ee2",
         "type": "github"
       },
       "original": {
-        "owner": "NANASHI0X74",
-        "ref": "flutter-3-0-0",
+        "owner": "NixOS",
+        "ref": "nixpkgs-unstable",
         "repo": "nixpkgs",
         "type": "github"
       }
@@ -36,6 +39,21 @@
         "flake-utils": "flake-utils",
         "nixpkgs": "nixpkgs"
       }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
     }
   },
   "root": "root",

flake.nix

@@ -1,7 +1,7 @@
 {
   description = "omemo_dart";
   inputs = {
-    nixpkgs.url = "github:NANASHI0X74/nixpkgs/flutter-3-0-0";
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
     flake-utils.url = "github:numtide/flake-utils";
   };
   outputs = { self, nixpkgs, flake-utils }: flake-utils.lib.eachDefaultSystem (system: let

lib/omemo_dart.dart

@@ -8,10 +8,12 @@ export 'src/omemo/bundle.dart';
 export 'src/omemo/device.dart';
 export 'src/omemo/encrypted_key.dart';
 export 'src/omemo/encryption_result.dart';
-export 'src/omemo/events.dart';
+export 'src/omemo/errors.dart';
 export 'src/omemo/fingerprint.dart';
+export 'src/omemo/omemo.dart';
+export 'src/omemo/ratchet_data.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/src/common/constants.dart

@@ -0,0 +1,11 @@
+/// The overarching assumption is that we use Ed25519 keys for the identity keys
+const omemoX3DHInfoString = 'OMEMO X3DH';
+
+/// The info used for when encrypting the AES key for the actual payload.
+const omemoPayloadInfoString = 'OMEMO Payload';
+
+/// Info string for ENCRYPT
+const encryptHkdfInfoString = 'OMEMO Message Key Material';
+
+/// Amount of messages we may skip per session
+const maxSkip = 1000;

lib/src/crypto.dart

@@ -1,12 +1,18 @@
 import 'dart:convert';
 import 'package:cryptography/cryptography.dart';
+import 'package:moxlib/moxlib.dart';
+import 'package:omemo_dart/src/errors.dart';
 import 'package:omemo_dart/src/keys.dart';
 
 /// Performs X25519 with [kp] and [pk]. If [identityKey] is set, then
 /// 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;
 
@@ -17,15 +23,14 @@ Future<List<int>> omemoDH(OmemoKeyPair kp, OmemoPublicKey pk, int identityKey) a
   }
 
   final shared = await Cryptography.instance.x25519().sharedSecretKey(
-    keyPair: await ckp.asKeyPair(),
-    remotePublicKey: cpk.asPublicKey(),
-  );
+        keyPair: await ckp.asKeyPair(),
+        remotePublicKey: cpk.asPublicKey(),
+      );
 
   return shared.extractBytes();
 }
 
 class HkdfKeyResult {
-
   const HkdfKeyResult(this.encryptionKey, this.authenticationKey, this.iv);
   final List<int> encryptionKey;
   final List<int> authenticationKey;
@@ -35,7 +40,8 @@ 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({
@@ -59,13 +65,21 @@ Future<HkdfKeyResult> deriveEncryptionKeys(List<int> input, String info) async {
     info: utf8.encode(info),
   );
   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,
   );
@@ -80,17 +94,27 @@ 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<Result<MalformedCiphertextError, List<int>>> aes256CbcDecrypt(
+  List<int> ciphertext,
+  List<int> key,
+  List<int> iv,
+) async {
   final algorithm = AesCbc.with256bits(
     macAlgorithm: MacAlgorithm.empty,
   );
-  return algorithm.decrypt(
-    NoMacSecretBox(
-      ciphertext,
-      nonce: iv,
-    ),
-    secretKey: SecretKey(key),
-  );
+  try {
+    return Result(
+      await algorithm.decrypt(
+        NoMacSecretBox(
+          ciphertext,
+          nonce: iv,
+        ),
+        secretKey: SecretKey(key),
+      ),
+    );
+  } catch (ex) {
+    return Result(MalformedCiphertextError(ex));
+  }
 }
 
 /// OMEMO often uses the output of a HMAC-SHA-256 truncated to its first 16 bytes.

lib/src/double_ratchet/crypto.dart

@@ -1,48 +0,0 @@
-import 'package:omemo_dart/src/crypto.dart';
-import 'package:omemo_dart/src/errors.dart';
-import 'package:omemo_dart/src/helpers.dart';
-import 'package:omemo_dart/src/protobuf/omemo_authenticated_message.dart';
-import 'package:omemo_dart/src/protobuf/omemo_message.dart';
-
-/// Info string for ENCRYPT
-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 {
-  // Generate encryption, authentication key and IV
-  final keys = await deriveEncryptionKeys(mk, encryptHkdfInfoString);
-  final ciphertext = await aes256CbcEncrypt(plaintext, keys.encryptionKey, keys.iv);
-  
-  final header = OmemoMessage.fromBuffer(associatedData.sublist(sessionAd.length))
-    ..ciphertext = ciphertext;
-  final headerBytes = header.writeToBuffer();
-  final hmacInput = concat([sessionAd, headerBytes]);
-  final hmacResult = await truncatedHmac(hmacInput, keys.authenticationKey);
-  final message = OmemoAuthenticatedMessage()
-    ..mac = hmacResult
-    ..message = headerBytes;
-  return message.writeToBuffer();
-}
-
-/// 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 {
-  // Generate encryption, authentication key and IV
-  final keys = await deriveEncryptionKeys(mk, encryptHkdfInfoString);
-  
-  // Assumption ciphertext is a OMEMOAuthenticatedMessage
-  final message = OmemoAuthenticatedMessage.fromBuffer(ciphertext);
-  final header = OmemoMessage.fromBuffer(message.message!);
-
-  final hmacInput = concat([sessionAd, header.writeToBuffer()]);
-  final hmacResult = await truncatedHmac(hmacInput, keys.authenticationKey);
-
-  if (!listsEqual(hmacResult, message.mac!)) {
-    throw InvalidMessageHMACException();
-  }
-
-  return aes256CbcDecrypt(header.ciphertext!, keys.encryptionKey, keys.iv);
-}

lib/src/double_ratchet/double_ratchet.dart

@@ -1,49 +1,25 @@
-import 'dart:convert';
 import 'package:cryptography/cryptography.dart';
+import 'package:hex/hex.dart';
 import 'package:meta/meta.dart';
+import 'package:moxlib/moxlib.dart';
+import 'package:omemo_dart/src/common/constants.dart';
 import 'package:omemo_dart/src/crypto.dart';
-import 'package:omemo_dart/src/double_ratchet/crypto.dart';
 import 'package:omemo_dart/src/double_ratchet/kdf.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/protobuf/omemo_message.dart';
-
-/// Amount of messages we may skip per session
-const maxSkip = 1000;
-
-class RatchetStep {
-
-  const RatchetStep(this.header, this.ciphertext);
-  final OmemoMessage header;
-  final List<int> ciphertext;
-}
+import 'package:omemo_dart/src/protobuf/schema.pb.dart';
 
 @immutable
 class SkippedKey {
-
   const SkippedKey(this.dh, this.n);
 
-  factory SkippedKey.fromJson(Map<String, dynamic> data) {
-    return SkippedKey(
-      OmemoPublicKey.fromBytes(
-        base64.decode(data['public']! as String),
-        KeyPairType.x25519,
-      ),
-      data['n']! as int,
-    );
-  }
-
+  /// The DH public key for which we skipped a message key.
   final OmemoPublicKey dh;
+
+  /// The associated number of the message key we skipped.
   final int n;
 
-  Future<Map<String, dynamic>> toJson() async {
-    return {
-      'public': base64.encode(await dh.getBytes()),
-      'n': n,
-    };
-  }
-  
   @override
   bool operator ==(Object other) {
     return other is SkippedKey && other.dh == dh && other.n == n;
@@ -53,76 +29,45 @@ class SkippedKey {
   int get hashCode => dh.hashCode ^ n.hashCode;
 }
 
-class OmemoDoubleRatchet {
+@immutable
+class KeyExchangeData {
+  const KeyExchangeData(
+    this.pkId,
+    this.spkId,
+    this.ik,
+    this.ek,
+  );
 
+  /// The id of the used OPK.
+  final int pkId;
+
+  /// The id of the used SPK.
+  final int spkId;
+
+  /// The ephemeral key used while the key exchange.
+  final OmemoPublicKey ek;
+
+  /// The identity key used in the key exchange.
+  final OmemoPublicKey ik;
+}
+
+class OmemoDoubleRatchet {
   OmemoDoubleRatchet(
     this.dhs, // DHs
     this.dhr, // DHr
-    this.rk,  // RK
+    this.rk, // RK
     this.cks, // CKs
     this.ckr, // CKr
-    this.ns,  // Ns
-    this.nr,  // Nr
-    this.pn,  // Pn
+    this.ns, // Ns
+    this.nr, // Nr
+    this.pn, // Pn
     this.ik,
     this.sessionAd,
     this.mkSkipped, // MKSKIPPED
     this.acknowledged,
+    this.kex,
   );
 
-  factory OmemoDoubleRatchet.fromJson(Map<String, dynamic> data) {
-    /*
-    {
-      'dhs': 'base/64/encoded',
-      'dhs_pub': 'base/64/encoded',
-      'dhr': null | 'base/64/encoded',
-      'rk': 'base/64/encoded',
-      'cks': null | 'base/64/encoded',
-      'ckr': null | 'base/64/encoded',
-      'ns': 0,
-      'nr': 0,
-      'pn': 0,
-      'ik_pub': 'base/64/encoded',
-      'session_ad': 'base/64/encoded',
-      'acknowledged': true | false,
-      'mkskipped': [
-        {
-          'key': 'base/64/encoded',
-          'public': 'base/64/encoded',
-          'n': 0
-        }, ...
-      ]
-    }
-    */
-    final mkSkipped = <SkippedKey, List<int>>{};
-    for (final entry in data['mkskipped']! as List<Map<String, dynamic>>) {
-      final key = SkippedKey.fromJson(entry);
-      mkSkipped[key] = base64.decode(entry['key']! as String);
-    }
-    
-    return OmemoDoubleRatchet(
-      OmemoKeyPair.fromBytes(
-        base64.decode(data['dhs_pub']! as String),
-        base64.decode(data['dhs']! as String),
-        KeyPairType.x25519,
-      ),
-      decodeKeyIfNotNull(data, 'dhr', KeyPairType.x25519),
-      base64.decode(data['rk']! as String),
-      base64DecodeIfNotNull(data, 'cks'),
-      base64DecodeIfNotNull(data, 'ckr'),
-      data['ns']! as int,
-      data['nr']! as int,
-      data['pn']! as int,
-      OmemoPublicKey.fromBytes(
-        base64.decode(data['ik_pub']! as String),
-        KeyPairType.ed25519,
-      ),
-      base64.decode(data['session_ad']! as String),
-      mkSkipped,
-      data['acknowledged']! as bool,
-    );
-  }
-  
   /// Sending DH keypair
   OmemoKeyPair dhs;
 
@@ -146,11 +91,16 @@ class OmemoDoubleRatchet {
   /// The IK public key from the chat partner. Not used for the actual encryption but
   /// for verification purposes
   final OmemoPublicKey ik;
-  
+
+  /// Associated data for this ratchet.
   final List<int> sessionAd;
 
+  /// List of skipped message keys.
   final Map<SkippedKey, List<int>> mkSkipped;
 
+  /// The key exchange that was used for initiating the session.
+  final KeyExchangeData kex;
+
   /// Indicates whether we received an empty OMEMO message after building a session with
   /// the device.
   bool acknowledged;
@@ -158,17 +108,24 @@ 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,
+    int spkId,
+    OmemoPublicKey ik,
+    OmemoPublicKey ownIk,
+    OmemoPublicKey ek,
+    List<int> sk,
+    List<int> ad,
+    int pkId,
+  ) async {
     final dhs = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
-    final dhr = spk;
-    final rk  = await kdfRk(sk, await omemoDH(dhs, dhr, 0));
-    final cks = rk;
+    final rk = await kdfRk(sk, await omemoDH(dhs, spk, 0));
 
     return OmemoDoubleRatchet(
       dhs,
-      dhr,
-      rk,
-      cks,
+      spk,
+      List.from(rk),
+      List.from(rk),
       null,
       0,
       0,
@@ -177,6 +134,12 @@ class OmemoDoubleRatchet {
       ad,
       {},
       false,
+      KeyExchangeData(
+        pkId,
+        spkId,
+        ownIk,
+        ek,
+      ),
     );
   }
 
@@ -184,7 +147,15 @@ 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,
+    int spkId,
+    OmemoPublicKey ik,
+    int pkId,
+    OmemoPublicKey ek,
+    List<int> sk,
+    List<int> ad,
+  ) async {
     return OmemoDoubleRatchet(
       spk,
       null,
@@ -198,53 +169,52 @@ class OmemoDoubleRatchet {
       ad,
       {},
       true,
+      KeyExchangeData(
+        pkId,
+        spkId,
+        ik,
+        ek,
+      ),
     );
   }
 
-  Future<Map<String, dynamic>> toJson() async {
-    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);
-
-      mkSkippedSerialised.add(result);
-    }
-    
-    return {
-      'dhs': base64.encode(await dhs.sk.getBytes()),
-      'dhs_pub': base64.encode(await dhs.pk.getBytes()),
-      'dhr': dhr != null ? base64.encode(await dhr!.getBytes()) : null,
-      'rk': base64.encode(rk),
-      'cks': cks != null ? base64.encode(cks!) : null,
-      'ckr': ckr != null ? base64.encode(ckr!) : null,
-      'ns': ns,
-      'nr': nr,
-      'pn': pn,
-      'ik_pub': base64.encode(await ik.getBytes()),
-      'session_ad': base64.encode(sessionAd),
-      'mkskipped': mkSkippedSerialised,
-      'acknowledged': acknowledged,
-    };
-  }
-  
-  Future<List<int>?> _trySkippedMessageKeys(OmemoMessage header, List<int> ciphertext) async {
-    final key = SkippedKey(
-      OmemoPublicKey.fromBytes(header.dhPub!, KeyPairType.x25519),
-      header.n!,
+  /// Performs a single ratchet step in case we received a new
+  /// public key in [header].
+  Future<void> _dhRatchet(OMEMOMessage header) async {
+    pn = ns;
+    ns = 0;
+    nr = 0;
+    dhr = OmemoPublicKey.fromBytes(header.dhPub, KeyPairType.x25519);
+    final newRk1 = await kdfRk(
+      rk,
+      await omemoDH(
+        dhs,
+        dhr!,
+        0,
+      ),
     );
-    if (mkSkipped.containsKey(key)) {
-      final mk = mkSkipped[key]!;
-      mkSkipped.remove(key);
+    rk = List.from(newRk1);
+    ckr = List.from(newRk1);
 
-      return decrypt(mk, ciphertext, concat([sessionAd, header.writeToBuffer()]), sessionAd);
-    }
-
-    return null;
+    dhs = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
+    final newRk2 = await kdfRk(
+      rk,
+      await omemoDH(
+        dhs,
+        dhr!,
+        0,
+      ),
+    );
+    rk = List.from(newRk2);
+    cks = List.from(newRk2);
   }
 
-  Future<void> _skipMessageKeys(int until) async {
+  /// Skip (and keep track of) message keys until our receive counter is
+  /// equal to [until]. If we would skip too many messages, returns
+  /// a [SkippingTooManyKeysError]. If not, returns null.
+  Future<OmemoError?> _skipMessageKeys(int until) async {
     if (nr + maxSkip < until) {
-      throw SkippingTooManyMessagesException();
+      return SkippingTooManyKeysError();
     }
 
     if (ckr != null) {
@@ -252,96 +222,195 @@ class OmemoDoubleRatchet {
         final newCkr = await kdfCk(ckr!, kdfCkNextChainKey);
         final mk = await kdfCk(ckr!, kdfCkNextMessageKey);
         ckr = newCkr;
+
         mkSkipped[SkippedKey(dhr!, nr)] = mk;
         nr++;
       }
     }
+
+    return null;
   }
 
-  Future<void> _dhRatchet(OmemoMessage header) async {
-    pn = header.n!;
-    ns = 0;
-    nr = 0;
-    dhr = OmemoPublicKey.fromBytes(header.dhPub!, KeyPairType.x25519);
-
-    final newRk = await kdfRk(rk, await omemoDH(dhs, dhr!, 0));
-    rk = newRk;
-    ckr = newRk;
-    dhs = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
-    final newNewRk = await kdfRk(rk, await omemoDH(dhs, dhr!, 0));
-    rk = newNewRk;
-    cks = newNewRk;
-  }
-
-  /// Encrypt [plaintext] using the Double Ratchet.
-  Future<RatchetStep> ratchetEncrypt(List<int> plaintext) async {
-    final newCks = await kdfCk(cks!, kdfCkNextChainKey);
-    final mk = await kdfCk(cks!, kdfCkNextMessageKey);
-
-    cks = newCks;
-    final header = OmemoMessage()
-      ..dhPub = await dhs.pk.getBytes()
-      ..pn = pn
-      ..n = ns;
-
-    ns++;
-
-    return RatchetStep(
-      header,
-      await encrypt(mk, plaintext, concat([sessionAd, header.writeToBuffer()]), sessionAd),
-    );
-  }
-
-  /// Decrypt a [ciphertext] that was sent with the header [header] using the Double
-  /// Ratchet. Returns the decrypted (raw) plaintext.
+  /// Decrypt [ciphertext] using keys derived from the message key [mk]. Also computes the
+  /// HMAC from the [OMEMOMessage] embedded in [message].
   ///
-  /// Throws an SkippingTooManyMessagesException if too many messages were to be skipped.
-  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) {
-      return plaintext;
+  /// If the computed HMAC does not match the HMAC in [message], returns
+  /// [InvalidMessageHMACError]. If it matches, returns the decrypted
+  /// payload.
+  Future<Result<OmemoError, List<int>>> _decrypt(
+    OMEMOAuthenticatedMessage message,
+    List<int> ciphertext,
+    List<int> mk,
+  ) async {
+    final keys = await deriveEncryptionKeys(mk, encryptHkdfInfoString);
+
+    final hmacInput = concat([sessionAd, message.message]);
+    final hmacResult = await truncatedHmac(hmacInput, keys.authenticationKey);
+    if (!listsEqual(hmacResult, message.mac)) {
+      return Result(InvalidMessageHMACError());
     }
 
-    final dhPubMatches = listsEqual(
-      header.dhPub ?? <int>[],
-      await dhr?.getBytes() ?? <int>[],
+    final plaintext =
+        await aes256CbcDecrypt(ciphertext, keys.encryptionKey, keys.iv);
+    if (plaintext.isType<MalformedCiphertextError>()) {
+      return Result(plaintext.get<MalformedCiphertextError>());
+    }
+
+    return Result(plaintext.get<List<int>>());
+  }
+
+  /// Checks whether we could decrypt the payload in [header] with a skipped key. If yes,
+  /// attempts to decrypt it. If not, returns null.
+  ///
+  /// If the decryption is successful, returns the plaintext payload. If an error occurs, like
+  /// an [InvalidMessageHMACError], that is returned instead.
+  Future<Result<OmemoError, List<int>?>> _trySkippedMessageKeys(
+    OMEMOAuthenticatedMessage message,
+    OMEMOMessage header,
+  ) async {
+    final key = SkippedKey(
+      OmemoPublicKey.fromBytes(header.dhPub, KeyPairType.x25519),
+      header.n,
     );
-    if (!dhPubMatches) {
-      await _skipMessageKeys(header.pn!);
+    if (mkSkipped.containsKey(key)) {
+      final mk = mkSkipped[key]!;
+      mkSkipped.remove(key);
+
+      return _decrypt(message, header.ciphertext, mk);
+    }
+
+    return const Result(null);
+  }
+
+  /// Decrypt the payload (deeply) embedded in [message].
+  ///
+  /// If everything goes well, returns the plaintext payload. If an error occurs, that
+  /// is returned instead.
+  Future<Result<OmemoError, List<int>>> ratchetDecrypt(
+    OMEMOAuthenticatedMessage message,
+  ) async {
+    final header = OMEMOMessage.fromBuffer(message.message);
+
+    // Try skipped keys
+    final plaintextRaw = await _trySkippedMessageKeys(message, header);
+    if (plaintextRaw.isType<OmemoError>()) {
+      // Propagate the error
+      return Result(plaintextRaw.get<OmemoError>());
+    }
+
+    final plaintext = plaintextRaw.get<List<int>?>();
+    if (plaintext != null) {
+      return Result(plaintext);
+    }
+
+    if (dhr == null || !listsEqual(header.dhPub, await dhr!.getBytes())) {
+      final skipResult1 = await _skipMessageKeys(header.pn);
+      if (skipResult1 != null) {
+        return Result(skipResult1);
+      }
+
       await _dhRatchet(header);
     }
-    
-    await _skipMessageKeys(header.n!);
-    final newCkr = await kdfCk(ckr!, kdfCkNextChainKey);
+
+    final skipResult2 = await _skipMessageKeys(header.n);
+    if (skipResult2 != null) {
+      return Result(skipResult2);
+    }
+
+    final ck = await kdfCk(ckr!, kdfCkNextChainKey);
     final mk = await kdfCk(ckr!, kdfCkNextMessageKey);
-    ckr = newCkr;
+    ckr = ck;
     nr++;
 
-    return decrypt(mk, ciphertext, concat([sessionAd, header.writeToBuffer()]), sessionAd);
+    return _decrypt(message, header.ciphertext, mk);
+  }
+
+  /// Encrypt the payload [plaintext] using the double ratchet session.
+  Future<OMEMOAuthenticatedMessage> ratchetEncrypt(List<int> plaintext) async {
+    // Advance the ratchet
+    final ck = await kdfCk(cks!, kdfCkNextChainKey);
+    final mk = await kdfCk(cks!, kdfCkNextMessageKey);
+    cks = ck;
+
+    // Generate encryption, authentication key and IV
+    final keys = await deriveEncryptionKeys(mk, encryptHkdfInfoString);
+    final ciphertext =
+        await aes256CbcEncrypt(plaintext, keys.encryptionKey, keys.iv);
+
+    // Fill-in the header and serialize it here so we do it only once
+    final header = OMEMOMessage()
+      ..dhPub = await dhs.pk.getBytes()
+      ..pn = pn
+      ..n = ns
+      ..ciphertext = ciphertext;
+    final headerBytes = header.writeToBuffer();
+
+    // Increment the send counter
+    ns++;
+
+    final newAd = concat([sessionAd, headerBytes]);
+    final hmac = await truncatedHmac(newAd, keys.authenticationKey);
+    return OMEMOAuthenticatedMessage()
+      ..mac = hmac
+      ..message = headerBytes;
+  }
+
+  /// Returns a copy of the ratchet.
+  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,
+      kex,
+    );
+  }
+
+  /// Computes the fingerprint of the double ratchet, according to
+  /// XEP-0384.
+  Future<String> get fingerprint async {
+    final curveKey = await ik.toCurve25519();
+    return HEX.encode(
+      await curveKey.getBytes(),
+    );
   }
 
   @visibleForTesting
   Future<bool> equals(OmemoDoubleRatchet other) async {
-    // ignore: invalid_use_of_visible_for_testing_member
-    final dhrMatch = dhr == null ? other.dhr == null : await dhr!.equals(other.dhr!);
-    final ckrMatch = ckr == null ? other.ckr == null : listsEqual(ckr!, other.ckr!);
-    final cksMatch = cks == null ? other.cks == null : listsEqual(cks!, other.cks!);
- 
+    final dhrMatch = dhr == null
+        ? other.dhr == null
+        :
+        // ignore: invalid_use_of_visible_for_testing_member
+        other.dhr != null && await dhr!.equals(other.dhr!);
+    final ckrMatch = ckr == null
+        ? 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);
     // ignore: invalid_use_of_visible_for_testing_member
     final ikMatch = await ik.equals(other.ik);
-    
+
     return dhsMatch &&
-      ikMatch &&
-      dhrMatch &&
-      listsEqual(rk, other.rk) &&
-      cksMatch &&
-      ckrMatch &&
-      ns == other.ns &&
-      nr == other.nr &&
-      pn == other.pn &&
-      listsEqual(sessionAd, other.sessionAd);
+        ikMatch &&
+        dhrMatch &&
+        listsEqual(rk, other.rk) &&
+        cksMatch &&
+        ckrMatch &&
+        ns == other.ns &&
+        nr == other.nr &&
+        pn == other.pn &&
+        listsEqual(sessionAd, other.sessionAd);
   }
 }

lib/src/double_ratchet/kdf.dart

@@ -8,7 +8,7 @@ const kdfRkInfoString = 'OMEMO Root Chain';
 const kdfCkNextMessageKey = 0x01;
 const kdfCkNextChainKey = 0x02;
 
-/// Signals KDF_CK function as specified by OMEMO 0.8.0.
+/// Signals KDF_CK function as specified by OMEMO 0.8.3.
 Future<List<int>> kdfCk(List<int> ck, int constant) async {
   final hkdf = Hkdf(hmac: Hmac(Sha256()), outputLength: 32);
   final result = await hkdf.deriveKey(
@@ -19,7 +19,7 @@ Future<List<int>> kdfCk(List<int> ck, int constant) async {
   return result.extractBytes();
 }
 
-/// Signals KDF_RK function as specified by OMEMO 0.8.0.
+/// Signals KDF_RK function as specified by OMEMO 0.8.3.
 Future<List<int>> kdfRk(List<int> rk, List<int> dhOut) async {
   final algorithm = Hkdf(
     hmac: Hmac(Sha256()),

lib/src/errors.dart

@@ -1,32 +1,39 @@
+abstract class OmemoError {}
+
 /// Triggered during X3DH if the signature if the SPK does verify to the actual SPK.
-class InvalidSignatureException implements Exception {
-  String errMsg() => 'The signature of the SPK does not match the provided signature';
-}
+class InvalidKeyExchangeSignatureError extends OmemoError {}
 
 /// 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 {
-  String errMsg() => 'The computed HMAC does not match the provided HMAC';
-}
+class InvalidMessageHMACError extends OmemoError {}
 
 /// Triggered by the Double Ratchet if skipping messages would cause skipping more than
 /// MAXSKIP messages
-class SkippingTooManyMessagesException implements Exception {
-  String errMsg() => 'Skipping messages would cause a skip bigger than MAXSKIP';
-}
+class SkippingTooManyKeysError extends OmemoError {}
 
 /// Triggered by the Session Manager if the message key is not encrypted for the device.
-class NotEncryptedForDeviceException 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 {
-  String errMsg() => 'No key available for decrypting the message';
-}
+class NotEncryptedForDeviceError extends OmemoError {}
 
 /// 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 {
-  String errMsg() => 'Unknown Signed Prekey used.';
+class UnknownSignedPrekeyError extends OmemoError {}
+
+/// 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 NoKeyMaterialAvailableError extends OmemoError {}
+
+/// A non-key-exchange message was received that was encrypted for our device, but we have no ratchet with
+/// the device that sent the message.
+class NoSessionWithDeviceError extends OmemoError {}
+
+/// Caused when the AES-256 CBC decryption failed.
+class MalformedCiphertextError extends OmemoError {
+  MalformedCiphertextError(this.ex);
+
+  /// The exception that was raised while decryption.
+  final Object ex;
 }
+
+/// Caused by an empty <key /> element
+class MalformedEncryptedKeyError extends OmemoError {}

lib/src/helpers.dart

@@ -1,7 +1,5 @@
 import 'dart:convert';
 import 'dart:math';
-import 'package:cryptography/cryptography.dart';
-import 'package:omemo_dart/src/keys.dart';
 
 /// Flattens [inputs] and concatenates the elements.
 List<int> concat(List<List<int>> inputs) {
@@ -43,33 +41,35 @@ int generateRandom32BitNumber() {
   return Random.secure().nextInt(4294967295 /*pow(2, 32) - 1*/);
 }
 
-OmemoPublicKey? decodeKeyIfNotNull(Map<String, dynamic> map, String key, KeyPairType type) {
-  if (map[key] == null) return null;
+/// Describes the differences between two lists in terms of its items.
+class ListDiff<T> {
+  ListDiff(this.added, this.removed);
 
-  return OmemoPublicKey.fromBytes(
-    base64.decode(map[key]! as String),
-    type,
-  );
+  /// The items that were added.
+  final List<T> added;
+
+  /// The items that were removed.
+  final List<T> removed;
 }
 
-List<int>? base64DecodeIfNotNull(Map<String, dynamic> map, String key) {
-  if (map[key] == null) return null;
-
-  return base64.decode(map[key]! as String);
+extension AppendToListOrCreateExtension<K, V> on Map<K, List<V>> {
+  /// Create or append [value] to the list identified with key [key].
+  void appendOrCreate(K key, V value, {bool checkExistence = false}) {
+    if (containsKey(key)) {
+      if (!checkExistence) {
+        this[key]!.add(value);
+      }
+      if (!this[key]!.contains(value)) {
+        this[key]!.add(value);
+      }
+    } else {
+      this[key] = [value];
+    }
+  }
 }
 
-String? base64EncodeIfNotNull(List<int>? bytes) {
-  if (bytes == null) return null;
-
-  return base64.encode(bytes);
-}
-
-OmemoKeyPair? decodeKeyPairIfNotNull(String? pk, String? sk, KeyPairType type) {
-  if (pk == null || sk == null) return null;
-
-  return OmemoKeyPair.fromBytes(
-    base64.decode(pk),
-    base64.decode(sk),
-    type,
-  );
+extension StringFromBase64Extension on String {
+  /// Base64-decode this string. Useful for doing `someString?.fromBase64()` instead
+  /// of `someString != null ? base64Decode(someString) : null`.
+  List<int> fromBase64() => base64Decode(this);
 }

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) {
@@ -22,7 +21,7 @@ class OmemoPublicKey {
   }
 
   final SimplePublicKey _pubkey;
-  
+
   KeyPairType get type => _pubkey.type;
 
   /// Return the bytes that comprise the public key.
@@ -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(
@@ -40,30 +42,35 @@ 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(
-      await getBytes(),
-      await key.getBytes(),
-    );
+    return type == key.type &&
+        listsEqual(
+          await getBytes(),
+          await key.getBytes(),
+        );
   }
 }
 
 class OmemoPrivateKey {
-
   const OmemoPrivateKey(this._privkey, this.type);
   final List<int> _privkey;
   final KeyPairType type;
 
   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(
@@ -76,21 +83,25 @@ class OmemoPrivateKey {
 
   @visibleForTesting
   Future<bool> equals(OmemoPrivateKey key) async {
-    return type == key.type && listsEqual(
-      await getBytes(),
-      await key.getBytes(),
-    );
+    return type == key.type &&
+        listsEqual(
+          await getBytes(),
+          await key.getBytes(),
+        );
   }
 }
 
 /// 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) {
@@ -122,7 +136,7 @@ class OmemoKeyPair {
     }
 
     final kpd = await kp.extract();
-    
+
     return OmemoKeyPair(
       OmemoPublicKey(await kp.extractPublicKey()),
       OmemoPrivateKey(await kpd.extractPrivateKeyBytes(), type),
@@ -133,10 +147,13 @@ class OmemoKeyPair {
   final KeyPairType type;
   final OmemoPublicKey pk;
   final OmemoPrivateKey sk;
-  
+
   /// 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(),
@@ -156,7 +173,7 @@ class OmemoKeyPair {
   @visibleForTesting
   Future<bool> equals(OmemoKeyPair pair) async {
     return type == pair.type &&
-      await pk.equals(pair.pk) &&
-      await sk.equals(pair.sk);
+        await pk.equals(pair.pk) &&
+        await sk.equals(pair.sk);
   }
 }

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/decryption_result.dart

@@ -0,0 +1,30 @@
+import 'package:meta/meta.dart';
+import 'package:omemo_dart/src/errors.dart';
+
+@immutable
+class DecryptionResult {
+  const DecryptionResult(
+    this.payload,
+    this.usedOpkId,
+    this.newRatchets,
+    this.replacedRatchets,
+    this.error,
+  );
+
+  /// The decrypted payload or null, if it was an empty OMEMO message.
+  final String? payload;
+
+  /// In case a key exchange has been performed: The id of the used OPK. Useful for
+  /// replacing the OPK after a message catch-up.
+  final int? usedOpkId;
+
+  /// Mapping of JIDs to a list of device ids for which we created a new ratchet session.
+  final Map<String, List<int>> newRatchets;
+
+  /// Similar to [newRatchets], but the ratchets listed in [replacedRatchets] where also existent before
+  /// and replaced with the new ratchet.
+  final Map<String, List<int>> replacedRatchets;
+
+  /// The error that occurred during decryption or null, if no error occurred.
+  final OmemoError? 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 {
-
-  const Device(
+class OmemoDevice {
+  const OmemoDevice(
     this.jid,
     this.id,
     this.ik,
@@ -22,69 +22,11 @@ class Device {
     this.opks,
   );
 
-  /// Deserialize the Device
-  factory Device.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.
-    /*
-    {
-      'jid': 'alice@...',
-      'id': 123,
-      'ik': 'base/64/encoded',
-      'ik_pub': 'base/64/encoded',
-      'spk': 'base/64/encoded',
-      'spk_pub': 'base/64/encoded',
-      'spk_id': 123,
-      'spk_sig': 'base/64/encoded',
-      'old_spk': 'base/64/encoded',
-      'old_spk_pub': 'base/64/encoded',
-      'old_spk_id': 122,
-      'opks': [
-        {
-          'id': 0,
-          'public': 'base/64/encoded',
-          'private': 'base/64/encoded'
-        }, ...
-      ]
-    }
-    */
-    final opks = <int, OmemoKeyPair>{};
-    for (final opk in data['opks']! as List<Map<String, dynamic>>) {
-      opks[opk['id']! as int] = OmemoKeyPair.fromBytes(
-        base64.decode(opk['public']! as String),
-        base64.decode(opk['private']! as String),
-        KeyPairType.x25519,
-      );
-    }
-
-    return Device(
-      data['jid']! as String,
-      data['id']! as int,
-      OmemoKeyPair.fromBytes(
-        base64.decode(data['ik_pub']! as String),
-        base64.decode(data['ik']! as String),
-        KeyPairType.ed25519,
-      ),
-      OmemoKeyPair.fromBytes(
-        base64.decode(data['spk_pub']! as String),
-        base64.decode(data['spk']! as String),
-        KeyPairType.x25519,
-      ),
-      data['spk_id']! as int,
-      base64.decode(data['spk_sig']! as String),
-      decodeKeyPairIfNotNull(
-        data['old_spk_pub'] as String?,
-        data['old_spk'] as String?,
-        KeyPairType.x25519,
-      ),
-      data['old_spk_id'] as int?,
-      opks,
-    );
-  }
-  
   /// 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);
@@ -93,15 +35,24 @@ class Device {
 
     final opks = <int, OmemoKeyPair>{};
     for (var i = 0; i < opkAmount; i++) {
-      opks[i] = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
+      // Generate unique ids for each key
+      while (true) {
+        final opkId = generateRandom32BitNumber();
+        if (opks.containsKey(opkId)) {
+          continue;
+        }
+
+        opks[opkId] = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
+        break;
+      }
     }
 
-    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
   final String jid;
-  
+
   /// The device Id
   final int id;
 
@@ -110,13 +61,16 @@ 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 +80,23 @@ 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 {
-    opks[id] = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
-    
-    return Device(
+  Future<OmemoDevice> replaceOnetimePrekey(int id) async {
+    opks.remove(id);
+
+    // Generate a new unique id for the OPK.
+    while (true) {
+      final newId = generateRandom32BitNumber();
+      if (opks.containsKey(newId)) {
+        continue;
+      }
+
+      opks[newId] = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
+      break;
+    }
+
+    return OmemoDevice(
       jid,
-      id,
+      this.id,
       ik,
       spk,
       spkId,
@@ -145,12 +110,12 @@ 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 +131,8 @@ 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() {
-    return Device(
+  OmemoDevice withNewId() {
+    return OmemoDevice(
       jid,
       generateRandom32BitNumber(),
       ik,
@@ -179,7 +144,7 @@ class Device {
       opks,
     );
   }
-  
+
   /// Converts this device into an OmemoBundle that could be used for publishing.
   Future<OmemoBundle> toBundle() async {
     final encodedOpks = <int, String>{};
@@ -199,43 +164,24 @@ class Device {
     );
   }
 
-  /// Serialise the device information.
-  Future<Map<String, dynamic>> toJson() async {
-    /// Serialise the OPKs
-    final serialisedOpks = List<Map<String, dynamic>>.empty(growable: true);
-    for (final entry in opks.entries) {
-      serialisedOpks.add({
-        'id': entry.key,
-        'public': base64.encode(await entry.value.pk.getBytes()),
-        'private': base64.encode(await entry.value.sk.getBytes()),
-      });
-    }
-    
-    return {
-      'jid': jid,
-      'id': id,
-      'ik': base64.encode(await ik.sk.getBytes()),
-      'ik_pub': base64.encode(await ik.pk.getBytes()),
-      'spk': base64.encode(await spk.sk.getBytes()),
-      'spk_pub': base64.encode(await spk.pk.getBytes()),
-      'spk_id': spkId,
-      'spk_sig': base64.encode(spkSignature),
-      'old_spk': base64EncodeIfNotNull(await oldSpk?.sk.getBytes()),
-      'old_spk_pub': base64EncodeIfNotNull(await oldSpk?.pk.getBytes()),
-      'old_spk_id': oldSpkId,
-      'opks': serialisedOpks,
-    };
+  /// 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());
   }
 
   @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;
         }
@@ -247,15 +193,18 @@ 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 &&
-      oldSpkMatch &&
-      jid == other.jid &&
-      listsEqual(spkSignature, other.spkSignature) &&
-      spkId == other.spkId &&
-      oldSpkId == other.oldSpkId &&
-      opksMatch;
+        ikMatch &&
+        spkMatch &&
+        oldSpkMatch &&
+        jid == other.jid &&
+        listsEqual(spkSignature, other.spkSignature) &&
+        spkId == other.spkId &&
+        oldSpkId == other.oldSpkId &&
+        opksMatch;
   }
 }

lib/src/omemo/encrypted_key.dart

@@ -1,13 +1,23 @@
+import 'dart:convert';
+
 import 'package:meta/meta.dart';
 
 /// EncryptedKey is the intermediary format of a <key /> element in the OMEMO message's
 /// <keys /> header.
 @immutable
 class EncryptedKey {
+  const EncryptedKey(this.rid, this.value, this.kex);
 
-  const EncryptedKey(this.jid, this.rid, this.value, this.kex);
-  final String jid;
+  /// The id of the device the key is encrypted for.
   final int rid;
+
+  /// The base64-encoded payload.
   final String value;
+
+  /// Flag indicating whether the payload is a OMEMOKeyExchange (true) or
+  /// an OMEMOAuthenticatedMessage (false).
   final bool kex;
+
+  /// The base64-decoded payload.
+  List<int> get data => base64Decode(value);
 }

lib/src/omemo/encryption_result.dart

@@ -1,15 +1,36 @@
 import 'package:meta/meta.dart';
 import 'package:omemo_dart/src/omemo/encrypted_key.dart';
+import 'package:omemo_dart/src/omemo/errors.dart';
 
 @immutable
 class EncryptionResult {
+  const EncryptionResult(
+    this.ciphertext,
+    this.encryptedKeys,
+    this.deviceEncryptionErrors,
+    this.newRatchets,
+    this.replacedRatchets,
+    this.canSend,
+  );
 
-  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
-  final List<EncryptedKey> encryptedKeys;
+  /// for the ratchet with said device Id.
+  final Map<String, List<EncryptedKey>> encryptedKeys;
+
+  /// Mapping of a JID to
+  final Map<String, List<EncryptToJidError>> deviceEncryptionErrors;
+
+  /// Mapping of JIDs to a list of device ids for which we created a new ratchet session.
+  final Map<String, List<int>> newRatchets;
+
+  /// Similar to [newRatchets], but the ratchets listed in [replacedRatchets] where also existent before
+  /// and replaced with the new ratchet.
+  final Map<String, List<int>> replacedRatchets;
+
+  /// A flag indicating that the message could be sent like that, i.e. we were able
+  /// to encrypt to at-least one device per recipient.
+  final bool canSend;
 }

lib/src/omemo/errors.dart

@@ -0,0 +1,12 @@
+import 'package:omemo_dart/src/errors.dart';
+
+/// Returned on encryption, if encryption failed for some reason.
+class EncryptToJidError extends OmemoError {
+  EncryptToJidError(this.device, this.error);
+
+  /// The device the error occurred with
+  final int? device;
+
+  /// The actual error.
+  final OmemoError error;
+}

lib/src/omemo/events.dart

@@ -1,36 +0,0 @@
-import 'package:omemo_dart/src/double_ratchet/double_ratchet.dart';
-import 'package:omemo_dart/src/omemo/device.dart';
-
-abstract class OmemoEvent {}
-
-/// Triggered when a ratchet has been modified
-class RatchetModifiedEvent extends OmemoEvent {
-
-  RatchetModifiedEvent(this.jid, this.deviceId, this.ratchet);
-  final String jid;
-  final int deviceId;
-  final OmemoDoubleRatchet ratchet;
-}
-
-/// 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 {
-
-  DeviceMapModifiedEvent(this.map);
-  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;
-}

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;
@@ -10,8 +9,8 @@ class DeviceFingerprint {
   @override
   bool operator ==(Object other) {
     return other is DeviceFingerprint &&
-      fingerprint == other.fingerprint &&
-      deviceId == other.deviceId;
+        fingerprint == other.fingerprint &&
+        deviceId == other.deviceId;
   }
 
   @override

lib/src/omemo/queue.dart

@@ -0,0 +1,100 @@
+import 'dart:async';
+import 'dart:collection';
+
+import 'package:meta/meta.dart';
+import 'package:synchronized/synchronized.dart';
+
+extension UtilAllMethodsList<T> on List<T> {
+  void removeAll(List<T> values) {
+    for (final value in values) {
+      remove(value);
+    }
+  }
+
+  bool containsAll(List<T> values) {
+    for (final value in values) {
+      if (!contains(value)) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+}
+
+class _RatchetAccessQueueEntry {
+  _RatchetAccessQueueEntry(
+    this.jids,
+    this.completer,
+  );
+
+  final List<String> jids;
+  final Completer<void> completer;
+}
+
+class RatchetAccessQueue {
+  final Queue<_RatchetAccessQueueEntry> _queue = Queue();
+
+  @visibleForTesting
+  final List<String> runningOperations = List<String>.empty(growable: true);
+
+  final Lock lock = Lock();
+
+  bool canBypass(List<String> jids) {
+    for (final jid in jids) {
+      if (runningOperations.contains(jid)) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+
+  Future<void> enterCriticalSection(List<String> jids) async {
+    final completer = await lock.synchronized<Completer<void>?>(() {
+      if (canBypass(jids)) {
+        runningOperations.addAll(jids);
+        return null;
+      }
+
+      final completer = Completer<void>();
+      _queue.add(
+        _RatchetAccessQueueEntry(
+          jids,
+          completer,
+        ),
+      );
+
+      return completer;
+    });
+
+    await completer?.future;
+  }
+
+  Future<void> leaveCriticalSection(List<String> jids) async {
+    await lock.synchronized(() {
+      runningOperations.removeAll(jids);
+
+      while (_queue.isNotEmpty) {
+        if (canBypass(_queue.first.jids)) {
+          final head = _queue.removeFirst();
+          runningOperations.addAll(head.jids);
+          head.completer.complete();
+        } else {
+          break;
+        }
+      }
+    });
+  }
+
+  Future<T> synchronized<T>(
+    List<String> jids,
+    Future<T> Function() function,
+  ) async {
+    await enterCriticalSection(jids);
+    final result = await function();
+    await leaveCriticalSection(jids);
+
+    return result;
+  }
+}

lib/src/omemo/ratchet_data.dart

@@ -0,0 +1,18 @@
+import 'package:omemo_dart/src/double_ratchet/double_ratchet.dart';
+
+class OmemoRatchetData {
+  const OmemoRatchetData(
+    this.jid,
+    this.id,
+    this.ratchet,
+  );
+
+  /// The JID we have the ratchet with.
+  final String jid;
+
+  /// The device id we have the ratchet with.
+  final int id;
+
+  /// The actual double ratchet to commit.
+  final OmemoDoubleRatchet ratchet;
+}

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.keys,
+    this.payload,
+    this.isCatchup,
+  );
+
+  /// The bare JID of the sender of the stanza.
+  final String bareSenderJid;
+
+  /// The device ID of the sender.
+  final int senderDeviceId;
+
+  /// The included encrypted keys for our own JID
+  final List<EncryptedKey> keys;
+
+  /// The string payload included in the <encrypted /> element.
+  final String? payload;
+
+  /// Flag indicating whether the message was received due to a catchup.
+  final bool isCatchup;
+}
+
+/// 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

@@ -1,39 +0,0 @@
-import 'package:omemo_dart/src/helpers.dart';
-import 'package:omemo_dart/src/protobuf/protobuf.dart';
-
-class OmemoAuthenticatedMessage {
-
-  OmemoAuthenticatedMessage();
-
-  factory OmemoAuthenticatedMessage.fromBuffer(List<int> data) {
-    var i = 0;
-    
-    // required bytes mac     = 1;
-    if (data[0] != fieldId(1, fieldTypeByteArray)) {
-      throw Exception();
-    }
-    final mac = data.sublist(2, i + 2 + data[1]);
-    i += data[1] + 2;
-
-    if (data[i] != fieldId(2, fieldTypeByteArray)) {
-      throw Exception();
-    }
-    final message = data.sublist(i + 2, i + 2 + data[i + 1]);
-
-    return OmemoAuthenticatedMessage()
-      ..mac = mac
-      ..message = message;
-  }
-  
-  List<int>? mac;
-  List<int>? message;
-
-  List<int> writeToBuffer() {
-    return concat([
-      [fieldId(1, fieldTypeByteArray), mac!.length],
-      mac!,
-      [fieldId(2, fieldTypeByteArray), message!.length],
-      message!,
-    ]);
-  }
-}

lib/src/protobuf/omemo_key_exchange.dart

@@ -1,72 +0,0 @@
-import 'package:omemo_dart/src/helpers.dart';
-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) {
-    var i = 0;
-
-    if (data[i] != fieldId(1, fieldTypeUint32)) {
-      throw Exception();
-    }
-    var decoded = decodeVarint(data, 1);
-    final pkId = decoded.n;
-    i += decoded.length + 1;
-
-    if (data[i] != fieldId(2, fieldTypeUint32)) {
-      throw Exception();
-    }
-    decoded = decodeVarint(data, i + 1);
-    final spkId = decoded.n;
-    i += decoded.length + 1;
-
-    if (data[i] != fieldId(3, fieldTypeByteArray)) {
-      throw Exception();
-    }
-    final ik = data.sublist(i + 2, i + 2 + data[i + 1]);
-    i += 2 + data[i + 1];
-
-    if (data[i] != fieldId(4, fieldTypeByteArray)) {
-      throw Exception();
-    }
-    final ek = data.sublist(i + 2, i + 2 + data[i + 1]);
-    i += 2 + data[i + 1];
-
-    if (data[i] != fieldId(5, fieldTypeByteArray)) {
-      throw Exception();
-    }
-    final message = OmemoAuthenticatedMessage.fromBuffer(data.sublist(i + 2));
-
-    return OmemoKeyExchange()
-      ..pkId = pkId
-      ..spkId = spkId
-      ..ik = ik
-      ..ek = ek
-      ..message = message;
-  }
-  
-  int? pkId;
-  int? spkId;
-  List<int>? ik;
-  List<int>? ek;
-  OmemoAuthenticatedMessage? message;
-
-  List<int> writeToBuffer() {
-    final msg = message!.writeToBuffer();
-    return concat([
-      [fieldId(1, fieldTypeUint32)],
-      encodeVarint(pkId!),
-      [fieldId(2, fieldTypeUint32)],
-      encodeVarint(spkId!),
-      [fieldId(3, fieldTypeByteArray), ik!.length],
-      ik!,
-      [fieldId(4, fieldTypeByteArray), ek!.length],
-      ek!,
-      [fieldId(5, fieldTypeByteArray), msg.length],
-      msg,
-    ]);
-  }
-}

lib/src/protobuf/omemo_message.dart

@@ -1,76 +0,0 @@
-import 'package:omemo_dart/src/helpers.dart';
-import 'package:omemo_dart/src/protobuf/protobuf.dart';
-
-class OmemoMessage {
-
-  OmemoMessage();
-
-  factory OmemoMessage.fromBuffer(List<int> data) {
-    var i = 0;
-    
-    // required uint32 n          = 1;
-    if (data[0] != fieldId(1, fieldTypeUint32)) {
-      throw Exception();
-    }
-    var decode = decodeVarint(data, 1);
-    final n = decode.n;
-    i += decode.length + 1;
-
-    // required uint32 pn         = 2;
-    if (data[i] != fieldId(2, fieldTypeUint32)) {
-      throw Exception();
-    }
-    decode = decodeVarint(data, i + 1);
-    final pn = decode.n;
-    i += decode.length + 1;
-
-    // required bytes  dh_pub     = 3;
-    if (data[i] != fieldId(3, fieldTypeByteArray)) {
-      throw Exception();
-    }
-    final dhPub = data.sublist(i + 2, i + 2 + data[i + 1]);
-    i += 2 + data[i + 1];
-
-    // optional bytes  ciphertext = 4;
-    List<int>? ciphertext;
-    if (i < data.length) {
-      if (data[i] != fieldId(4, fieldTypeByteArray)) {
-        throw Exception();
-      }
-
-      ciphertext = data.sublist(i + 2, i + 2 + data[i + 1]);
-    }
-
-    return OmemoMessage()
-      ..n = n
-      ..pn = pn
-      ..dhPub = dhPub
-      ..ciphertext = ciphertext;
-  }
-
-  int? n;
-  int? pn;
-  List<int>? dhPub;
-  List<int>? ciphertext;
-
-  List<int> writeToBuffer() {
-    final data = concat([
-      [fieldId(1, fieldTypeUint32)],
-      encodeVarint(n!),
-      [fieldId(2, fieldTypeUint32)],
-      encodeVarint(pn!),
-      [fieldId(3, fieldTypeByteArray), dhPub!.length],
-      dhPub!,
-    ]);
-
-    if (ciphertext != null) {
-      return concat([
-        data,
-        [fieldId(4, fieldTypeByteArray), ciphertext!.length],
-        ciphertext!,
-      ]);
-    }
-
-    return data;
-  }
-}

lib/src/protobuf/protobuf.dart

@@ -1,68 +0,0 @@
-/// Masks the 7 LSB
-const lsb7Mask = 0x7F;
-
-/// Constant for setting the MSB
-const msb = 1 << 7;
-
-/// Field types
-const fieldTypeUint32 = 0;
-const fieldTypeByteArray = 2;
-
-int fieldId(int number, int type) {
-  return (number << 3) | type;
-}
-
-class VarintDecode {
-
-  const VarintDecode(this.n, this.length);
-  final int n;
-  final int length;
-}
-
-/// Decode a Varint that begins at [input]'s index [offset].
-VarintDecode decodeVarint(List<int> input, int offset) {
-  // The return value
-  var n = 0;
-  // The byte offset counter
-  var i = 0;
-
-  // Iterate until the MSB of the byte is 0
-  while (true) {
-    // Mask only the 7 LSB and "move" them accordingly
-    n += (input[offset + i] & lsb7Mask) << (7 * i);
-
-    // Break if we reached the end
-    if (input[offset + i] & 1 << 7 == 0) {
-      break;
-    }
-    i++;
-  }
-
-  return VarintDecode(n, i + 1);
-}
-
-// Encodes the integer [i] into a Varint.
-List<int> encodeVarint(int i) {
-  assert(i >= 0, "Two's complement is not implemented");
-  final ret = List<int>.empty(growable: true);
-
-  var j = 0;
-  while (true) {
-    // 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 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++;
-    }
-  }
-
-  return ret;
-}

lib/src/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/src/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/src/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/src/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/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<void> loadTrustData(String jid) async {}
 }

lib/src/trust/base.dart

@@ -1,3 +1,5 @@
+import 'package:meta/meta.dart';
+
 /// The base class for managing trust in OMEMO sessions.
 // ignore: one_member_abstracts
 abstract class TrustManager {
@@ -7,5 +9,25 @@ 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].
+  @internal
   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);
+
+  /// Removes all trust decisions for [jid].
+  @internal
+  Future<void> removeTrustDecisionsForJid(String jid);
+
+  // ignore: comment_references
+  /// Called from within the [OmemoManager].
+  /// Loads the trust data for the JID [jid] from persistent storage
+  /// into the internal cache, if applicable.
+  @internal
+  Future<void> loadTrustData(String jid);
 }

lib/src/trust/btbv.dart

@@ -1,36 +1,116 @@
 import 'package:meta/meta.dart';
+import 'package:omemo_dart/src/helpers.dart';
 import 'package:omemo_dart/src/omemo/ratchet_map_key.dart';
 import 'package:omemo_dart/src/trust/base.dart';
-import 'package:synchronized/synchronized.dart';
+
+@immutable
+class BTBVTrustData {
+  const BTBVTrustData(
+    this.jid,
+    this.device,
+    this.state,
+    this.enabled,
+    this.trusted,
+  );
+
+  /// The JID in question.
+  final String jid;
+
+  /// The device (ratchet) in question.
+  final int device;
+
+  /// The trust state of the ratchet.
+  final BTBVTrustState state;
+
+  /// Flag indicating whether the ratchet is enabled (true) or not (false).
+  final bool enabled;
+
+  /// Flag indicating whether the ratchet is trusted. For loading and commiting a ratchet, this field
+  /// contains an arbitrary value.
+  /// When using [BlindTrustBeforeVerificationTrustManager.getDevicesTrust], this flag will be true if
+  /// the ratchet is trusted and false if not.
+  final bool trusted;
+}
+
+/// A callback for when a trust decision is to be commited to persistent storage.
+typedef BTBVTrustCommitCallback = Future<void> Function(BTBVTrustData data);
+
+/// A stub-implementation of [BTBVTrustCommitCallback].
+Future<void> btbvCommitStub(BTBVTrustData _) async {}
+
+/// A callback for when all trust decisions for a JID should be removed from persistent storage.
+typedef BTBVRemoveTrustForJidCallback = Future<void> Function(String jid);
+
+/// A stub-implementation of [BTBVRemoveTrustForJidCallback].
+Future<void> btbvRemoveTrustStub(String _) async {}
+
+/// A callback for when trust data should be loaded.
+typedef BTBVLoadDataCallback = Future<List<BTBVTrustData>> Function(String jid);
+
+/// A stub-implementation for [BTBVLoadDataCallback].
+Future<List<BTBVTrustData>> btbvLoadDataStub(String _) async => [];
 
 /// Every device is in either of those two trust states:
 /// - notTrusted: The device is absolutely not trusted
 /// - blindTrust: The fingerprint is not verified using OOB means
 /// - verified: The fingerprint has been verified using OOB means
 enum BTBVTrustState {
-  notTrusted,
-  blindTrust,
-  verified,
+  notTrusted(1),
+  blindTrust(2),
+  verified(3);
+
+  const BTBVTrustState(this.value);
+
+  factory BTBVTrustState.fromInt(int value) {
+    switch (value) {
+      case 1:
+        return BTBVTrustState.notTrusted;
+      case 2:
+        return BTBVTrustState.blindTrust;
+      case 3:
+        return BTBVTrustState.verified;
+      // TODO(Unknown): Should we handle this better?
+      default:
+        return BTBVTrustState.notTrusted;
+    }
+  }
+
+  /// The value backing the trust state.
+  final int value;
 }
 
 /// 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()
-    : trustCache = {},
-      devices = {},
-      _lock = Lock();
+class BlindTrustBeforeVerificationTrustManager extends TrustManager {
+  BlindTrustBeforeVerificationTrustManager({
+    this.loadData = btbvLoadDataStub,
+    this.commit = btbvCommitStub,
+    this.removeTrust = btbvRemoveTrustStub,
+  });
 
-  /// 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;
+  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;
+  final Map<String, List<int>> devices = {};
 
-  /// The lock for devices and trustCache
-  final Lock _lock;
+  /// Callback for loading trust data.
+  final BTBVLoadDataCallback loadData;
+
+  /// Callback for commiting trust data to persistent storage.
+  final BTBVTrustCommitCallback commit;
+
+  /// Callback for removing trust data for a JID.
+  final BTBVRemoveTrustForJidCallback removeTrust;
 
   /// Returns true if [jid] has at least one device that is verified. If not, returns false.
   /// Note that this function accesses devices and trustCache, which requires that the
@@ -42,98 +122,148 @@ abstract class BlindTrustBeforeVerificationTrustManager extends TrustManager {
       return trustCache[RatchetMapKey(jid, id)]! == BTBVTrustState.verified;
     });
   }
-  
+
   @override
   Future<bool> isTrusted(String jid, int deviceId) async {
-    var returnValue = false;
-    await _lock.synchronized(() async {
-      final trustCacheValue = trustCache[RatchetMapKey(jid, deviceId)];
-      if (trustCacheValue == BTBVTrustState.notTrusted) {
-        returnValue = false;
-        return;
-      } else if (trustCacheValue == BTBVTrustState.verified) {
-        // The key is verified, so it's safe.
-        returnValue = true;
-        return;
+    final trustCacheValue = trustCache[RatchetMapKey(jid, deviceId)];
+    if (trustCacheValue == BTBVTrustState.notTrusted) {
+      return false;
+    } else if (trustCacheValue == BTBVTrustState.verified) {
+      // The key is verified, so it's safe.
+      return true;
+    } else {
+      if (_hasAtLeastOneVerifiedDevice(jid)) {
+        // Do not trust if there is at least one device with full trust
+        return false;
       } else {
-        if (_hasAtLeastOneVerifiedDevice(jid)) {
-          // Do not trust if there is at least one device with full trust
-          returnValue = false;
-          return;
-        } else {
-          // We have not verified a key from [jid], so it is blind trust all the way.
-          returnValue = true;
-          return;
-        }
+        // We have not verified a key from [jid], so it is blind trust all the way.
+        return true;
       }
-    });
-
-    return returnValue;
+    }
   }
 
   @override
   Future<void> onNewSession(String jid, int deviceId) async {
-    await _lock.synchronized(() async {
-      if (_hasAtLeastOneVerifiedDevice(jid)) {
-        trustCache[RatchetMapKey(jid, deviceId)] = BTBVTrustState.notTrusted;
-      } else {
-        trustCache[RatchetMapKey(jid, deviceId)] = BTBVTrustState.blindTrust;
-      }
+    final key = RatchetMapKey(jid, deviceId);
+    if (_hasAtLeastOneVerifiedDevice(jid)) {
+      trustCache[key] = BTBVTrustState.notTrusted;
+      enablementCache[key] = false;
+    } else {
+      trustCache[key] = BTBVTrustState.blindTrust;
+      enablementCache[key] = true;
+    }
 
-      if (devices.containsKey(jid)) {
-        devices[jid]!.add(deviceId);
-      } else {
-        devices[jid] = List<int>.from([deviceId]);
-      }
+    // Append to the device list
+    devices.appendOrCreate(jid, deviceId, checkExistence: true);
 
-      // Commit the state
-      await commitState();
-    });
+    // Commit the state
+    await commit(
+      BTBVTrustData(
+        jid,
+        deviceId,
+        trustCache[key]!,
+        enablementCache[key]!,
+        false,
+      ),
+    );
   }
-  
-  /// Returns a mapping from the device identifiers of [jid] to their trust state.
-  Future<Map<int, BTBVTrustState>> getDevicesTrust(String jid) async {
-    final map = <int, BTBVTrustState>{};
 
-    await _lock.synchronized(() async {
-      for (final deviceId in devices[jid]!) {
-        map[deviceId] = trustCache[RatchetMapKey(jid, deviceId)]!;
+  /// 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, BTBVTrustData>> getDevicesTrust(String jid) async {
+    final map = <int, BTBVTrustData>{};
+
+    if (!devices.containsKey(jid)) return map;
+
+    for (final deviceId in devices[jid]!) {
+      final key = RatchetMapKey(jid, deviceId);
+      if (!trustCache.containsKey(key) || !enablementCache.containsKey(key)) {
+        continue;
       }
-    });
+
+      map[deviceId] = BTBVTrustData(
+        jid,
+        deviceId,
+        trustCache[key]!,
+        enablementCache[key]!,
+        await isTrusted(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 {
-    await _lock.synchronized(() async {
-      trustCache[RatchetMapKey(jid, deviceId)] = state;
+  Future<void> setDeviceTrust(
+    String jid,
+    int deviceId,
+    BTBVTrustState state,
+  ) async {
+    final key = RatchetMapKey(jid, deviceId);
+    trustCache[key] = state;
 
-      // Commit the state
-      await commitState();
-    });
+    // Commit the state
+    await commit(
+      BTBVTrustData(
+        jid,
+        deviceId,
+        state,
+        enablementCache[key]!,
+        false,
+      ),
+    );
   }
 
-  /// 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();
+  @override
+  Future<bool> isEnabled(String jid, int deviceId) 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 {
+    final key = RatchetMapKey(jid, deviceId);
+    enablementCache[key] = enabled;
+
+    // Commit the state
+    await commit(
+      BTBVTrustData(
+        jid,
+        deviceId,
+        trustCache[key]!,
+        enabled,
+        false,
+      ),
+    );
+  }
+
+  @override
+  Future<void> removeTrustDecisionsForJid(String jid) async {
+    // Clear the caches
+    for (final device in devices[jid]!) {
+      final key = RatchetMapKey(jid, device);
+      trustCache.remove(key);
+      enablementCache.remove(key);
+    }
+    devices.remove(jid);
+
+    // Commit the state
+    await removeTrust(jid);
+  }
+
+  @override
+  Future<void> loadTrustData(String jid) async {
+    for (final result in await loadData(jid)) {
+      final key = RatchetMapKey(jid, result.device);
+      trustCache[key] = result.state;
+      enablementCache[key] = result.enabled;
+      devices.appendOrCreate(jid, result.device, checkExistence: true);
+    }
+  }
 
-  /// 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)]!;
-}
-
-/// A BTBV TrustManager that does not commit its state to persistent storage. Well suited
-/// for testing.
-class MemoryBTBVTrustManager extends BlindTrustBeforeVerificationTrustManager {
-  @override
-  Future<void> commitState() async {}
-
-  @override
-  Future<void> loadState() async {}
+  BTBVTrustState getDeviceTrust(String jid, int deviceId) =>
+      trustCache[RatchetMapKey(jid, deviceId)]!;
 }

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<void> loadTrustData(String jid) async {}
 }

lib/src/x3dh/x3dh.dart

@@ -1,18 +1,16 @@
 import 'dart:convert';
 import 'dart:math';
 import 'package:cryptography/cryptography.dart';
+import 'package:moxlib/moxlib.dart';
+import 'package:omemo_dart/src/common/constants.dart';
 import 'package:omemo_dart/src/crypto.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';
 
-/// The overarching assumption is that we use Ed25519 keys for the identity keys
-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 +20,6 @@ class X3DHAliceResult {
 
 /// Received by Bob
 class X3DHMessage {
-
   const X3DHMessage(this.ik, this.ek, this.opkId);
   final OmemoPublicKey ik;
   final OmemoPublicKey ek;
@@ -30,7 +27,6 @@ class X3DHMessage {
 }
 
 class X3DHBobResult {
-
   const X3DHBobResult(this.sk, this.ad);
   final List<int> sk;
   final List<int> ad;
@@ -39,7 +35,10 @@ 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 +69,11 @@ 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<Result<InvalidKeyExchangeSignatureError, X3DHAliceResult>>
+    x3dhFromBundle(
+  OmemoBundle bundle,
+  OmemoKeyPair ik,
+) async {
   // Check the signature first
   final signatureValue = await Ed25519().verify(
     await bundle.spk.getBytes(),
@@ -81,7 +84,7 @@ Future<X3DHAliceResult> x3dhFromBundle(OmemoBundle bundle, OmemoKeyPair ik) asyn
   );
 
   if (!signatureValue) {
-    throw InvalidSignatureException();
+    return Result(InvalidKeyExchangeSignatureError());
   }
 
   // Generate EK
@@ -91,9 +94,9 @@ Future<X3DHAliceResult> x3dhFromBundle(OmemoBundle bundle, OmemoKeyPair ik) asyn
   final opkIndex = random.nextInt(bundle.opksEncoded.length);
   final opkId = bundle.opksEncoded.keys.elementAt(opkIndex);
   final opk = bundle.getOpk(opkId);
-  
+
   final dh1 = await omemoDH(ik, bundle.spk, 1);
-  final dh2 = await omemoDH(ek, bundle.ik,  2);
+  final dh2 = await omemoDH(ek, bundle.ik, 2);
   final dh3 = await omemoDH(ek, bundle.spk, 0);
   final dh4 = await omemoDH(ek, opk, 0);
 
@@ -103,14 +106,19 @@ Future<X3DHAliceResult> x3dhFromBundle(OmemoBundle bundle, OmemoKeyPair ik) asyn
     await bundle.ik.getBytes(),
   ]);
 
-  return X3DHAliceResult(ek, sk, opkId, ad);
+  return Result(X3DHAliceResult(ek, sk, opkId, ad));
 }
 
 /// 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 dh2 = await omemoDH(ik, msg.ek, 1);
   final dh3 = await omemoDH(spk, msg.ek, 0);
   final dh4 = await omemoDH(opk, msg.ek, 0);
 

omemo_dart.doap

@@ -0,0 +1,53 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<rdf:RDF xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'
+         xmlns="http://usefulinc.com/ns/doap#"
+         xmlns:foaf="http://xmlns.com/foaf/0.1/"
+         xmlns:xmpp="https://linkmauve.fr/ns/xmpp-doap#"
+         xmlns:schema="https://schema.org/">
+  <Project xml:lang='en'>
+    <!-- Moxxy information -->
+    <name>omemo_dart</name>
+    <created>2022-06-30</created>
+    <homepage rdf:resource="https://github.com/PapaTutuWawa/omemo_dart" />
+    <os>Linux</os>
+    <os>Windows</os>
+    <os>macOS</os>
+    <os>Android</os>
+    <os>iOS</os>
+
+    <!-- Description -->
+    <shortdesc xml:lang="de">A Dart implementation of the cryptography needed for OMEMO 0.8.3</shortdesc>
+    <description xml:lang="en">omemo_dart is a pure Dart implementation of the low-level components (X3DH, Double Ratchet) with a high-level library-agnostic interface for implementing OMEMO 0.8.3.</description>
+
+    <!-- Maintainer information -->
+    <maintainer>
+      <foaf:Person>
+      	<foaf:name>Alexander "Polynomdivision"</foaf:name>
+      	<foaf:homepage rdf:resource="https://polynom.me" />
+      </foaf:Person>
+    </maintainer>
+
+    <!-- Channel list -->
+    <developer-forum rdf:resource='xmpp:dev@muc.moxxy.org?join'/>
+
+    <!-- Repository information -->
+    <programming-language>Dart</programming-language>
+    <bug-database rdf:resource="https://github.com/PapaTutuWawa/omemo_dart/issues" />
+    <license rdf:resource="https://github.com/PapaTutuWawa/omemo_dart/blob/master/LICENSE" />
+    <repository>
+      <GitRepository>
+        <browse rdf:resource="https://github.com/PapaTutuWawa/omemo_dart" />
+        <location rdf:resource="https://github.com/PapaTutuWawa/omemo_dart.git" />
+      </GitRepository>
+    </repository>
+
+    <!-- XEP list -->
+    <implements>
+      <xmpp:SupportedXep>
+        <xmpp:xep rdf:resource="https://xmpp.org/extensions/xep-0384.html"/>
+        <xmpp:status>partial</xmpp:status>
+        <xmpp:version>0.8.3</xmpp:version>
+      </xmpp:SupportedXep>
+    </implements>
+  </Project>
+</rdf:RDF>

pubspec.yaml

@@ -1,23 +1,27 @@
 name: omemo_dart
 description: An XMPP library independent OMEMO library
-version: 0.2.0
+version: 0.6.0
 homepage: https://github.com/PapaTutuWawa/omemo_dart
 publish_to: https://git.polynom.me/api/packages/PapaTutuWawa/pub
 
 environment:
-  sdk: '>=2.17.0 <3.0.0'
+  sdk: ">=3.0.0 <4.0.0"
 
 dependencies:
-  collection: ^1.16.0
-  cryptography: ^2.0.5
+  collection: ^1.18.0
+  cryptography: ^2.7.0
   hex: ^0.2.0
-  meta: ^1.8.0
-  pinenacl: ^0.5.1
-  synchronized: ^3.0.0+2
+  logging: ^1.2.0
+  meta: ^1.15.0
+  moxlib:
+    version: ^0.2.0
+    hosted: https://git.polynom.me/api/packages/Moxxy/pub
+  pinenacl: ^0.6.0
+  protobuf: ^3.1.0
+  protoc_plugin: ^21.1.2
+  synchronized: ^3.3.0+3
 
 dev_dependencies:
-  lints: ^2.0.0
-  protobuf: ^2.1.0
-  protoc_plugin: ^20.0.1
-  test: ^1.21.0
-  very_good_analysis: ^3.0.1
+  lints: ^5.0.0
+  test: ^1.25.8
+  very_good_analysis: ^6.0.0

test/double_ratchet_test.dart

@@ -1,39 +1,10 @@
-// ignore_for_file: avoid_print
 import 'dart:convert';
+import 'dart:developer';
 import 'package:cryptography/cryptography.dart';
 import 'package:omemo_dart/omemo_dart.dart';
-import 'package:omemo_dart/protobuf/schema.pb.dart';
-import 'package:omemo_dart/src/double_ratchet/crypto.dart';
 import 'package:test/test.dart';
 
 void main() {
-  test('Test encrypting and decrypting', () async {
-    final sessionAd = List<int>.filled(32, 0x0);
-    final mk = List<int>.filled(32, 0x1);
-    final plaintext = utf8.encode('Hallo');
-    final header = OMEMOMessage()
-      ..n = 0
-      ..pn = 0
-      ..dhPub = List<int>.empty();
-    final asd = concat([sessionAd, header.writeToBuffer()]);
-      
-    final ciphertext = await encrypt(
-      mk,
-      plaintext,
-      asd,
-      sessionAd,
-    );
-
-    final decrypted = await decrypt(
-      mk,
-      ciphertext,
-      asd,
-      sessionAd,
-    );
-
-    expect(decrypted, plaintext);
-  });
-
   test('Test the Double Ratchet', () async {
     // Generate keys
     const bobJid = 'bob@other.example.server';
@@ -55,13 +26,14 @@ void main() {
         2: await opkBob.pk.asBase64(),
       },
     );
-    
+
     // Alice does X3DH
-    final resultAlice = await x3dhFromBundle(bundleBob, ikAlice);
+    final resultAliceRaw = await x3dhFromBundle(bundleBob, ikAlice);
+    final resultAlice = resultAliceRaw.get<X3DHAliceResult>();
 
     // Alice sends the inital message to Bob
     // ...
-    
+
     // Bob does X3DH
     final resultBob = await x3dhFromInitialMessage(
       X3DHMessage(
@@ -74,20 +46,26 @@ void main() {
       ikBob,
     );
 
-    print('X3DH key exchange done');
-
+    log('X3DH key exchange done');
 
     // Alice and Bob now share sk as a common secret and ad
     // Build a session
     final alicesRatchet = await OmemoDoubleRatchet.initiateNewSession(
       spkBob.pk,
+      bundleBob.spkId,
       ikBob.pk,
+      ikAlice.pk,
+      resultAlice.ek.pk,
       resultAlice.sk,
       resultAlice.ad,
+      resultAlice.opkId,
     );
     final bobsRatchet = await OmemoDoubleRatchet.acceptNewSession(
       spkBob,
+      bundleBob.spkId,
       ikAlice.pk,
+      2,
+      resultAlice.ek.pk,
       resultBob.sk,
       resultBob.ad,
     );
@@ -96,39 +74,43 @@ void main() {
 
     for (var i = 0; i < 100; i++) {
       final messageText = 'Hello, dear $i';
-      
+
+      log('${i + 1}/100');
       if (i.isEven) {
         // Alice encrypts a message
-        final aliceRatchetResult = await alicesRatchet.ratchetEncrypt(utf8.encode(messageText));
-        print('Alice sent the message');
+        final aliceRatchetResult =
+            await alicesRatchet.ratchetEncrypt(utf8.encode(messageText));
+        log('Alice sent the message');
 
         // Alice sends it to Bob
         // ...
 
         // Bob tries to decrypt it
         final bobRatchetResult = await bobsRatchet.ratchetDecrypt(
-          aliceRatchetResult.header,
-          aliceRatchetResult.ciphertext,
+          aliceRatchetResult,
         );
-        print('Bob decrypted the message');
+        log('Bob decrypted the message');
 
-        expect(utf8.encode(messageText), bobRatchetResult);
+        expect(bobRatchetResult.isType<List<int>>(), true);
+        expect(bobRatchetResult.get<List<int>>(), utf8.encode(messageText));
       } else {
         // Bob sends a message to Alice
-        final bobRatchetResult = await bobsRatchet.ratchetEncrypt(utf8.encode(messageText));
-        print('Bob sent the message');
+        final bobRatchetResult =
+            await bobsRatchet.ratchetEncrypt(utf8.encode(messageText));
+        log('Bob sent the message');
 
         // Bobs sends it to Alice
         // ...
 
         // Alice tries to decrypt it
         final aliceRatchetResult = await alicesRatchet.ratchetDecrypt(
-          bobRatchetResult.header,
-          bobRatchetResult.ciphertext,
+          bobRatchetResult,
         );
-        print('Alice decrypted the message');
+        log('Alice decrypted the message');
 
-        expect(utf8.encode(messageText), aliceRatchetResult);
+        expect(aliceRatchetResult.isType<List<int>>(), true);
+        expect(aliceRatchetResult.get<List<int>>(), utf8.encode(messageText));
+        expect(utf8.encode(messageText), aliceRatchetResult.get<List<int>>());
       }
     }
   });

test/protobuf_test.dart

@@ -1,174 +0,0 @@
-import 'package:omemo_dart/protobuf/schema.pb.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/protobuf/protobuf.dart';
-import 'package:test/test.dart';
-
-void main() {
-  group('Base 128 Varints', () {
-    test('Test simple parsing of Varints', () {
-      expect(
-        decodeVarint(<int>[1], 0).n,
-        1,
-      );
-      expect(
-        decodeVarint(<int>[1], 0).length,
-        1,
-      );
-      expect(
-        decodeVarint(<int>[0x96, 0x01, 0x00], 0).n,
-        150,
-      );
-      expect(
-        decodeVarint(<int>[0x96, 0x01, 0x00], 0).length,
-        2,
-      );
-      expect(
-        decodeVarint(<int>[172, 2, 0x8], 0).n,
-        300,
-      );
-      expect(
-        decodeVarint(<int>[172, 2, 0x8], 0).length,
-        2,
-      );
-    });
-
-    test('Test encoding Varints', () {
-      expect(
-        encodeVarint(1),
-        <int>[1],
-      );
-      expect(
-        encodeVarint(150),
-        <int>[0x96, 0x01],
-      );
-      expect(
-        encodeVarint(300),
-        <int>[172, 2],
-      );
-    });
-  });
-
-  group('OMEMOMessage', () {
-    test('Decode a OMEMOMessage', () {
-      final pbMessage = OMEMOMessage()
-        ..n = 1
-        ..pn = 5
-        ..dhPub = <int>[1, 2, 3]
-        ..ciphertext = <int>[4, 5, 6];
-      final serial = pbMessage.writeToBuffer();
-      final msg = OmemoMessage.fromBuffer(serial);
-
-      expect(msg.n, 1);
-      expect(msg.pn, 5);
-      expect(msg.dhPub, <int>[1, 2, 3]);
-      expect(msg.ciphertext, <int>[4, 5, 6]);
-    });
-    test('Decode a OMEMOMessage without ciphertext', () {
-      final pbMessage = OMEMOMessage()
-        ..n = 1
-        ..pn = 5
-        ..dhPub = <int>[1, 2, 3];
-      final serial = pbMessage.writeToBuffer();
-      final msg = OmemoMessage.fromBuffer(serial);
-      
-      expect(msg.n, 1);
-      expect(msg.pn, 5);
-      expect(msg.dhPub, <int>[1, 2, 3]);
-      expect(msg.ciphertext, null);
-    });
-    test('Encode a OMEMOMessage', () {
-      final m = OmemoMessage()
-        ..n = 1
-        ..pn = 5
-        ..dhPub = <int>[1, 2, 3]
-        ..ciphertext = <int>[4, 5, 6];
-      final serial = m.writeToBuffer();
-      final msg = OMEMOMessage.fromBuffer(serial);
-      
-      expect(msg.n, 1);
-      expect(msg.pn, 5);
-      expect(msg.dhPub, <int>[1, 2, 3]);
-      expect(msg.ciphertext, <int>[4, 5, 6]);
-    });
-    test('Encode a OMEMOMessage without ciphertext', () {
-      final m = OmemoMessage()
-        ..n = 1
-        ..pn = 5
-        ..dhPub = <int>[1, 2, 3];
-      final serial = m.writeToBuffer();
-      final msg = OMEMOMessage.fromBuffer(serial);
-
-      expect(msg.n, 1);
-      expect(msg.pn, 5);
-      expect(msg.dhPub, <int>[1, 2, 3]);
-      expect(msg.ciphertext, <int>[]);
-    });
-  });
-
-  group('OMEMOAuthenticatedMessage', () {
-    test('Test encoding a message', () {
-      final msg = OmemoAuthenticatedMessage()
-        ..mac = <int>[1, 2, 3]
-        ..message = <int>[4, 5, 6];
-      final decoded = OMEMOAuthenticatedMessage.fromBuffer(msg.writeToBuffer());
-
-      expect(decoded.mac, <int>[1, 2, 3]);
-      expect(decoded.message, <int>[4, 5, 6]);
-    });
-    test('Test decoding a message', () {
-      final msg = OMEMOAuthenticatedMessage()
-        ..mac = <int>[1, 2, 3]
-        ..message = <int>[4, 5, 6];
-      final bytes = msg.writeToBuffer();
-      final decoded = OmemoAuthenticatedMessage.fromBuffer(bytes);
-
-      expect(decoded.mac, <int>[1, 2, 3]);
-      expect(decoded.message, <int>[4, 5, 6]);
-    });
-  });
-
-  group('OMEMOKeyExchange', () {
-    test('Test encoding a message', () {
-      final authMessage = OmemoAuthenticatedMessage()
-        ..mac = <int>[5, 6, 8, 0]
-        ..message = <int>[4, 5, 7, 3, 2];
-      final message = OmemoKeyExchange()
-        ..pkId = 698
-        ..spkId = 245
-        ..ik = <int>[1, 4, 6]
-        ..ek = <int>[4, 6, 7, 80]
-        ..message = authMessage;
-      final kex = OMEMOKeyExchange.fromBuffer(message.writeToBuffer());
-
-      expect(kex.pkId, 698);
-      expect(kex.spkId, 245);
-      expect(kex.ik, <int>[1, 4, 6]);
-      expect(kex.ek, <int>[4, 6, 7, 80]);
-
-      expect(kex.message.mac, <int>[5, 6, 8, 0]);
-      expect(kex.message.message, <int>[4, 5, 7, 3, 2]);
-    });
-    test('Test decoding a message', () {
-      final message = OMEMOAuthenticatedMessage()
-        ..mac = <int>[5, 6, 8, 0]
-        ..message = <int>[4, 5, 7, 3, 2];
-      final kex = OMEMOKeyExchange()
-        ..pkId = 698
-        ..spkId = 245
-        ..ik = <int>[1, 4, 6]
-        ..ek = <int>[4, 6, 7, 80]
-        ..message = message;
-      final decoded = OmemoKeyExchange.fromBuffer(kex.writeToBuffer());
-
-      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.message!.mac, <int>[5, 6, 8, 0]);
-      expect(decoded.message!.message, <int>[4, 5, 7, 3, 2]);
-    });
-  });
-}

test/queue_test.dart

@@ -0,0 +1,62 @@
+import 'dart:async';
+import 'package:omemo_dart/src/omemo/queue.dart';
+import 'package:test/test.dart';
+
+Future<void> testMethod(
+  RatchetAccessQueue queue,
+  List<String> data,
+  int duration,
+) async {
+  await queue.enterCriticalSection(data);
+
+  await Future<void>.delayed(Duration(seconds: duration));
+
+  await queue.leaveCriticalSection(data);
+}
+
+void main() {
+  test('Test blocking due to conflicts', () async {
+    final queue = RatchetAccessQueue();
+
+    unawaited(testMethod(queue, ['a', 'b', 'c'], 5));
+    unawaited(testMethod(queue, ['a'], 4));
+
+    await Future<void>.delayed(const Duration(seconds: 1));
+    expect(
+      queue.runningOperations.containsAll(['a', 'b', 'c']),
+      isTrue,
+    );
+    expect(queue.runningOperations.length, 3);
+
+    await Future<void>.delayed(const Duration(seconds: 4));
+
+    expect(
+      queue.runningOperations.containsAll(['a']),
+      isTrue,
+    );
+    expect(queue.runningOperations.length, 1);
+
+    await Future<void>.delayed(const Duration(seconds: 4));
+    expect(queue.runningOperations.length, 0);
+  });
+
+  test('Test not blocking due to no conflicts', () async {
+    final queue = RatchetAccessQueue();
+
+    unawaited(testMethod(queue, ['a', 'b'], 5));
+    unawaited(testMethod(queue, ['c'], 5));
+    unawaited(testMethod(queue, ['d'], 5));
+
+    await Future<void>.delayed(const Duration(seconds: 1));
+    expect(queue.runningOperations.length, 4);
+    expect(
+      queue.runningOperations.containsAll([
+        'a',
+        'b',
+        'c',
+        'd',
+      ]),
+      isTrue,
+    );
+  });
+}

test/serialisation_test.dart

@@ -1,107 +0,0 @@
-import 'package:omemo_dart/omemo_dart.dart';
-import 'package:omemo_dart/src/trust/always.dart';
-import 'package:test/test.dart';
-
-void main() {
-  test('Test serialising and deserialising the Device', () async {
-    // Generate a random session
-    final oldSession = await OmemoSessionManager.generateNewIdentity(
-      'user@test.server',
-      AlwaysTrustingTrustManager(),
-      opkAmount: 1,
-    );
-    final oldDevice = await oldSession.getDevice();
-    final serialised = await oldDevice.toJson();
-
-    final newDevice = Device.fromJson(serialised);
-    expect(await oldDevice.equals(newDevice), true);
-  });
-
-  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 serialised = await oldDevice.toJson();
-
-    final newDevice = Device.fromJson(serialised);
-    expect(await oldDevice.equals(newDevice), true);
-  });
-  
-  test('Test serialising and deserialising the OmemoDoubleRatchet', () async {
-    // Generate a random ratchet
-    const aliceJid = 'alice@server.example';
-    const bobJid = 'bob@other.server.example';
-    final aliceSession = await OmemoSessionManager.generateNewIdentity(
-      aliceJid,
-      AlwaysTrustingTrustManager(),
-      opkAmount: 1,
-    );
-    final bobSession = await OmemoSessionManager.generateNewIdentity(
-      bobJid,
-      AlwaysTrustingTrustManager(),
-      opkAmount: 1,
-    );
-    final aliceMessage = await aliceSession.encryptToJid(
-      bobJid,
-      'Hello Bob!',
-      newSessions: [
-        await bobSession.getDeviceBundle(),
-      ],
-    );
-    await bobSession.decryptMessage(
-      aliceMessage.ciphertext,
-      aliceJid,
-      await aliceSession.getDeviceId(),
-      aliceMessage.encryptedKeys,
-    );
-    final aliceOld = aliceSession.getRatchet(bobJid, await bobSession.getDeviceId());
-    final aliceSerialised = await aliceOld.toJson();
-    final aliceNew = OmemoDoubleRatchet.fromJson(aliceSerialised);
-
-    expect(await aliceOld.equals(aliceNew), true);
-  });
-
-  test('Test serialising and deserialising the OmemoSessionManager', () async {
-    // Generate a random session
-    final oldSession = await OmemoSessionManager.generateNewIdentity(
-      'a@server',
-      AlwaysTrustingTrustManager(),
-      opkAmount: 4,
-    );
-    final bobSession = await OmemoSessionManager.generateNewIdentity(
-      'b@other.server',
-      AlwaysTrustingTrustManager(),
-      opkAmount: 4,
-    );
-    await oldSession.addSessionFromBundle(
-      'bob@localhost',
-      await bobSession.getDeviceId(),
-      await bobSession.getDeviceBundle(),
-    );
-
-    // Serialise and deserialise
-    final serialised = await oldSession.toJson();
-    final newSession = OmemoSessionManager.fromJson(
-      serialised,
-      AlwaysTrustingTrustManager(),
-    );
-
-    final oldDevice = await oldSession.getDevice();
-    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);
-    for (final session in oldSession.getRatchetMap().entries) {
-      expect(newSession.getRatchetMap().containsKey(session.key), true);
-
-      final oldRatchet = oldSession.getRatchetMap()[session.key]!;
-      final newRatchet = newSession.getRatchetMap()[session.key]!;
-      expect(await oldRatchet.equals(newRatchet), true);
-    }
-  });
-}

test/trust_test.dart

@@ -4,14 +4,15 @@ import 'package:test/test.dart';
 void main() {
   test('Test the Blind Trust Before Verification TrustManager', () async {
     // Caroline's BTBV manager
-    final btbv = MemoryBTBVTrustManager();
+    final btbv = BlindTrustBeforeVerificationTrustManager();
     // Example data
     const aliceJid = 'alice@some.server';
     const bobJid = 'bob@other.server';
-    
+
     // 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

@@ -24,13 +24,14 @@ void main() {
         2: await opkBob.pk.asBase64(),
       },
     );
-    
+
     // Alice does X3DH
-    final resultAlice = await x3dhFromBundle(bundleBob, ikAlice);
+    final resultAliceRaw = await x3dhFromBundle(bundleBob, ikAlice);
+    final resultAlice = resultAliceRaw.get<X3DHAliceResult>();
 
     // Alice sends the inital message to Bob
     // ...
-    
+
     // Bob does X3DH
     final resultBob = await x3dhFromInitialMessage(
       X3DHMessage(
@@ -42,7 +43,7 @@ void main() {
       opkBob,
       ikBob,
     );
-    
+
     expect(resultAlice.sk, resultBob.sk);
     expect(resultAlice.ad, resultBob.ad);
   });
@@ -66,16 +67,9 @@ void main() {
         2: await opkBob.pk.asBase64(),
       },
     );
-    
-    // Alice does X3DH
-    var exception = false;
-    try {
-      await x3dhFromBundle(bundleBob, ikAlice);
-    } catch(e) {
-      exception = true;
-      expect(e is InvalidSignatureException, true, reason: 'Expected InvalidSignatureException, but got $e');
-    }
 
-    expect(exception, true, reason: 'Expected test failure');
+    // Alice does X3DH
+    final result = await x3dhFromBundle(bundleBob, ikAlice);
+    expect(result.isType<InvalidKeyExchangeSignatureError>(), isTrue);
   });
 }