release: Release 0.5.0

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

CHANGELOG.md

@@ -54,3 +54,15 @@
 ## 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

README.md

@@ -28,22 +28,32 @@ Include `omemo_dart` in your `pubspec.yaml` like this:
 dependencies:
   omemo_dart:
     hosted: https://git.polynom.me/api/packages/PapaTutuWawa/pub
-    version: ^0.4.3
+    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`.

analysis_options.yaml

@@ -9,8 +9,5 @@ linter:
 
 analyzer:
   exclude:
-    - "lib/protobuf/*.dart"
-    # TODO: Remove once OmemoSessionManager is gone
-    - "test/omemo_test.dart"
+    - "lib/src/protobuf/*.dart"
     - "example/omemo_dart_example.dart"
-    - "test/serialisation_test.dart"

example/omemo_dart_example.dart

@@ -35,6 +35,10 @@ void main() async {
     // 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
@@ -42,7 +46,7 @@ void main() async {
   // request it using PEP and then convert the device bundle into a OmemoBundle object.
   final bobManager = OmemoManager(
     await OmemoDevice.generateNewDevice(bobJid),
-    MemoryBTBVTrustManager(),
+    BlindTrustBeforeVerificationTrustManager(),
     (result, recipient) async => {},
     (jid) async => [],
     (jid, id) async => null,
@@ -145,6 +149,11 @@ void main() async {
       /// 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,
     ),
   );
 

lib/omemo_dart.dart

@@ -8,9 +8,10 @@ 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/omemomanager.dart';
+export 'src/omemo/omemo.dart';
+export 'src/omemo/ratchet_data.dart';
 export 'src/omemo/ratchet_map_key.dart';
 export 'src/omemo/stanza.dart';
 export 'src/trust/base.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

@@ -1,5 +1,7 @@
 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
@@ -92,7 +94,7 @@ Future<List<int>> aes256CbcEncrypt(
 
 /// 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(
+Future<Result<MalformedCiphertextError, List<int>>> aes256CbcDecrypt(
   List<int> ciphertext,
   List<int> key,
   List<int> iv,
@@ -100,13 +102,19 @@ Future<List<int>> aes256CbcDecrypt(
   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

@@ -1,60 +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

@@ -1,47 +1,24 @@
-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;
-  final int n;
 
-  Future<Map<String, dynamic>> toJson() async {
-    return {
-      'public': base64.encode(await dh.getBytes()),
-      'n': n,
-    };
-  }
+  /// The associated number of the message key we skipped.
+  final int n;
 
   @override
   bool operator ==(Object other) {
@@ -52,6 +29,28 @@ class SkippedKey {
   int get hashCode => dh.hashCode ^ n.hashCode;
 }
 
+@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
@@ -66,77 +65,9 @@ class OmemoDoubleRatchet {
     this.sessionAd,
     this.mkSkipped, // MKSKIPPED
     this.acknowledged,
-    this.kexTimestamp,
     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': null | 'base/64/encoded',
-      'session_ad': 'base/64/encoded',
-      'acknowledged': true | false,
-      'kex_timestamp': int,
-      'kex': 'base/64/encoded',
-      'mkskipped': [
-        {
-          'key': 'base/64/encoded',
-          'public': 'base/64/encoded',
-          'n': 0
-        }, ...
-      ]
-    }
-    */
-    // NOTE: Dart has some issues with just casting a List<dynamic> to List<Map<...>>, as
-    //       such we need to convert the items by hand.
-    final mkSkipped = Map<SkippedKey, List<int>>.fromEntries(
-      (data['mkskipped']! as List<dynamic>)
-          .map<MapEntry<SkippedKey, List<int>>>(
-        (entry) {
-          final map = entry as Map<String, dynamic>;
-          final key = SkippedKey.fromJson(map);
-          return MapEntry(
-            key,
-            base64.decode(map['key']! as String),
-          );
-        },
-      ),
-    );
-
-    return OmemoDoubleRatchet(
-      OmemoKeyPair.fromBytes(
-        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,
-      data['kex_timestamp']! as int,
-      data['kex'] as String?,
-    );
-  }
-
   /// Sending DH keypair
   OmemoKeyPair dhs;
 
@@ -161,16 +92,14 @@ class OmemoDoubleRatchet {
   /// 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 point in time at which we performed the kex exchange to create this ratchet.
-  /// Precision is milliseconds since epoch.
-  int kexTimestamp;
-
   /// The key exchange that was used for initiating the session.
-  final String? kex;
+  final KeyExchangeData kex;
 
   /// Indicates whether we received an empty OMEMO message after building a session with
   /// the device.
@@ -181,21 +110,22 @@ class OmemoDoubleRatchet {
   /// a X3DH. [ik] refers to Bob's (the receiver's) IK public key.
   static Future<OmemoDoubleRatchet> initiateNewSession(
     OmemoPublicKey spk,
+    int spkId,
     OmemoPublicKey ik,
+    OmemoPublicKey ownIk,
+    OmemoPublicKey ek,
     List<int> sk,
     List<int> ad,
-    int timestamp,
+    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,
@@ -204,8 +134,12 @@ class OmemoDoubleRatchet {
       ad,
       {},
       false,
-      timestamp,
-      '',
+      KeyExchangeData(
+        pkId,
+        spkId,
+        ownIk,
+        ek,
+      ),
     );
   }
 
@@ -215,10 +149,12 @@ class OmemoDoubleRatchet {
   /// Alice's (the initiator's) IK public key.
   static Future<OmemoDoubleRatchet> acceptNewSession(
     OmemoKeyPair spk,
+    int spkId,
     OmemoPublicKey ik,
+    int pkId,
+    OmemoPublicKey ek,
     List<int> sk,
     List<int> ad,
-    int kexTimestamp,
   ) async {
     return OmemoDoubleRatchet(
       spk,
@@ -233,72 +169,52 @@ class OmemoDoubleRatchet {
       ad,
       {},
       true,
-      kexTimestamp,
-      null,
+      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,
-      'kex_timestamp': kexTimestamp,
-      'kex': kex,
-    };
-  }
-
-  /// Returns the OMEMO compatible fingerprint of the ratchet session.
-  Future<String> getOmemoFingerprint() async {
-    final curveKey = await ik.toCurve25519();
-    return HEX.encode(await curveKey.getBytes());
-  }
-
-  Future<List<int>?> _trySkippedMessageKeys(
-    OmemoMessage header,
-    List<int> ciphertext,
-  ) async {
-    final key = SkippedKey(
-      OmemoPublicKey.fromBytes(header.dhPub!, KeyPairType.x25519),
-      header.n!,
+  /// 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) {
@@ -306,88 +222,140 @@ 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 = ns;
-    ns = 0;
-    nr = 0;
-    dhr = OmemoPublicKey.fromBytes(header.dhPub!, KeyPairType.x25519);
-
-    final newRk = await kdfRk(rk, await omemoDH(dhs, dhr!, 0));
-    rk = List.from(newRk);
-    ckr = List.from(newRk);
-    dhs = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
-    final newNewRk = await kdfRk(rk, await omemoDH(dhs, dhr!, 0));
-    rk = List.from(newNewRk);
-    cks = List.from(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,
+  /// 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 {
-    // Check if we skipped too many messages
-    final plaintext = await _trySkippedMessageKeys(header, ciphertext);
-    if (plaintext != null) {
-      return plaintext;
+    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!,
-      (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,
@@ -402,27 +370,16 @@ class OmemoDoubleRatchet {
       sessionAd,
       Map<SkippedKey, List<int>>.from(mkSkipped),
       acknowledged,
-      kexTimestamp,
       kex,
     );
   }
 
-  OmemoDoubleRatchet cloneWithKex(String kex) {
-    return OmemoDoubleRatchet(
-      dhs,
-      dhr,
-      rk,
-      cks != null ? List<int>.from(cks!) : null,
-      ckr != null ? List<int>.from(ckr!) : null,
-      ns,
-      nr,
-      pn,
-      ik,
-      sessionAd,
-      Map<SkippedKey, List<int>>.from(mkSkipped),
-      acknowledged,
-      kexTimestamp,
-      kex,
+  /// 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(),
     );
   }
 
@@ -454,7 +411,6 @@ class OmemoDoubleRatchet {
         ns == other.ns &&
         nr == other.nr &&
         pn == other.pn &&
-        listsEqual(sessionAd, other.sessionAd) &&
-        kexTimestamp == other.kexTimestamp;
+        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

@@ -1,61 +1,39 @@
-abstract class OmemoException {}
+abstract class OmemoError {}
 
 /// Triggered during X3DH if the signature if the SPK does verify to the actual SPK.
-class InvalidSignatureException extends OmemoException 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 extends OmemoException 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 extends OmemoException
-    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 extends OmemoException
-    implements Exception {
-  String errMsg() => 'Not encrypted for this device';
-}
-
-/// Triggered by the Session Manager when there is no key for decrypting the message.
-class NoDecryptionKeyException extends OmemoException 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 extends OmemoException implements Exception {
-  String errMsg() => 'Unknown Signed Prekey used.';
-}
-
-/// Triggered by the Session Manager when the received Key Exchange message does not meet
-/// the requirement that a key exchange, given that the ratchet already exists, must be
-/// sent after its creation.
-class InvalidKeyExchangeException extends OmemoException implements Exception {
-  String errMsg() => 'The key exchange was sent before the last kex finished';
-}
-
-/// Triggered by the Session Manager when a message's sequence number is smaller than we
-/// expect it to be.
-class MessageAlreadyDecryptedException extends OmemoException
-    implements Exception {
-  String errMsg() => 'The message has already been decrypted';
-}
+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 NoKeyMaterialAvailableException extends OmemoException
-    implements Exception {
-  String errMsg() =>
-      'No key material available to create a ratchet session with';
+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) {
@@ -43,41 +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,
-  );
-}
-
-int getTimestamp() {
-  return DateTime.now().millisecondsSinceEpoch;
+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/omemo/constants.dart

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

lib/src/omemo/decryption_result.dart

@@ -3,7 +3,15 @@ import 'package:omemo_dart/src/errors.dart';
 
 @immutable
 class DecryptionResult {
-  const DecryptionResult(this.payload, this.error);
+  const DecryptionResult(this.payload, this.usedOpkId, this.error);
+
+  /// The decrypted payload or null, if it was an empty OMEMO message.
   final String? payload;
-  final OmemoException? error;
+
+  /// 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;
+
+  /// The error that occurred during decryption or null, if no error occurred.
+  final OmemoError? error;
 }

lib/src/omemo/device.dart

@@ -22,76 +22,6 @@ class OmemoDevice {
     this.opks,
   );
 
-  /// Deserialize the Device
-  factory OmemoDevice.fromJson(Map<String, dynamic> data) {
-    // NOTE: We use the way OpenSSH names their keys, meaning that ik is the Identity
-    //       Keypair's private key, while ik_pub refers to the Identity Keypair's public
-    //       key.
-    /*
-    {
-      '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'
-        }, ...
-      ]
-    }
-    */
-    // NOTE: Dart has some issues with just casting a List<dynamic> to List<Map<...>>, as
-    //       such we need to convert the items by hand.
-    final opks = Map<int, OmemoKeyPair>.fromEntries(
-      (data['opks']! as List<dynamic>).map<MapEntry<int, OmemoKeyPair>>(
-        (opk) {
-          final map = opk as Map<String, dynamic>;
-          return MapEntry(
-            map['id']! as int,
-            OmemoKeyPair.fromBytes(
-              base64.decode(map['public']! as String),
-              base64.decode(map['private']! as String),
-              KeyPairType.x25519,
-            ),
-          );
-        },
-      ),
-    );
-
-    return OmemoDevice(
-      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<OmemoDevice> generateNewDevice(
     String jid, {
@@ -105,7 +35,16 @@ class OmemoDevice {
 
     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 OmemoDevice(jid, id, ik, spk, spkId, signature, null, null, opks);
@@ -142,7 +81,18 @@ class OmemoDevice {
   /// a new Device object that copies over everything but replaces said key.
   @internal
   Future<OmemoDevice> replaceOnetimePrekey(int id) async {
-    opks[id] = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
+    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,
@@ -221,34 +171,6 @@ class OmemoDevice {
     return HEX.encode(await curveKey.getBytes());
   }
 
-  /// 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,
-    };
-  }
-
   @visibleForTesting
   Future<bool> equals(OmemoDevice other) async {
     var opksMatch = true;

lib/src/omemo/encrypted_key.dart

@@ -1,12 +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.jid, this.rid, this.value, this.kex);
-  final String jid;
+  const EncryptedKey(this.rid, this.value, this.kex);
+
+  /// 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

@@ -1,7 +1,6 @@
 import 'package:meta/meta.dart';
-import 'package:omemo_dart/src/errors.dart';
 import 'package:omemo_dart/src/omemo/encrypted_key.dart';
-import 'package:omemo_dart/src/omemo/ratchet_map_key.dart';
+import 'package:omemo_dart/src/omemo/errors.dart';
 
 @immutable
 class EncryptionResult {
@@ -9,7 +8,7 @@ class EncryptionResult {
     this.ciphertext,
     this.encryptedKeys,
     this.deviceEncryptionErrors,
-    this.jidEncryptionErrors,
+    this.canSend,
   );
 
   /// The actual message that was encrypted.
@@ -17,17 +16,12 @@ class EncryptionResult {
 
   /// Mapping of the device Id to the key for decrypting ciphertext, encrypted
   /// for the ratchet with said device Id.
-  final List<EncryptedKey> encryptedKeys;
+  final Map<String, List<EncryptedKey>> encryptedKeys;
 
-  /// Mapping of a ratchet map keys to a possible exception.
-  final Map<RatchetMapKey, OmemoException> deviceEncryptionErrors;
+  /// Mapping of a JID to
+  final Map<String, List<EncryptToJidError>> deviceEncryptionErrors;
 
-  /// Mapping of a JID to a possible exception.
-  final Map<String, OmemoException> jidEncryptionErrors;
-
-  /// True if the encryption was a success. This means that we could encrypt for
-  /// at least one ratchet.
-  bool isSuccess(int numberOfRecipients) =>
-      encryptedKeys.isNotEmpty &&
-      jidEncryptionErrors.length < numberOfRecipients;
+  /// 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

@@ -1,44 +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,
-    this.added,
-    this.replaced,
-  );
-  final String jid;
-  final int deviceId;
-  final OmemoDoubleRatchet ratchet;
-
-  /// Indicates whether the ratchet has just been created (true) or just modified (false).
-  final bool added;
-
-  /// Indicates whether the ratchet has been replaced (true) or not.
-  final bool replaced;
-}
-
-/// Triggered when a ratchet has been removed and should be removed from storage.
-class RatchetRemovedEvent extends OmemoEvent {
-  RatchetRemovedEvent(this.jid, this.deviceId);
-  final String jid;
-  final int deviceId;
-}
-
-/// Triggered when the device map has been modified
-class DeviceListModifiedEvent extends OmemoEvent {
-  DeviceListModifiedEvent(this.list);
-  final Map<String, List<int>> list;
-}
-
-/// Triggered by the OmemoSessionManager when our own device bundle was modified
-/// and thus should be republished.
-class DeviceModifiedEvent extends OmemoEvent {
-  DeviceModifiedEvent(this.device);
-  final OmemoDevice device;
-}

lib/src/omemo/omemomanager.dart

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

lib/src/omemo/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 +1,26 @@
+import 'package:omemo_dart/src/double_ratchet/double_ratchet.dart';
+
+class OmemoRatchetData {
+  const OmemoRatchetData(
+    this.jid,
+    this.id,
+    this.ratchet,
+    this.added,
+    this.replaced,
+  );
+
+  /// 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;
+
+  /// Indicates whether the ratchet has just been created (true) or just modified (false).
+  final bool added;
+
+  /// Indicates whether the ratchet has been replaced (true) or not.
+  final bool replaced;
+}

lib/src/omemo/stanza.dart

@@ -5,9 +5,9 @@ class OmemoIncomingStanza {
   const OmemoIncomingStanza(
     this.bareSenderJid,
     this.senderDeviceId,
-    this.timestamp,
     this.keys,
     this.payload,
+    this.isCatchup,
   );
 
   /// The bare JID of the sender of the stanza.
@@ -16,14 +16,14 @@ class OmemoIncomingStanza {
   /// The device ID of the sender.
   final int senderDeviceId;
 
-  /// The timestamp when the stanza was received.
-  final int timestamp;
-
-  /// The included encrypted keys
+  /// 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
@@ -37,5 +37,5 @@ class OmemoOutgoingStanza {
   final List<String> recipientJids;
 
   /// The serialised XML data that should be encrypted.
-  final String payload;
+  final String? payload;
 }

lib/src/protobuf/omemo_authenticated_message.dart

@@ -1,38 +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

@@ -1,71 +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

@@ -1,75 +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

@@ -1,64 +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);
-
-  // Thanks to https://github.com/hathibelagal-dev/LEB128 for the trick with toRadixString!
-  final numSevenBlocks = (i.toRadixString(2).length / 7).ceil();
-  for (var j = 0; j < numSevenBlocks; j++) {
-    // The 7 LSB of the byte we're creating
-    final x = (i & (lsb7Mask << j * 7)) >> j * 7;
-
-    if (j == numSevenBlocks - 1) {
-      // If we were to shift further, we only get zero, so we're at the end
-      ret.add(x);
-    } else {
-      // We still have at least one bit more to go, so set the MSB to 1
-      ret.add(x + msb);
-    }
-  }
-
-  return ret;
-}

lib/src/trust/always.dart

@@ -22,5 +22,5 @@ class AlwaysTrustingTrustManager extends TrustManager {
   Future<void> removeTrustDecisionsForJid(String jid) async {}
 
   @override
-  Future<Map<String, dynamic>> toJson() async => <String, dynamic>{};
+  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 {
@@ -7,6 +9,7 @@ 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.
@@ -17,9 +20,14 @@ abstract class TrustManager {
   /// if [enabled] is false.
   Future<void> setEnabled(String jid, int deviceId, bool enabled);
 
-  /// Serialize the trust manager to JSON.
-  Future<Map<String, dynamic>> toJson();
-
   /// Removes all trust decisions for [jid].
+  @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

@@ -1,71 +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, // = 1
-  blindTrust, // = 2
-  verified, // = 3
-}
+  notTrusted(1),
+  blindTrust(2),
+  verified(3);
 
-int _trustToInt(BTBVTrustState state) {
-  switch (state) {
-    case BTBVTrustState.notTrusted:
-      return 1;
-    case BTBVTrustState.blindTrust:
-      return 2;
-    case BTBVTrustState.verified:
-      return 3;
-  }
-}
+  const BTBVTrustState(this.value);
 
-BTBVTrustState _trustFromInt(int i) {
-  switch (i) {
-    case 1:
-      return BTBVTrustState.notTrusted;
-    case 2:
-      return BTBVTrustState.blindTrust;
-    case 3:
-      return BTBVTrustState.verified;
-    default:
-      return BTBVTrustState.notTrusted;
+  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 {
+class BlindTrustBeforeVerificationTrustManager extends TrustManager {
   BlindTrustBeforeVerificationTrustManager({
-    Map<RatchetMapKey, BTBVTrustState>? trustCache,
-    Map<RatchetMapKey, bool>? enablementCache,
-    Map<String, List<int>>? devices,
-  })  : trustCache = trustCache ?? {},
-        enablementCache = enablementCache ?? {},
-        devices = devices ?? {},
-        _lock = Lock();
+    this.loadData = btbvLoadDataStub,
+    this.commit = btbvCommitStub,
+    this.removeTrust = btbvRemoveTrustStub,
+  });
 
   /// 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;
+  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
@@ -80,69 +125,72 @@ abstract class BlindTrustBeforeVerificationTrustManager extends TrustManager {
 
   @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 {
-      final key = RatchetMapKey(jid, deviceId);
-      if (_hasAtLeastOneVerifiedDevice(jid)) {
-        trustCache[key] = BTBVTrustState.notTrusted;
-        enablementCache[key] = false;
-      } else {
-        trustCache[key] = BTBVTrustState.blindTrust;
-        enablementCache[key] = true;
-      }
+    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. If
   /// there are no devices known for [jid], then an empty map is returned.
-  Future<Map<int, BTBVTrustState>> getDevicesTrust(String jid) async {
-    return _lock.synchronized(() async {
-      final map = <int, BTBVTrustState>{};
+  Future<Map<int, BTBVTrustData>> getDevicesTrust(String jid) async {
+    final map = <int, BTBVTrustData>{};
 
-      if (!devices.containsKey(jid)) return map;
+    if (!devices.containsKey(jid)) return map;
 
-      for (final deviceId in devices[jid]!) {
-        map[deviceId] = trustCache[RatchetMapKey(jid, deviceId)]!;
+    for (final deviceId in devices[jid]!) {
+      final key = RatchetMapKey(jid, deviceId);
+      if (!trustCache.containsKey(key) || !enablementCache.containsKey(key)) {
+        continue;
       }
 
-      return map;
-    });
+      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].
@@ -151,108 +199,71 @@ abstract class BlindTrustBeforeVerificationTrustManager extends TrustManager {
     int deviceId,
     BTBVTrustState state,
   ) async {
-    await _lock.synchronized(() async {
-      trustCache[RatchetMapKey(jid, deviceId)] = state;
+    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,
+      ),
+    );
   }
 
   @override
   Future<bool> isEnabled(String jid, int deviceId) async {
-    return _lock.synchronized(() async {
-      final value = enablementCache[RatchetMapKey(jid, deviceId)];
+    final value = enablementCache[RatchetMapKey(jid, deviceId)];
 
-      if (value == null) return false;
-      return value;
-    });
+    if (value == null) return false;
+    return value;
   }
 
   @override
   Future<void> setEnabled(String jid, int deviceId, bool enabled) async {
-    await _lock.synchronized(() async {
-      enablementCache[RatchetMapKey(jid, deviceId)] = enabled;
-    });
+    final key = RatchetMapKey(jid, deviceId);
+    enablementCache[key] = enabled;
 
     // Commit the state
-    await commitState();
-  }
-
-  @override
-  Future<Map<String, dynamic>> toJson() async {
-    return {
-      'devices': devices,
-      'trust': trustCache.map(
-        (key, value) => MapEntry(
-          key.toJsonKey(),
-          _trustToInt(value),
-        ),
-      ),
-      'enable':
-          enablementCache.map((key, value) => MapEntry(key.toJsonKey(), value)),
-    };
-  }
-
-  /// From a serialized version of a BTBV trust manager, extract the device list.
-  /// NOTE: This is needed as Dart cannot just cast a List<dynamic> to List<int> and so on.
-  static Map<String, List<int>> deviceListFromJson(Map<String, dynamic> json) {
-    return (json['devices']! as Map<String, dynamic>).map<String, List<int>>(
-      (key, value) => MapEntry(
-        key,
-        (value as List<dynamic>).map<int>((i) => i as int).toList(),
-      ),
-    );
-  }
-
-  /// From a serialized version of a BTBV trust manager, extract the trust cache.
-  /// NOTE: This is needed as Dart cannot just cast a List<dynamic> to List<int> and so on.
-  static Map<RatchetMapKey, BTBVTrustState> trustCacheFromJson(
-    Map<String, dynamic> json,
-  ) {
-    return (json['trust']! as Map<String, dynamic>)
-        .map<RatchetMapKey, BTBVTrustState>(
-      (key, value) => MapEntry(
-        RatchetMapKey.fromJsonKey(key),
-        _trustFromInt(value as int),
-      ),
-    );
-  }
-
-  /// From a serialized version of a BTBV trust manager, extract the enable cache.
-  /// NOTE: This is needed as Dart cannot just cast a List<dynamic> to List<int> and so on.
-  static Map<RatchetMapKey, bool> enableCacheFromJson(
-    Map<String, dynamic> json,
-  ) {
-    return (json['enable']! as Map<String, dynamic>).map<RatchetMapKey, bool>(
-      (key, value) => MapEntry(
-        RatchetMapKey.fromJsonKey(key),
-        value as bool,
+    await commit(
+      BTBVTrustData(
+        jid,
+        deviceId,
+        trustCache[key]!,
+        enabled,
+        false,
       ),
     );
   }
 
   @override
   Future<void> removeTrustDecisionsForJid(String jid) async {
-    await _lock.synchronized(() async {
-      devices.remove(jid);
-      await commitState();
-    });
+    // 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);
   }
 
-  /// 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<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);
+    }
+  }
 
   @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 {}
-}

lib/src/trust/never.dart

@@ -22,5 +22,5 @@ class NeverTrustingTrustManager extends TrustManager {
   Future<void> removeTrustDecisionsForJid(String jid) async {}
 
   @override
-  Future<Map<String, dynamic>> toJson() async => <String, dynamic>{};
+  Future<void> loadTrustData(String jid) async {}
 }

lib/src/x3dh/x3dh.dart

@@ -1,15 +1,14 @@
 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);
@@ -70,7 +69,8 @@ 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(
+Future<Result<InvalidKeyExchangeSignatureError, X3DHAliceResult>>
+    x3dhFromBundle(
   OmemoBundle bundle,
   OmemoKeyPair ik,
 ) async {
@@ -84,7 +84,7 @@ Future<X3DHAliceResult> x3dhFromBundle(
   );
 
   if (!signatureValue) {
-    throw InvalidSignatureException();
+    return Result(InvalidKeyExchangeSignatureError());
   }
 
   // Generate EK
@@ -106,7 +106,7 @@ Future<X3DHAliceResult> x3dhFromBundle(
     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

pubspec.yaml

@@ -1,6 +1,6 @@
 name: omemo_dart
 description: An XMPP library independent OMEMO library
-version: 0.4.3
+version: 0.5.0
 homepage: https://github.com/PapaTutuWawa/omemo_dart
 publish_to: https://git.polynom.me/api/packages/PapaTutuWawa/pub
 
@@ -13,12 +13,15 @@ dependencies:
   hex: ^0.2.0
   logging: ^1.0.2
   meta: ^1.7.0
+  moxlib:
+    version: ^0.2.0
+    hosted: https://git.polynom.me/api/packages/Moxxy/pub
   pinenacl: ^0.5.1
+  protobuf: ^2.1.0
+  protoc_plugin: ^20.0.1
   synchronized: ^3.0.0+2
 
 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

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';
@@ -57,7 +28,8 @@ void main() {
     );
 
     // 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
     // ...
@@ -74,23 +46,28 @@ 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,
-      0,
+      resultAlice.opkId,
     );
     final bobsRatchet = await OmemoDoubleRatchet.acceptNewSession(
       spkBob,
+      bundleBob.spkId,
       ikAlice.pk,
+      2,
+      resultAlice.ek.pk,
       resultBob.sk,
       resultBob.ad,
-      0,
     );
 
     expect(alicesRatchet.sessionAd, bobsRatchet.sessionAd);
@@ -98,40 +75,42 @@ 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');
+        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');
+        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

@@ -1,186 +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],
-      );
-    });
-
-    test('Test some special cases', () {
-      expect(decodeVarint(encodeVarint(1042464893), 0).n, 1042464893);
-    });
-  });
-
-  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('Test decoding an issue', () {
-      /*
-      final data = 'CAAQfRogc2GwslU219dUkrMHNM4KdZRmuFnBTae+bQaJ+55IsAMiII7aZKj2sUpb6xR/3Ari7WZUmKFV0G6czUc4NMvjKDBaKnwKEM2ZpI8X3TgcxhxwENANnlsSaAgAEAAaICy8T9WPgLb7RdYd8/4JkrLF0RahEkC3ZaEfk5jw3dsLIkBMILzLyByweLgF4lCn0oNea+kbdrFr6rY7r/7WyI8hXEQz38QpnN+jyGGwC7Ga0dq70WuyqE7VpiFArQwqZh2G';
-      final kex = OmemoKeyExchange.fromBuffer(base64Decode(data));
-
-      expect(kex.spkId!, 1042464893);
-      */
-    });
-  });
-}

test/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

@@ -1,155 +0,0 @@
-import 'dart:convert';
-import 'package:omemo_dart/omemo_dart.dart';
-import 'package:omemo_dart/src/trust/always.dart';
-import 'package:test/test.dart';
-
-Map<String, dynamic> jsonify(Map<String, dynamic> map) {
-  return jsonDecode(jsonEncode(map)) as Map<String, dynamic>;
-}
-
-void main() {
-  test('Test serialising and deserialising the Device', () async {
-    // Generate a random session
-    final oldSession = await OmemoSessionManager.generateNewIdentity(
-      'user@test.server',
-      AlwaysTrustingTrustManager(),
-      opkAmount: 1,
-    );
-    final oldDevice = await oldSession.getDevice();
-    final serialised = jsonify(await oldDevice.toJson());
-
-    final newDevice = OmemoDevice.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 = jsonify(await oldDevice.toJson());
-
-    final newDevice = OmemoDevice.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,
-      getTimestamp(),
-    );
-    final aliceOld =
-        aliceSession.getRatchet(bobJid, await bobSession.getDeviceId());
-    final aliceSerialised = jsonify(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 = jsonify(await oldSession.toJsonWithoutSessions());
-    final newSession = OmemoSessionManager.fromJsonWithoutSessions(
-      serialised,
-      // NOTE: At this point, we don't care about this attribute
-      {},
-      AlwaysTrustingTrustManager(),
-    );
-
-    final oldDevice = await oldSession.getDevice();
-    final newDevice = await newSession.getDevice();
-    expect(await oldDevice.equals(newDevice), true);
-    expect(await oldSession.getDeviceMap(), await newSession.getDeviceMap());
-  });
-
-  test('Test serializing and deserializing RatchetMapKey', () {
-    const test1 = RatchetMapKey('user@example.org', 1234);
-    final result1 = RatchetMapKey.fromJsonKey(test1.toJsonKey());
-    expect(result1.jid, test1.jid);
-    expect(result1.deviceId, test1.deviceId);
-
-    const test2 = RatchetMapKey('user@example.org/hallo:welt', 3333);
-    final result2 = RatchetMapKey.fromJsonKey(test2.toJsonKey());
-    expect(result2.jid, test2.jid);
-    expect(result2.deviceId, test2.deviceId);
-  });
-
-  test('Test serializing and deserializing the components of the BTBV manager',
-      () async {
-    // Caroline's BTBV manager
-    final btbv = MemoryBTBVTrustManager();
-    // Example data
-    const aliceJid = 'alice@some.server';
-    const bobJid = 'bob@other.server';
-
-    await btbv.onNewSession(aliceJid, 1);
-    await btbv.setDeviceTrust(aliceJid, 1, BTBVTrustState.verified);
-    await btbv.onNewSession(aliceJid, 2);
-    await btbv.onNewSession(bobJid, 3);
-    await btbv.onNewSession(bobJid, 4);
-
-    final serialized = jsonify(await btbv.toJson());
-    final deviceList =
-        BlindTrustBeforeVerificationTrustManager.deviceListFromJson(
-      serialized,
-    );
-    expect(btbv.devices, deviceList);
-
-    final trustCache =
-        BlindTrustBeforeVerificationTrustManager.trustCacheFromJson(
-      serialized,
-    );
-    expect(btbv.trustCache, trustCache);
-
-    final enableCache =
-        BlindTrustBeforeVerificationTrustManager.enableCacheFromJson(
-      serialized,
-    );
-    expect(btbv.enablementCache, enableCache);
-  });
-}

test/trust_test.dart

@@ -4,7 +4,7 @@ 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';

test/x3dh_test.dart

@@ -26,7 +26,8 @@ void main() {
     );
 
     // 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
     // ...
@@ -68,18 +69,7 @@ void main() {
     );
 
     // 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');
+    final result = await x3dhFromBundle(bundleBob, ikAlice);
+    expect(result.isType<InvalidKeyExchangeSignatureError>(), isTrue);
   });
 }