???: Move code around

lib/omemo_dart.dart

@@ -1,6 +1,8 @@
 library omemo_dart;
 
 export 'src/bundle.dart';
+export 'src/double_ratchet.dart';
 export 'src/errors.dart';
+export 'src/helpers.dart';
 export 'src/key.dart';
 export 'src/x3dh.dart';

lib/src/double_ratchet.dart

@@ -1,281 +1,196 @@
-import 'dart:convert';
 import 'package:cryptography/cryptography.dart';
+import 'package:meta/meta.dart';
 import 'package:omemo_dart/protobuf/schema.pb.dart';
-import 'package:omemo_dart/src/bundle.dart';
+import 'package:omemo_dart/src/double_ratchet/crypto.dart';
+import 'package:omemo_dart/src/double_ratchet/kdf.dart';
 import 'package:omemo_dart/src/helpers.dart';
 import 'package:omemo_dart/src/key.dart';
 import 'package:omemo_dart/src/x3dh.dart';
 
-class OmemoRatchetStepResult {
+/// Amount of messages we may skip per session
+const maxSkip = 1000;
 
-  const OmemoRatchetStepResult(this.header, this.cipherText);
+class RatchetStep {
-  final List<int> header;
+
-  final List<int> cipherText;
+  const RatchetStep(this.header, this.ciphertext);
+  final OMEMOMessage header;
+  final List<int> ciphertext;
 }
 
-class OmemoEncryptionResult {
+@immutable
+class SkippedKey {
 
-  const OmemoEncryptionResult(this.cipherText, this.keys);
+  const SkippedKey(this.dh, this.n);
-  /// The encrypted plaintext
+  final OmemoPublicKey dh;
-  final List<int> cipherText;
+  final int n;
-  /// Mapping between Device id and the key to decrypt cipherText;
+
-  final Map<String, List<int>> keys;
+  @override
+  bool operator ==(Object other) {
+    return other is SkippedKey && other.dh == dh && other.n == n;
   }
 
-/// The session state of one party
+  @override
-class AliceOmemoSession {
+  int get hashCode => dh.hashCode ^ n.hashCode;
+}
 
-  AliceOmemoSession(
+class OmemoDoubleRatchet {
-    this.dhs,
+
-    this.dhr,
+  OmemoDoubleRatchet(
-    this.ek,
+    this.dhs, // DHs
-    this.rk,
+    this.dhr, // DHr
-    this.cks,
+    this.rk,  // RK
-    this.ckr,
+    this.cks, // CKs
-    this.ns,
+    this.ckr, // CKr
-    this.nr,
+    this.ns,  // Ns
-    this.pn,
+    this.nr,  // Nr
-    // this.skippedMessages,
+    this.pn,  // Pn
-    this.ad,
+    this.sessionAd,
   );
      
-  /// The Diffie-Hellman sending key pair
+  /// Sending DH keypair
-  final OmemoKeyPair dhs;
+  OmemoKeyPair dhs;
 
-  /// The Diffie-Hellman receiving key pair
+  /// Receiving Public key
-  final OmemoPublicKey dhr;
+  OmemoPublicKey? dhr;
 
-  /// The EK used by X3DH
+  /// 32 byte Root Key
-  final OmemoKeyPair ek;
-  
-  /// The Root Key
   List<int> rk;
 
-  /// Sending Chain Key
+  /// Sending and receiving Chain Keys
-  List<int> cks;
+  List<int>? cks;
-
-  /// Receiving Chain Key
   List<int>? ckr;
 
-  /// Message number for sending
+  /// Sending and receiving message numbers
   int ns;
-
-  /// Message number for receiving
   int nr;
 
-  /// Number of messages in the previous sending chain
+  /// Previous sending chain number
   int pn;
 
-  /// The associated data from the X3DH
+  final List<int> sessionAd;
-  final List<int> ad;
 
-  // TODO(PapaTutuWawa): Track skipped over message keys
+  final Map<SkippedKey, List<int>> mkSkipped = {};
 
-  static Future<AliceOmemoSession> newSession(OmemoBundle bundle, OmemoKeyPair ik) async {
+  /// This is performed by the initiating entity
-    // TODO(PapaTutuWawa): Error handling
+  static Future<OmemoDoubleRatchet> initiateNewSession(OmemoPublicKey spk, List<int> sk, List<int> ad) async {
-    final x3dhResult = await x3dhFromBundle(bundle, ik);
     final dhs = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
-    final dhr = bundle.ik;
+    final dhr = spk;
-    final ek = x3dhResult.ek;
+    final rk  = await kdfRk(sk, await dh(dhs, dhr, 0));
-    final sk = x3dhResult.sk;
+    final cks = rk;
-    final kdfRkResult = await kdfRk(sk, await dh(dhs, dhr, 2));
 
-    return AliceOmemoSession(
+    return OmemoDoubleRatchet(
       dhs,
       dhr,
-      ek,
+      rk,
-      kdfRkResult.rk,
+      cks,
-      kdfRkResult.ck,
       null,
       0,
       0,
       0,
-      x3dhResult.ad,
+      ad,
     );
   }
 
-  /// The associated_data parameter is implicit as it belongs to the session
+  /// This is performed by the accepting entity
-  Future<List<int>> _encrypt(List<int> mk, List<int> plaintext, List<int> associatedData) async {
+  static Future<OmemoDoubleRatchet> acceptNewSession(OmemoKeyPair spk, List<int> sk, List<int> ad) async {
-    final algorithm = Hkdf(
+    final dhs = spk;
-      hmac: Hmac(Sha256()),
+    return OmemoDoubleRatchet(
-      outputLength: 80,
+      dhs,
+      null,
+      sk,
+      null,
+      null,
+      0,
+      0,
+      0,
+      ad,
     );
-    final hkdfResult = await algorithm.deriveKey(
-      secretKey: SecretKey(mk),
-      nonce: List<int>.filled(32, 0x00),
-      info: utf8.encode(encryptHkdfInfoString),
-    );
-    final bytes = await hkdfResult.extractBytes();
-
-    final encKey = bytes.sublist(0, 32);
-    final authKey = bytes.sublist(32, 64);
-    final iv = bytes.sublist(64, 82);
-
-    // TODO(PapaTutuWawa): Remove once done
-    assert(encKey.length == 32);
-    assert(authKey.length == 32);
-    assert(iv.length == 16);
-
-    // 32 = 256 / 8
-    final encodedPlaintext = pkcs7padding(plaintext, 32);
-
-    final aesAlgorithm = AesCbc.with256bits(
-      macAlgorithm: Hmac.sha256(),
-    );
-    final secretBox = await aesAlgorithm.encrypt(
-      encodedPlaintext,
-      secretKey: SecretKey(encKey),
-      nonce: iv,
-    );
-
-    final ad_ = associatedData.sublist(0, ad.length);
-    final message = OMEMOMessage.fromBuffer(associatedData.sublist(ad.length))
-      ..ciphertext = secretBox.cipherText;
-    final messageBytes = message.writeToBuffer();
-
-    final input = concat([ad_, messageBytes]);
-    final authBytes = (await Hmac.sha256().calculateMac(
-      input,
-      secretKey: SecretKey(authKey),
-    )).bytes.sublist(0, 16);
-
-    final authenticatedMessage = OMEMOAuthenticatedMessage()
-      ..mac = authBytes
-      ..message = messageBytes;
-
-    return authenticatedMessage.writeToBuffer();
   }
   
-  Future<List<int>> ratchetStep(List<int> plaintext) async {
+  Future<RatchetStep> ratchetEncrypt(List<int> plaintext) async {
-    final kdfResult = await kdfCk(cks);
+    final newCks = await kdfCk(cks!, kdfCkNextChainKey);
-    final message = OMEMOMessage()
+    final mk = await kdfCk(cks!, kdfCkNextMessageKey);
-      ..dhPub = await dhs.pk.getBytes()
+
+    cks = newCks;
+    final header = OMEMOMessage()
+      ..n = ns
       ..pn = pn
-      ..n = ns;
+      ..dhPub = await dhs.pk.getBytes();
-    final header = message.writeToBuffer();
 
-    cks = kdfResult.ck;
     ns++;
 
-    return _encrypt(
+    return RatchetStep(
-      kdfResult.mk,
+      header,
-      plaintext,
+      await encrypt(mk, plaintext, concat([sessionAd, header.writeToBuffer()]), sessionAd),
-      concat([ad, header]),
-    );
-  }
-}
-
-Future<OmemoEncryptionResult> encryptForSessions(List<AliceOmemoSession> sessions, String plaintext) async {
-  // TODO(PapaTutuWawa): Generate random data
-  final key = List<int>.filled(32, 0x0);
-  final algorithm = Hkdf(
-    hmac: Hmac(Sha256()),
-    outputLength: 80,
-  );
-  final result = await algorithm.deriveKey(
-    secretKey: SecretKey(key),
-    nonce: List<int>.filled(32, 0x0),
-    info: utf8.encode(encryptionHkdfInfoString),
-  );
-  final bytes = await result.extractBytes();
-
-  final encKey = bytes.sublist(0, 32);
-  final authKey = bytes.sublist(32, 64);
-  final iv = bytes.sublist(64, 80);
-
-  final encodedPlaintext = pkcs7padding(utf8.encode(plaintext), 32);
-  final aesAlgorithm = AesCbc.with256bits(
-    macAlgorithm: Hmac.sha256(),
-  );
-  final secretBox = await aesAlgorithm.encrypt(
-    encodedPlaintext,
-    secretKey: SecretKey(encKey),
-    nonce: iv,
-  );
-  final hmac = (await Hmac.sha256().calculateMac(
-    secretBox.cipherText,
-    secretKey: SecretKey(authKey),
-  )).bytes.sublist(0, 16);
-
-  final keyData = concat([encKey, hmac]);
-
-  final keyMap = <String, List<int>>{};
-  for (final session in sessions) {
-    final ratchetKey = await session.ratchetStep(keyData);
-  }
-  
-  return OmemoEncryptionResult(
-    secretBox.cipherText,
-    keyMap,
     );
   }
 
-/// Result of the KDF_RK function from the Double Ratchet spec.
+  Future<List<int>?> trySkippedMessageKeys(OMEMOMessage header, List<int> ciphertext) async {
-class KdfRkResult {
+    final key = SkippedKey(
+      // TODO(PapaTutuWawa): Is this correct
+      OmemoPublicKey.fromBytes(header.dhPub, KeyPairType.ed25519),
+      header.n,
+    );
+    if (mkSkipped.containsKey(key)) {
+      final mk = mkSkipped[key]!;
+      mkSkipped.remove(key);
 
-  const KdfRkResult(this.rk, this.ck);
+      return decrypt(mk, ciphertext, concat([sessionAd, header.writeToBuffer()]), sessionAd);
-  /// 32 byte Root Key
-  final List<int> rk;
-
-  /// 32 byte Chain Key
-  final List<int> ck;
     }
 
-/// Result of the KDF_CK function from the Double Ratchet spec.
+    return null;
-class KdfCkResult {
-
-  const KdfCkResult(this.ck, this.mk);
-  /// 32 byte Chain Key
-  final List<int> ck;
-
-  /// 32 byte Message Key
-  final List<int> mk;
   }
 
-/// Amount of messages we may skip per session
+  Future<void> skipMessageKeys(int until) async {
-const maxSkip = 1000;
+    if (nr + maxSkip < until) {
-
+      // TODO(PapaTutuWawa): Custom exception
-/// Info string for KDF_RK
+      throw Exception();
-const kdfRkInfoString = 'OMEMO Root Chain';
-
-/// Info string for ENCRYPT
-const encryptHkdfInfoString = 'OMEMO Message Key Material';
-
-/// Info string for encrypting a message
-const encryptionHkdfInfoString = 'OMEMO Payload';
-
-/// Flags for KDF_CK
-const kdfCkNextMessageKey = 0x01;
-const kdfCkNextChainKey = 0x02;
-
-Future<KdfRkResult> kdfRk(List<int> rk, List<int> dhOut) async {
-  final algorithm = Hkdf(
-    hmac: Hmac(Sha256()),
-    outputLength: 32,
-  );
-  final result = await algorithm.deriveKey(
-    secretKey: SecretKey(dhOut),
-    nonce: rk,
-    info: utf8.encode(kdfRkInfoString),
-  );
-
-  // TODO(PapaTutuWawa): Does the rk in the tuple (rk, ck) refer to the input rk?
-  return KdfRkResult(rk, await result.extractBytes());
     }
 
-Future<KdfCkResult> kdfCk(List<int> ck) async {
+    if (ckr != null) {
-  final hkdf = Hkdf(hmac: Hmac(Sha256()), outputLength: 32);
+      while (nr < until) {
-  final newCk = await hkdf.deriveKey(
+        final newCkr = await kdfCk(ckr!, kdfCkNextChainKey);
-    secretKey: SecretKey(ck),
+        final mk = await kdfCk(ckr!, kdfCkNextMessageKey);
-    nonce: [kdfCkNextChainKey],
+        ckr = newCkr;
-  );
+        mkSkipped[SkippedKey(dhr!, nr)] = mk;
-  final mk = await hkdf.deriveKey(
+        nr++;
-    secretKey: SecretKey(ck),
+      }
-    nonce: [kdfCkNextMessageKey],
+    }
-  );
+  }
-
+
-  return KdfCkResult(
+  Future<void> dhRatchet(OMEMOMessage header) async {
-    await newCk.extractBytes(),
+    pn = header.n;
-    await mk.extractBytes(),
+    ns = 0;
-  );
+    nr = 0;
+    dhr = OmemoPublicKey.fromBytes(header.dhPub, KeyPairType.ed25519);
+
+    final newRk = await kdfRk(rk, await dh(dhs, dhr!, 2));
+    rk = newRk;
+    ckr = newRk;
+    dhs = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
+    final newNewRk = await kdfRk(rk, await dh(dhs, dhr!, 2));
+    rk = newNewRk;
+    cks = newNewRk;
+  }
+  
+  Future<List<int>> ratchetDecrypt(OMEMOMessage header, List<int> ciphertext) async {
+    // Check if we skipped too many messages
+    final plaintext = await trySkippedMessageKeys(header, ciphertext);
+    if (plaintext != null) {
+      return plaintext;
+    }
+
+    if (header.dhPub != await dhr?.getBytes()) {
+      await skipMessageKeys(header.pn);
+      await dhRatchet(header);
+    }
+
+    await skipMessageKeys(header.n);
+    final newCkr = await kdfCk(ckr!, kdfCkNextChainKey);
+    final mk = await kdfCk(ckr!, kdfCkNextMessageKey);
+    ckr = newCkr;
+    nr++;
+
+    return decrypt(mk, ciphertext, concat([sessionAd, header.writeToBuffer()]), sessionAd);
+  }
 }

lib/src/double_ratchet/crypto.dart

@@ -0,0 +1,109 @@
+import 'dart:convert';
+import 'package:cryptography/cryptography.dart';
+import 'package:omemo_dart/protobuf/schema.pb.dart';
+import 'package:omemo_dart/src/helpers.dart';
+
+/// Info string for ENCRYPT
+const encryptHkdfInfoString = 'OMEMO Message Key Material';
+
+/// cryptography _really_ wants to check the MAC output from AES-256-CBC. Since
+/// we don't have it, we need the MAC check to always "pass".
+class NoMacSecretBox extends SecretBox {
+  NoMacSecretBox(super.cipherText, { required super.nonce }) : super(mac: Mac.empty);
+
+  @override
+  Future<void> checkMac({
+    required MacAlgorithm macAlgorithm,
+    required SecretKey secretKey,
+    required List<int> aad,
+  }) async {}
+}
+
+/// Signals ENCRYPT function as specified by OMEMO 0.8.0.
+/// 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 {
+  final hkdf = Hkdf(
+    hmac: Hmac(Sha256()),
+    outputLength: 80,
+  );
+  final hkdfResult = await hkdf.deriveKey(
+    secretKey: SecretKey(mk),
+    nonce: List<int>.filled(32, 0x0),
+    info: utf8.encode(encryptHkdfInfoString),
+  );
+  final hkdfBytes = await hkdfResult.extractBytes();
+
+  // Split hkdfBytes into encryption, authentication key and IV
+  final encryptionKey = hkdfBytes.sublist(0, 32);
+  final authenticationKey = hkdfBytes.sublist(32, 64);
+  final iv = hkdfBytes.sublist(64, 80);
+
+  final aesResult = await AesCbc.with256bits(
+    macAlgorithm: MacAlgorithm.empty,
+  ).encrypt(
+    plaintext,
+    secretKey: SecretKey(encryptionKey),
+    nonce: iv,
+  );
+  
+  final header = OMEMOMessage.fromBuffer(associatedData.sublist(sessionAd.length))
+    ..ciphertext = aesResult.cipherText;
+  final headerBytes = header.writeToBuffer();
+  final hmacInput = concat([sessionAd, headerBytes]);
+  final hmacResult = (await Hmac.sha256().calculateMac(
+    hmacInput,
+    secretKey: SecretKey(authenticationKey),
+  )).bytes.sublist(0, 16);
+  
+  final message = OMEMOAuthenticatedMessage()
+    ..mac = hmacResult
+    ..message = headerBytes;
+  return message.writeToBuffer();
+}
+
+/// Signals DECRYPT function as specified by OMEMO 0.8.0.
+/// 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 the keys and iv from mk
+  final hkdf = Hkdf(
+    hmac: Hmac(Sha256()),
+    outputLength: 80,
+  );
+  final hkdfResult = await hkdf.deriveKey(
+    secretKey: SecretKey(mk),
+    nonce: List<int>.filled(32, 0x0),
+    info: utf8.encode(encryptHkdfInfoString),
+  );
+  final hkdfBytes = await hkdfResult.extractBytes();
+
+  // Split hkdfBytes into encryption, authentication key and IV
+  final encryptionKey = hkdfBytes.sublist(0, 32);
+  final authenticationKey = hkdfBytes.sublist(32, 64);
+  final iv = hkdfBytes.sublist(64, 80);
+  
+  // 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 Hmac.sha256().calculateMac(
+    hmacInput,
+    secretKey: SecretKey(authenticationKey),
+  )).bytes.sublist(0, 16);
+
+  // TODO(PapaTutuWawa): Check the HMAC result
+  
+  final plaintext = await AesCbc.with256bits(
+    macAlgorithm: MacAlgorithm.empty,
+  ).decrypt(
+    NoMacSecretBox(
+      header.ciphertext,
+      nonce: iv,
+    ),
+    secretKey: SecretKey(encryptionKey),
+  );
+
+  return plaintext;
+}

lib/src/double_ratchet/kdf.dart

@@ -0,0 +1,35 @@
+import 'dart:convert';
+import 'package:cryptography/cryptography.dart';
+
+/// Info string for KDF_RK
+const kdfRkInfoString = 'OMEMO Root Chain';
+
+/// Flags for KDF_CK
+const kdfCkNextMessageKey = 0x01;
+const kdfCkNextChainKey = 0x02;
+
+/// Signals KDF_CK function as specified by OMEMO 0.8.0.
+Future<List<int>> kdfCk(List<int> ck, int constant) async {
+  final hkdf = Hkdf(hmac: Hmac(Sha256()), outputLength: 32);
+  final result = await hkdf.deriveKey(
+    secretKey: SecretKey(ck),
+    nonce: [constant],
+  );
+
+  return result.extractBytes();
+}
+
+/// Signals KDF_RK function as specified by OMEMO 0.8.0.
+Future<List<int>> kdfRk(List<int> rk, List<int> dhOut) async {
+  final algorithm = Hkdf(
+    hmac: Hmac(Sha256()),
+    outputLength: 32,
+  );
+  final result = await algorithm.deriveKey(
+    secretKey: SecretKey(dhOut),
+    nonce: rk,
+    info: utf8.encode(kdfRkInfoString),
+  );
+
+  return result.extractBytes();
+}

lib/src/x3dh.dart

@@ -59,6 +59,9 @@ Future<List<int>> dh(OmemoKeyPair kp, OmemoPublicKey pk, int identityKey) async
     ckp = await kp.toCurve25519();
   } else if (identityKey == 2) {
     cpk = await pk.toCurve25519();
+  } else if (identityKey == 3) {
+    ckp = await kp.toCurve25519();
+    cpk = await pk.toCurve25519();
   }
 
   final shared = await Cryptography.instance.x25519().sharedSecretKey(

test/double_ratchet_test.dart

@@ -0,0 +1,109 @@
+import 'dart:convert';
+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
+    final ikAlice = await OmemoKeyPair.generateNewPair(KeyPairType.ed25519);
+    final ikBob = await OmemoKeyPair.generateNewPair(KeyPairType.ed25519);
+    final spkBob = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
+    final opkBob = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
+    final bundleBob = OmemoBundle(
+      '1',
+      await spkBob.pk.asBase64(),
+      '3',
+      base64Encode(
+        await sig(ikBob, await spkBob.pk.getBytes()),
+      ),
+      //'Q5in+/L4kJixEX692h6mJkPMyp4I3SlQ84L0E7ipPzqfPHOMiraUlqG2vG/O8wvFjLsKYZpPBraga9IvwhqVDA==',
+      await ikBob.pk.asBase64(),
+      {
+        '2': await opkBob.pk.asBase64(),
+      },
+    );
+    
+    // Alice does X3DH
+    final resultAlice = await x3dhFromBundle(bundleBob, ikAlice);
+
+    // Alice sends the inital message to Bob
+    // ...
+    
+    // Bob does X3DH
+    final resultBob = await x3dhFromInitialMessage(
+      X3DHMessage(
+        ikAlice.pk,
+        resultAlice.ek.pk,
+        '2',
+      ),
+      spkBob,
+      opkBob,
+      ikBob,
+    );
+
+    print('X3DH key exchange done');
+
+    // Alice and Bob now share sk as a common secret and ad
+    final alicesRatchet = await OmemoDoubleRatchet.initiateNewSession(
+      spkBob.pk,
+      resultAlice.sk,
+      resultAlice.ad,
+    );
+    final bobsRatchet = await OmemoDoubleRatchet.acceptNewSession(
+      spkBob,
+      resultBob.sk,
+      resultBob.ad,
+    );
+
+    expect(alicesRatchet.sessionAd, bobsRatchet.sessionAd);
+    //expect(await alicesRatchet.dhr.getBytes(), await ikBob.pk.getBytes());
+    
+    // Alice encrypts a message
+    final aliceRatchetResult = await alicesRatchet.ratchetEncrypt(utf8.encode('Hello Bob'));
+    print('Alice sent the message');
+
+    // Alice sends it to Bob
+    // ...
+
+    // Bob tries to decrypt it
+    final bobRatchetResult = await bobsRatchet.ratchetDecrypt(
+      aliceRatchetResult.header,
+      aliceRatchetResult.ciphertext,
+    );
+    print('Bob decrypted the message');
+
+    expect(utf8.encode('Hello Bob'), bobRatchetResult);
+  });
+  */
+}