diff --git a/lib/core/backup_service.dart b/lib/core/backup_service.dart
index 850e9560d..9b2b2c7d4 100644
--- a/lib/core/backup_service.dart
+++ b/lib/core/backup_service.dart
@@ -160,7 +160,7 @@ class BackupService {
     }
 
     final data =
-        json.decode(preferencesFile.readAsStringSync()) as Map<String, Object>;
+        json.decode(preferencesFile.readAsStringSync()) as Map<String, dynamic>;
     String currentWalletName = data[PreferencesKey.currentWalletName] as String;
     int currentWalletType = data[PreferencesKey.currentWalletType] as int;
 
@@ -173,43 +173,87 @@ class BackupService {
       currentWalletType = serializeToInt(_correctWallets.first.type);
     }
 
+    final currentNodeId = data[PreferencesKey.currentNodeIdKey] as int?;
+    final currentBalanceDisplayMode = data[PreferencesKey.currentBalanceDisplayModeKey] as int?;
+    final currentFiatCurrency = data[PreferencesKey.currentFiatCurrencyKey] as String?;
+    final shouldSaveRecipientAddress = data[PreferencesKey.shouldSaveRecipientAddressKey] as bool?;
+    final currentTransactionPriorityKeyLegacy = data[PreferencesKey.currentTransactionPriorityKeyLegacy] as int?;
+    final allowBiometricalAuthentication = data[PreferencesKey.allowBiometricalAuthenticationKey] as bool?;
+    final currentBitcoinElectrumSererId = data[PreferencesKey.currentBitcoinElectrumSererIdKey] as int?;
+    final currentLanguageCode = data[PreferencesKey.currentLanguageCode] as String?;
+    final displayActionListMode = data[PreferencesKey.displayActionListModeKey] as int?;
+    final currentPinLength = data[PreferencesKey.currentPinLength] as int?;
+    final currentTheme = data[PreferencesKey.currentTheme] as int?;
+    final currentDefaultSettingsMigrationVersion = data[PreferencesKey.currentDefaultSettingsMigrationVersion] as int?;
+    final moneroTransactionPriority = data[PreferencesKey.moneroTransactionPriority] as int?;
+    final bitcoinTransactionPriority = data[PreferencesKey.bitcoinTransactionPriority] as int?;
+
     await _sharedPreferences.setString(PreferencesKey.currentWalletName,
         currentWalletName);
-    await _sharedPreferences.setInt(PreferencesKey.currentNodeIdKey,
-        data[PreferencesKey.currentNodeIdKey] as int);
-    await _sharedPreferences.setInt(PreferencesKey.currentBalanceDisplayModeKey,
-        data[PreferencesKey.currentBalanceDisplayModeKey] as int);
+
+    if (currentNodeId != null)
+      await _sharedPreferences.setInt(PreferencesKey.currentNodeIdKey,
+        currentNodeId);
+
+    if (currentBalanceDisplayMode != null)
+      await _sharedPreferences.setInt(PreferencesKey.currentBalanceDisplayModeKey,
+        currentBalanceDisplayMode);
+
     await _sharedPreferences.setInt(PreferencesKey.currentWalletType,
         currentWalletType);
-    await _sharedPreferences.setString(PreferencesKey.currentFiatCurrencyKey,
-        data[PreferencesKey.currentFiatCurrencyKey] as String);
-    await _sharedPreferences.setBool(
+
+    if (currentFiatCurrency != null)
+      await _sharedPreferences.setString(PreferencesKey.currentFiatCurrencyKey,
+        currentFiatCurrency);
+
+    if (shouldSaveRecipientAddress != null)
+      await _sharedPreferences.setBool(
         PreferencesKey.shouldSaveRecipientAddressKey,
-        data[PreferencesKey.shouldSaveRecipientAddressKey] as bool);
-    await _sharedPreferences.setInt(
+        shouldSaveRecipientAddress);
+
+    if (currentTransactionPriorityKeyLegacy != null)
+      await _sharedPreferences.setInt(
         PreferencesKey.currentTransactionPriorityKeyLegacy,
-        data[PreferencesKey.currentTransactionPriorityKeyLegacy] as int);
-    await _sharedPreferences.setBool(
+        currentTransactionPriorityKeyLegacy);
+
+    if (allowBiometricalAuthentication != null)
+      await _sharedPreferences.setBool(
         PreferencesKey.allowBiometricalAuthenticationKey,
-        data[PreferencesKey.allowBiometricalAuthenticationKey] as bool);
-    await _sharedPreferences.setInt(
+        allowBiometricalAuthentication);
+
+    if (currentBitcoinElectrumSererId != null)
+      await _sharedPreferences.setInt(
         PreferencesKey.currentBitcoinElectrumSererIdKey,
-        data[PreferencesKey.currentBitcoinElectrumSererIdKey] as int);
-    await _sharedPreferences.setString(PreferencesKey.currentLanguageCode,
-        data[PreferencesKey.currentLanguageCode] as String);
-    await _sharedPreferences.setInt(PreferencesKey.displayActionListModeKey,
-        data[PreferencesKey.displayActionListModeKey] as int);
-    await _sharedPreferences.setInt(PreferencesKey.currentPinLength,
-        data[PreferencesKey.currentPinLength] as int);
-    await _sharedPreferences.setInt(
-        PreferencesKey.currentTheme, data[PreferencesKey.currentTheme] as int);
-    await _sharedPreferences.setInt(
+        currentBitcoinElectrumSererId);
+
+    if (currentLanguageCode != null)
+      await _sharedPreferences.setString(PreferencesKey.currentLanguageCode,
+        currentLanguageCode);
+
+    if (displayActionListMode != null)
+      await _sharedPreferences.setInt(PreferencesKey.displayActionListModeKey,
+        displayActionListMode);
+
+    if (currentPinLength != null)
+      await _sharedPreferences.setInt(PreferencesKey.currentPinLength,
+        currentPinLength);
+
+    if (currentTheme != null)
+      await _sharedPreferences.setInt(
+        PreferencesKey.currentTheme, currentTheme);
+
+    if (currentDefaultSettingsMigrationVersion != null)
+      await _sharedPreferences.setInt(
         PreferencesKey.currentDefaultSettingsMigrationVersion,
-        data[PreferencesKey.currentDefaultSettingsMigrationVersion] as int);
-    await _sharedPreferences.setInt(PreferencesKey.moneroTransactionPriority,
-        data[PreferencesKey.moneroTransactionPriority] as int);
-    await _sharedPreferences.setInt(PreferencesKey.bitcoinTransactionPriority,
-        data[PreferencesKey.bitcoinTransactionPriority] as int);
+        currentDefaultSettingsMigrationVersion);
+
+    if (moneroTransactionPriority != null)
+      await _sharedPreferences.setInt(PreferencesKey.moneroTransactionPriority,
+        moneroTransactionPriority);
+
+    if (bitcoinTransactionPriority != null)
+      await _sharedPreferences.setInt(PreferencesKey.bitcoinTransactionPriority,
+        bitcoinTransactionPriority);
 
     await preferencesFile.delete();
   }
@@ -283,7 +327,7 @@ class BackupService {
 
   Future<String> _exportPreferencesJSON() async {
     // FIX-ME: Force unwrap
-    final preferences = <String, Object>{
+    final preferences = <String, dynamic>{
       PreferencesKey.currentWalletName:
           _sharedPreferences.getString(PreferencesKey.currentWalletName)!,
       PreferencesKey.currentNodeIdKey:
@@ -340,18 +384,15 @@ class BackupService {
   }
 
   Future<Uint8List> _decrypt(
-      Uint8List data, String secretKeySource, String nonceBase64) async {
-     throw Exception('Unimplemented');
-    //final secretKeyHash = await sha256.hash(utf8.encode(secretKeySource));
-    //final secretKey = SecretKey(secretKeyHash.bytes);
-    //final nonce = Nonce(base64.decode(nonceBase64));
-    //return await _cipher.decrypt(data, secretKey: secretKey, nonce: nonce);
-
-    // final secretKeyHash = await Cryptography.instance.sha256().hash(utf8.encode(secretKeySource));
-    // final secretKey = SecretKey(secretKeyHash.bytes);
-    // final nonce = base64.decode(nonceBase64).toList();
-    // final box = SecretBox(data.toList(), nonce: nonce, mac: Mac);
-    // final plainData = await _cipher.decrypt(box, secretKey: secretKey);
-    // return Uint8List.fromList(plainData);
+      Uint8List data, String secretKeySource, String nonceBase64, {int macLength = 16}) async {
+    final secretKeyHash = await Cryptography.instance.sha256().hash(utf8.encode(secretKeySource));
+    final secretKey = SecretKey(secretKeyHash.bytes);
+    final nonce = base64.decode(nonceBase64).toList();
+    final box = SecretBox(
+      Uint8List.sublistView(data, 0, data.lengthInBytes - macLength).toList(),
+      nonce: nonce,
+      mac: Mac(Uint8List.sublistView(data, data.lengthInBytes - macLength)));
+    final plainData = await _cipher.decrypt(box, secretKey: secretKey);
+    return Uint8List.fromList(plainData);
   }
 }