How to Obfuscate Kotlin Code in Android Apps

Last updated April 7, 2024 by Appdome

Learn to Obfuscate App Logic in Android apps, in mobile CI/CD with a Data-Driven DevSecOps™ build system.

What is Kotlin?

Kotlin is a cross-platform programming language, which is designed to fully interoperate with Java. For several years Kotlin has been approved by Google as a preferred language for Android app developers.

Since 2017, Kotlin has been included in Android Studio as an alternative to the standard Java compiler.

Why does Kotlin Need its Own Obfuscation?

Kotlin code has a section called metadata, which is found on each class file produced by the Kotlin compiler. Kotlin metadata holds important information about Kotlin classes. This information is crucial for Kotlin reflection, namely: a set of language and library features that allow inspecting, loading, and interacting with classes, fields, and methods at runtime.

Kotlin metadata holds not only information retrieved from the code itself, such as methods and variables but also additional information. As a result, this section requires its own obfuscation as part of the Kotlin obfuscation. In addition, each Kotlin version has its own metadata version, which affects its obfuscation.

As part of Appdome’s Total Code Obfuscation, Kotlin obfuscation is enabled by default for Kotlin versions 1.3.72 and higher.

Prerequisites for Using Obfuscate App Logic:

To use Appdome’s mobile app security build system to Obfuscate App Logic , you’ll need:

Appdome account (create a free Appdome account here)
A license for Obfuscate App Logic
Mobile App (.apk or .aab for Android)
Signing Credentials (see Signing Secure Android apps and Signing Secure iOS apps)

Obfuscate App Logic on Android apps using Appdome

On Appdome, follow these simple steps to create self-defending Android Apps that Obfuscate App Logic without an SDK or gateway:

Upload the Mobile App to Appdome.
1. Upload an app to Appdome’s Mobile App Security Build System
2. Upload Method: Appdome Console or DEV-API
3. Android Formats: .apk or .aab
4. Obfuscate App Logic Compatible With: Java, JS, C++, C#, Kotlin, Flutter, React Native, Unity, Xamarin, Cordova and other Android apps
Build the feature: Obfuscate App Logic.
1. Building Obfuscate App Logic by using Appdome’s DEV-API:
  1. Create and name the Fusion Set (security template) that will contain the Obfuscate App Logic feature as shown below:
  2. Follow the steps in Sections 2.2.1-2.2.2 of this article, Building the Obfuscate App Logic feature via Appdome Console, to add the Obfuscate App Logic feature to this Fusion Set.
  3. Open the Fusion Set Detail Summary by clicking the “...” symbol on the far-right corner of the Fusion Set. Copy the Fusion Set ID from the Fusion Set Detail Summary (as shown below):
    
    Figure 2: Fusion Set Detail Summary
    Note: Annotating the Fusion Set to identify the protection(s) selected is optional only (not mandatory).
  4. Follow the instructions below to use the Fusion Set ID inside any standard mobile DevOps or CI/CD toolkit like Bitrise, App Center, Jenkins, Travis, Team City, Circle CI or other system:
    
    Build an API for the app – for instructions, see the tasks under Appdome API Reference Guide
    
    Look for sample APIs in Appdome’s GitHub Repository
2. Building the Obfuscate App Logic feature via Appdome Console
  
  To build the Obfuscate App Logic protection by using Appdome Console, follow the instructions below.
  1. Where: Inside the Appdome Console, go to Build > Security Tab > TOTALCode™ Obfuscation section.
    Like all other options in ONEShield™, Obfuscate App Logic is turned on by default, as shown below:
    Figure 3: Obfuscate App Logic option
    Note: The App Compromise Notification contains an easy to follow default remediation path for the mobile app end user. You can customize this message as required to achieve brand specific support, workflow or other messaging.
  2. When you enable Obfuscate App Logic you'll notice that your Fusion Set you created in step 2.1.1 now bears the icon of the protection category that contains Obfuscate App Logic
    
    Figure 4: Fusion Set that displays the newly added Obfuscate App Logic protection
  3. Click Build My App at the bottom of the Build Workflow (shown in Figure 3).
Congratulations! The Obfuscate App Logic protection is now added to the mobile app
Certify the Obfuscate App Logic feature in Android Apps

After building Obfuscate App Logic, Appdome generates a Certified Secure™ certificate to guarantee that the Obfuscate App Logic protection has been added and is protecting the app. To verify that the Obfuscate App Logic protection has been added to the mobile app, locate the protection in the Certified Secure™ certificate as shown below:

Figure 5: Certified Secure™ certificate

Each Certified Secure™ certificate provides DevOps and DevSecOps organizations the entire workflow summary, audit trail of each build, and proof of protection that Obfuscate App Logic has been added to each Android app. Certified Secure provides instant and in-line DevSecOps compliance certification that Obfuscate App Logic and other mobile app security features are in each build of the mobile app

Using Threat-Events™ for App Logic Intelligence and Control in Android Apps

Appdome Threat-Events™ provides consumable in-app mobile app attack intelligence and defense control when App Logic is detected. To consume and use Threat-Events™ for App Logic in Android Apps, use registerReceiver in the Application OnCreate, and the code samples for Threat-Events™ for App Logic shown below.

The specifications and options for Threat-Events™ for App Logic are:

Threat-Event™ Elements	Obfuscate App Logic Method Detail
Appdome Feature Name	Obfuscate App Logic
Threat-Event Mode
OFF, IN-APP DEFENSE	Appdome detects, defends and notifies user (standard OS dialog) using customizable messaging.
ON, IN-APP DETECTION	Appdome detects the attack or threat and passes the event in a standard format to the app for processing (app chooses how and when to enforce).
ON, IN-APP DEFENSE	Uses Appdome Enforce mode for any attack or threat and passes the event in a standard format to the app for processing (gather intel on attacks and threats without losing any protection).
Certified Secure™ Threat Event Check	x
Visible in ThreatScope™	x
Developer Parameters for Obfuscating App Logic Threat-Event™
Threat-Event NAME
Threat-Event DATA	reasonData
Threat-Event CODE	reasonCode
Threat-Event REF
Threat-Event SCORE
currentThreatEventScore	Current Threat-Event score
threatEventsScore	Total Threat-events score

Threat-Event Context Keys
message	Message displayed for the user on event
failSafeEnforce	Timed enforcement against the identified threat
externalID	The external ID of the event which can be listened via Threat Events
osVersion	OS version of the current device
deviceModel	Current device model
deviceManufacturer	The manufacturer of the current device
fusedAppToken	The task ID of the Appdome fusion of the currently running app
kernelInfo	Info about the kernel: system name, node name, release, version and machine.
carrierPlmn	PLMN of the device. Only available for Android devices.
deviceID	Current device ID
reasonCode	Reason code of the occurred event
buildDate	Appdome fusion date of the current application
devicePlatform	OS name of the current device
carrierName	Carrier name of the current device. Only available for Android.
updatedOSVersion	Is the OS version up to date
deviceBrand	Brand of the device
deviceBoard	Board of the device
buildUser	Build user
buildHost	Build host
sdkVersion	Sdk version
timeZone	Time zone
deviceFaceDown	Is the device face down
locationLong	Location longitude conditioned by location permission
locationLat	Location latitude conditioned by location permission
locationState	Location state conditioned by location permission
wifiSsid	Wifi SSID
wifiSsidPermissionStatus	Wifi SSID permission status

With Threat-Events™ enabled (turned ON), Android developers can get detailed attack intelligence and granular defense control in Android applications and create amazing user experiences for all mobile end users when App Logic is detected.

The following is a code sample for native Android apps, which uses all values in the specification above for Obfuscate App Logic:

Important! Replace all placeholder instances of <Context Key> with the specific name of your threat event context key across all language examples. This is crucial to ensure your code functions correctly with the intended event data. For example, The <Context Key> could be the message, externalID, OS Version, reason code, etc.

                    IntentFilter intentFilter = new IntentFilter();
                    intentFilter.addAction("");
                    BroadcastReceiver threatEventReceiver = new BroadcastReceiver() {
                        @Override
                        public void onReceive(Context context, Intent intent) {
                            String message = intent.getStringExtra("message"); // Message shown to the user
                            String reasonData = intent.getStringExtra("reasonData"); // Threat detection cause
                            String reasonCode = intent.getStringExtra("reasonCode"); // Event reason code
                            
                            // Current threat event score
                            String currentThreatEventScore = intent.getStringExtra("currentThreatEventScore");
                            
                            // Total threat events score
                            String threatEventsScore = intent.getStringExtra("threatEventsScore");
                            
                            // Replace '' with your specific event context key
                            // String variable = intent.getStringExtra("");

                            // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
                        }
                    };

                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
                        registerReceiver(threatEventReceiver, intentFilter, Context.RECEIVER_NOT_EXPORTED);
                    } else {
                        registerReceiver(threatEventReceiver, intentFilter);
                    }

xxxxxxxxxx
 
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction("");
BroadcastReceiver threatEventReceiver = new BroadcastReceiver() {
  @Override
  public void onReceive(Context context, Intent intent) {
    String message = intent.getStringExtra("message"); // Message shown to the user
    String reasonData = intent.getStringExtra("reasonData"); // Threat detection cause
    String reasonCode = intent.getStringExtra("reasonCode"); // Event reason code
​
    // Current threat event score
    String currentThreatEventScore = intent.getStringExtra("currentThreatEventScore");
​
    // Total threat events score
    String threatEventsScore = intent.getStringExtra("threatEventsScore");
​
    // Replace '<Context Key>' with your specific event context key
    // String variable = intent.getStringExtra("<Context Key>");
​
    // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
  }
};
​
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
  registerReceiver(threatEventReceiver, intentFilter, Context.RECEIVER_NOT_EXPORTED);
} else {
  registerReceiver(threatEventReceiver, intentFilter);
}

                    val intentFilter = IntentFilter()
                    intentFilter.addAction("")
                    val threatEventReceiver = object : BroadcastReceiver() {
                        override fun onReceive(context: Context?, intent: Intent?) {
                            var message = intent?.getStringExtra("message") // Message shown to the user
                            var reasonData = intent?.getStringExtra("reasonData") // Threat detection cause
                            var reasonCode = intent?.getStringExtra("reasonCode") // Event reason code
                            
                            // Current threat event score
                            var currentThreatEventScore = intent?.getStringExtra("currentThreatEventScore")
                            
                            // Total threat events score
                            var threatEventsScore = intent?.getStringExtra("threatEventsScore")
                            
                            // Replace '' with your specific event context key
                            // var variable = intent?.getStringExtra("")

                            // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
                        }
                    }

                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
                        registerReceiver(threatEventReceiver, intentFilter, Context.RECEIVER_NOT_EXPORTED)
                    } else {
                        registerReceiver(threatEventReceiver, intentFilter)
                    }

xxxxxxxxxx
 
val intentFilter = IntentFilter()
intentFilter.addAction("")
val threatEventReceiver = object : BroadcastReceiver() {
    override fun onReceive(context: Context?, intent: Intent?) {
        var message = intent?.getStringExtra("message") // Message shown to the user
        var reasonData = intent?.getStringExtra("reasonData") // Threat detection cause
        var reasonCode = intent?.getStringExtra("reasonCode") // Event reason code
          
        // Current threat event score
        var currentThreatEventScore = intent?.getStringExtra("currentThreatEventScore")
          
        // Total threat events score
        var threatEventsScore = intent?.getStringExtra("threatEventsScore")
          
        // Replace '<Context Key>' with your specific event context key
        // var variable = intent?.getStringExtra("<Context Key>")
​
        // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
    }
}
​
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
  registerReceiver(threatEventReceiver, intentFilter, Context.RECEIVER_NOT_EXPORTED)
} else {
  registerReceiver(threatEventReceiver, intentFilter)
}

                const { ADDevEvents } = NativeModules;
                const aDDevEvents = new NativeEventEmitter(ADDevEvents);

                function registerToDevEvent(action, callback) {
                    NativeModules.ADDevEvents.registerForDevEvent(action);
                    aDDevEvents.addListener(action, callback);
                }

                export function registerToAllEvents() {
                    registerToDevEvent(
                        "",
                        (userinfo) => Alert.alert(JSON.stringify(userinfo))

                        var message = userinfo["message"] // Message shown to the user
                        var reasonData = userinfo["reasonData"] // Threat detection cause
                        var reasonCode = userinfo["reasonCode"] // Event reason code

                        // Current threat event score
                        var currentThreatEventScore = userinfo["currentThreatEventScore"]

                        // Total threat events score
                        var threatEventsScore = userinfo["threatEventsScore"]

                        // Replace '' with your specific event context key
                        // var variable = userinfo[""]

                        // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
                    );
                }

xxxxxxxxxx
 
const { ADDevEvents } = NativeModules;
const aDDevEvents = new NativeEventEmitter(ADDevEvents);
​
function registerToDevEvent(action, callback) {
    NativeModules.ADDevEvents.registerForDevEvent(action);
    aDDevEvents.addListener(action, callback);
}
​
export function registerToAllEvents() {
    registerToDevEvent(
        "",
        (userinfo) => Alert.alert(JSON.stringify(userinfo))
​
        var message = userinfo["message"] // Message shown to the user
        var reasonData = userinfo["reasonData"] // Threat detection cause
        var reasonCode = userinfo["reasonCode"] // Event reason code
​
        // Current threat event score
        var currentThreatEventScore = userinfo["currentThreatEventScore"]
​
        // Total threat events score
        var threatEventsScore = userinfo["threatEventsScore"]
​
        // Replace '<Context Key>' with your specific event context key
        // var variable = userinfo["<Context Key>"]
​
        // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
    );
}

                RegisterReceiver(new ThreatEventReceiver(), new IntentFilter(""));
                
                class ThreatEventReceiver : BroadcastReceiver
                {
                    public override void OnReceive(Context context, Intent intent)
                    {
                        String message = intent.GetStringExtra("message"); // Message shown to the user
                        String reasonData = intent.GetStringExtra("reasonData"); // Threat detection cause
                        String reasonCode = intent.GetStringExtra("reasonCode"); // Event reason code

                        // Current threat event score
                        String currentThreatEventScore = intent.GetStringExtra("currentThreatEventScore");

                        // Total threat events score
                        String threatEventsScore = intent.GetStringExtra("threatEventsScore");

                        // Replace '' with your specific event context key
                        // String variable = intent.GetStringExtra("");

                        // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
                    }
                }

x
 
RegisterReceiver(new ThreatEventReceiver(), new IntentFilter(""));
                
class ThreatEventReceiver : BroadcastReceiver
{
    public override void OnReceive(Context context, Intent intent)
    {
        // Message shown to the user
        String message = intent.GetStringExtra("message");
​
        // Threat detection cause
        String reasonData = intent.GetStringExtra("reasonData");
​
        // Event reason code
        String reasonCode = intent.GetStringExtra("reasonCode");
​
        // Current threat event score
        String currentThreatEventScore = intent.GetStringExtra("currentThreatEventScore");
​
        // Total threat events score
        String threatEventsScore = intent.GetStringExtra("threatEventsScore");
​
        // Replace '<Context Key>' with your specific event context key
        // String variable = intent.GetStringExtra("<Context Key>");
​
        // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
    }
}

                NSNotificationCenter.DefaultCenter.AddObserver(
                    (NSString)"", // Threat-Event Identifier
                    delegate (NSNotification notification)
                    {
                        // Message shown to the user
                        var message = notification.UserInfo.ObjectForKey("message");
                        
                        // Threat detection cause
                        var reasonData = notification.UserInfo.ObjectForKey("reasonData");
                        
                        // Event reason code
                        var reasonCode = notification.UserInfo.ObjectForKey("reasonCode");

                        // Current threat event score
                        var currentThreatEventScore = notification.UserInfo.ObjectForKey("currentThreatEventScore");
                        
                        // Total threat events score
                        var threatEventsScore = notification.UserInfo.ObjectForKey("threatEventsScore");

                        // Replace '' with your specific event context key
                        // var variable = notification.UserInfo.ObjectForKey("");

                        // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
                    }
                );

x
 
NSNotificationCenter.DefaultCenter.AddObserver(
    (NSString)"", // Threat-Event Identifier
    delegate (NSNotification notification)
    {
        // Message shown to the user
        var message = notification.UserInfo.ObjectForKey("message");
​
        // Threat detection cause
        var reasonData = notification.UserInfo.ObjectForKey("reasonData");
​
        // Event reason code
        var reasonCode = notification.UserInfo.ObjectForKey("reasonCode");
​
        // Current threat event score
        var currentThreatEventScore = notification.UserInfo.ObjectForKey("currentThreatEventScore");
​
        // Total threat events score
        var threatEventsScore = notification.UserInfo.ObjectForKey("threatEventsScore");
​
        // Replace '<Context Key>' with your specific event context key
        // var variable = notification.UserInfo.ObjectForKey("<Context Keys>");
​
        // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
    }
);

                window.broadcaster.addEventListener("", function(userInfo) {
                    var message = userInfo.message // Message shown to the user
                    var reasonData = userInfo.reasonData // Threat detection cause
                    var reasonCode = userInfo.reasonCode // Event reason code

                    // Current threat event score
                    var currentThreatEventScore = userInfo.currentThreatEventScore

                    // Total threat events score
                    var threatEventsScore = userInfo.threatEventsScore

                    // Replace '' with your specific event context key
                    // var variable = userInfo.

                    // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
                });

xxxxxxxxxx
 
window.broadcaster.addEventListener("", function(userInfo) {
    var message = userInfo.message // Message shown to the user
    var reasonData = userInfo.reasonData // Threat detection cause
    var reasonCode = userInfo.reasonCode // Event reason code
​
    // Current threat event score
    var currentThreatEventScore = userInfo.currentThreatEventScore
​
    // Total threat events score
    var threatEventsScore = userInfo.threatEventsScore
​
    // Replace '<Context Key>' with your specific event context key
    // var variable = userInfo.<Context Keys>
​
    // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
});

                import 'dart:async';
                import 'package:flutter/material.dart';
                import 'package:flutter/services.dart';

                class PlatformChannel extends StatefulWidget {
                    const PlatformChannel({super.key});

                    @override
                    State createState() => _PlatformChannelState();
                }

                class _PlatformChannelState extends State {
                    // Replace with your EventChannel name
                    static const String _eventChannelName = "";
                    static const EventChannel _eventChannel = EventChannel(_eventChannelName);

                    @override
                    void initState() {
                        super.initState();
                        _eventChannel.receiveBroadcastStream().listen(_onEvent, onError: _onError);
                    }

                    void _onEvent(Object? event) {
                        setState(() {
                            // Adapt this section based on your specific event data structure
                            var eventData = event as Map;

                            // Example: Accessing 'externalID' field from the event
                            var externalID = eventData['externalID'];

                            // Customize the rest of the fields based on your event structure
                            String message = eventData['message']; // Message shown to the user
                            String reasonData = eventData['reasonData']; // Threat detection cause
                            String reasonCode = eventData['reasonCode']; // Event reason code

                            // Current threat event score
                            String currentThreatEventScore = eventData['currentThreatEventScore'];

                            // Total threat events score
                            String threatEventsScore = eventData['threatEventsScore'];

                            // Replace '' with your specific event context key
                            // String variable = eventData[''];
                        });
                    }

                    // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
                }

x
 
import 'dart:async';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
​
class PlatformChannel extends StatefulWidget {
    const PlatformChannel({super.key});
​
    @override
    State<PlatformChannel> createState() => _PlatformChannelState();
}
​
class _PlatformChannelState extends State<PlatformChannel> {
    // Replace with your EventChannel name
    static const String _eventChannelName = "";
    static const EventChannel _eventChannel = EventChannel(_eventChannelName);
​
    @override
    void initState() {
        super.initState();
        _eventChannel.receiveBroadcastStream().listen(_onEvent, onError: _onError);
    }
​
    void _onEvent(Object? event) {
        setState(() {
            // Adapt this section based on your specific event data structure
            var eventData = event as Map;
​
            // Example: Accessing 'externalID' field from the event
            var externalID = eventData['externalID'];
​
            // Customize the rest of the fields based on your event structure
            String message = eventData['message']; // Message shown to the user
            String reasonData = eventData['reasonData']; // Threat detection cause
            String reasonCode = eventData['reasonCode']; // Event reason code
​
            // Current threat event score
            String currentThreatEventScore = eventData['currentThreatEventScore'];
​
            // Total threat events score
            String threatEventsScore = eventData['threatEventsScore'];
​
            // Replace '<Context Key>' with your specific event context key
            // String variable = eventData['<Context Keys>'];
        });
    }
​
    // Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
}

Using Appdome, there are no development or coding prerequisites to build secured Android Apps by using Obfuscate App Logic. There is no SDK and no library to code or implement in the app and no gateway to deploy in your network. All protections are built into each app and the resulting app is self-defending and self-protecting.

Releasing and Publishing Mobile Apps with Obfuscate App Logic

After successfully securing your app by using Appdome, there are several available options to complete your project, depending on your app lifecycle or workflow. These include:

Customizing, Configuring & Branding Secure Mobile Apps
Deploying/Publishing Secure mobile apps to Public or Private app stores
Releasing Secured Android & iOS Apps built on Appdome.

How Do I Learn More?

If you have any questions, please send them our way at support.appdome.com or via the chat window on the Appdome platform.

Thank you!

Thanks for visiting Appdome! Our mission is to secure every app on the planet by making mobile app security easy. We hope we’re living up to the mission with your project.

How to Obfuscate Kotlin Code in Android Apps

What is Kotlin?

Why does Kotlin Need its Own Obfuscation?

Prerequisites for Using Obfuscate App Logic:

Obfuscate App Logic on Android apps using Appdome

Upload the Mobile App to Appdome.

Upload an app to Appdome’s Mobile App Security Build System

Build the feature: Obfuscate App Logic.

Building Obfuscate App Logic by using Appdome’s DEV-API:

Building the Obfuscate App Logic feature via Appdome Console

Certify the Obfuscate App Logic feature in Android Apps

Using Threat-Events™ for App Logic Intelligence and Control in Android Apps

Related Articles:

How Do I Learn More?

Thank you!

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