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:

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:

  1. 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
  2. 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. fusion set that contains Obfuscate App Logic

        Figure 1: Fusion Set that will contain the Obfuscate App Logic feature
        Note: Naming the Fusion Set to correspond to the protection(s) selected is for illustration purposes only (not required).

      3. 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.

      4. Open the Fusion Set Detail Summary by clicking the “...” symbol on the far-right corner of the Fusion Set, as shown in Figure 1 above, and get the Fusion Set ID from the Fusion Set Detail Summary (as shown below): fusion Set Detail Summary image

        Figure 2: Fusion Set Detail Summary
        Note: Annotating the Fusion Set to identify the protection(s) selected is optional only (not mandatory).

      5. 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:
        1. Build an API for the app – for instructions, see the tasks under Appdome API Reference Guide
        2. 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.
      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

        Fusion Set applied 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

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
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
deviceID Current device ID
reasonCode Reason code of the occured event
buildDate Appdome fusion date of the current application
devicePlatform OS name of the current device
carrierName Carrier name of the current device
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:


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:

Related Articles:

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!

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