How to Prevent Java Decoding to Protect Android apps

Last updated May 28, 2023 by Appdome

Learn to Prevent Java Decoding in Android apps, in mobile CI/CD with a Data-Driven DevSecOps™ build system.

What is Java Decoding?

You can use Appdome to Prevent Java Decoding to Protect Android apps. Java Decoding is a method of reverse engineering, where hackers use open-source decompilers such as Jadx to discover and display the original Java source code of an app.

Such tools operate by taking the dex files of an already compiled .apk file, converting them to Smali code and then displaying the Smali code in a form similar to a human-readable Java code.

How does Appdome prevent Java Decoding?

Appdome uses advanced dex manipulation techniques to obfuscate and complicate logic code blocks, making it harder for open-source decompilers such as Jadx to read the dex and translate it to readable Java code. Appdome ensures that the performance of the app is not hindered by the dex manipulation and only affects static code decompilers that the code should be protected from.

Enabling (toggling On) the Anti-Reverse Engineering and enabling the Anti Java decoding sub toggle, automatically prevents the use of decompilers and other reverse engineering tools to perform Java decoding.

Prerequisites for Using Anti Java Decoding:

To use Appdome’s mobile app security build system to Prevent Java Decoding , you’ll need:

Prevent Java Decoding on Android apps using Appdome

On Appdome, follow these simple steps to create self-defending Android Apps that Prevent Java Decoding 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. Anti Java Decoding Compatible With: Java, JS, C++, C#, Kotlin, Flutter, React Native, Unity, Xamarin, Cordova and other Android apps
  2. Build the feature: Anti Java Decoding.

    1. Building Anti Java Decoding by using Appdome’s DEV-API:

      1. Create and name the Fusion Set (security template) that will contain the Anti Java Decoding feature as shown below:
      2. fusion set that contains Anti Java Decoding

        Figure 1: Fusion Set that will contain the Anti Java Decoding 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 Anti Java Decoding feature via Appdome Console, to add the Anti Java Decoding 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 Anti Java Decoding feature via Appdome Console

      To build the Anti Java Decoding protection by using Appdome Console, follow the instructions below.

      1. Where: Inside the Appdome Console, go to Build > Security Tab > Anti-Reverse Engineering 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 Anti Java Decoding

        Fusion Set applied Anti Java Decoding

        Figure 4: Fusion Set that displays the newly added Anti Java Decoding protection

      3. Click Build My App at the bottom of the Build Workflow (shown in Figure 3).
    Congratulations!  The Anti Java Decoding protection is now added to the mobile app

Using Threat-Events™ for Java Decoding Intelligence and Control in Android Apps

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

The specifications and options for Threat-Events™ for Java Decoding are:

Threat-Event™ Elements Prevent Java Decoding Method Detail
Appdome Feature Name Anti Java Decoding
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
Visible in ThreatScope™
Developer Parameters for Preventing Java Decoding Threat-Event™
Threat-Event NAME Java Decoding
Threat-Event DATA reasonData
Threat-Event CODE reasonCode
Threat-Event REF 6801
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 Java Decoding is detected.

The following is a code sample for native Android apps, which uses all values in the specification above for Anti Java Decoding:

Using Appdome, there are no development or coding prerequisites to build secured Android Apps by using Anti Java Decoding. 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 Anti Java Decoding

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 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.

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