How to Obfuscate Java Code in Android Apps

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

What is Java Code in Android Apps?

Java is a programming language used in mobile app development for building Android apps. Java code consists of human-readable instructions that define the app’s functionality. These instructions use clear terms like “if,” “for,” and meaningful names for methods (functions) and variables (data holders). However, during the build process, this Java code gets compiled into bytecode, a lower-level language understood by the Java Virtual Machine (JVM), an intermediate format that the Android system interprets. Bytecode offers no protection, making it highly susceptible to reverse engineering by tools such as Smali and JADX, which take the Java source code and decompile it into a readable format that allows attackers to examine an app’s functionality and behavior. This can be risky, especially for apps that handle sensitive data or have unique algorithms.

Why Does Java Need it's Own Obfuscation?

Once an attacker has access to the .dex files (containing the bytecode), they can potentially reverse-engineer the logic behind your app and expose your intellectual property and core functionalities. Obfuscation is a security technique that deliberately obscures the internal workings of your code without affecting its functionality. Appdome’s Obfuscate App Logic feature involves renaming methods, functions, variables, and classes within the bytecode. These originally clear and descriptive names are replaced with cryptic characters, making it significantly more challenging to understand the app’s logic by simply looking at the bytecode. This process is essential in preventing attackers from using static code analysis to dissect the application’s functionality, ensuring the security and integrity of the app’s business logic, and protecting intellectual property. Through obfuscation, developers can significantly mitigate the risks associated with code tampering and piracy, preserving the application’s reliability and user trust.

In addition to Obfuscate App Logic, app developers can choose to enforce Appdome’s Dex File Encryption feature. However, it is important to note that Dex File Encryption may cause latency issues. To reduce the latency, we recommend managing the amount of code you’re encrypting.

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 3 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:
      

      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).

      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, as shown in Figure 1 above, and get 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, Cirlce 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.

         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. How: Toggle (turn ON) Obfuscate App Logic, as shown below.

         Figure 3: Obfuscate App Logic option

      3. When you select the 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

      4. 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

3. 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