How to Encrypt Assets & Resources in Android Apps

Learn to Encrypt assets & resources in Android apps, in mobile CI/CD with a Data-Driven DevSecOps™ build system.

What are Application Resources?

In Android apps, the Assets and res directories are places where the developer can add arbitrary files like text files, XML, HTML, fonts, music, and video in the application. These files, which are necessary for the app’s functionality and performance, are stored in the device under the assets folder of the application and are used during runtime.

Why Should Developers Encrypt Application Resources in their Android Apps?

Users with privileged user access can easily read the resource’s contents. Appdome can encrypt these files using modern and standardized AES encryption, rendering them unreadable for malicious application users. The resources are decrypted when the application uses them to make sure that the app’s functionality doesn’t change. Potential attackers can easily access resources, and the resources include databases, texts, and other files that may contain sensitive information. Therefore, Encrypting Application Resources hardens the security of that information.

Prerequisites for Using Encrypt Resources:

To use Appdome’s mobile app security build system to Encrypt assets & resources , you’ll need:

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

Encrypt assets & resources on Android apps using Appdome

On Appdome, follow these 3 simple steps to create self-defending Android Apps that Encrypt assets & resources 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. Encrypt Resources Compatible With: Java, JS, C++, C#, Kotlin, Flutter, React Native, Unity, Xamarin, Cordova and other Android apps

2. Build the feature: Encrypt Resources.

   1. Building Encrypt Resources by using Appdome’s DEV-API:

      1. Create and name the Fusion Set (security template) that will contain the Encrypt Resources feature as shown below:
      

      Figure 1: Fusion Set that will contain the Encrypt Resources 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 Encrypt Resources feature via Appdome Console, to add the Encrypt Resources 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 Encrypt Resources feature via Appdome Console

      To build the Encrypt Resources protection by using Appdome Console, follow the instructions below.

      1. Where: Inside the Appdome Console, go to Build > Security Tab > TOTALData™ Encryption section.

         Like all other options in ONEShield™, Encrypt Resources is turned on by default, as shown below:

         Figure 3: Encrypt Resources 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) Encrypt Resources, as shown below.
         If needed, Customize the Threat Notification to be displayed to the mobile end-user in a standard OS dialog notification when Appdome Encrypts assets & resources.

         Figure 3: Encrypt assets & resources 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.

      3. When you select the Encrypt Resources you'll notice that your Fusion Set you created in step 2.1.1 now bears the icon of the protection category that contains Encrypt Resources

         

         Figure 4: Fusion Set that displays the newly added Encrypt Resources protection

      4. Click Build My App at the bottom of the Build Workflow (shown in Figure 3).

   Congratulations!  The Encrypt Resources protection is now added to the mobile app

3. Certify the Encrypt Resources feature in Android Apps.

   After building Encrypt Resources, Appdome generates a Certified Secure™ certificate to guarantee that the Encrypt Resources protection has been added and is protecting the app. To verify that the Encrypt Resources 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 Encrypt Resources has been added to each Android app. Certified Secure provides instant and in-line DevSecOps compliance certification that Encrypt Resources and other mobile app security features are in each build of the mobile app