How to Encrypt Strings.xml in Android Apps

Learn to Encrypt strings under strings.xml in Android apps, in mobile CI/CD with a Data-Driven DevSecOps™ build system.

What is the strings.xml file?

The strings.xml file is the usual location for storing a string resource, which provides text strings for your application, with optional text styling and formatting. Unlike the java strings and the assets folder, the string resources cannot be encrypted on the device because the OS needs to access the strings file. This makes strings the soft belly of any application, as they can contain sensitive information such as phrases, URLs, tokens, and passwords that can be easily understood from the application without using any specialized tools.

How does Appdome Protect the strings.xml File?

To provide customers with overall security protection of their Android app, Appdome’s XMLEncrypt™ service encrypts the sensitive strings stored in the localizable locations in Android.

Encrypt strings under strings.xml on Android apps using Appdome

On Appdome, follow these 3 simple steps to create self-defending Android Apps that Encrypt strings under strings.xml 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. XMLEncrypt™ Compatible With: Java, JS, C++, C#, Kotlin, Flutter, React Native, Unity, Xamarin, Cordova and more

2. Build the feature: XMLEncrypt™.

   1. Building XMLEncrypt™ by using Appdome’s DEV-API:

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

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

      To build the XMLEncrypt™ protection by using Appdome Console, follow the instructions below.

      1. Where: Inside the Appdome Console, go to Build > Security Tab > TOTALData™ Encryption section
      2. How: Toggle (turn ON) XMLEncrypt™, 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 strings under strings.xml .

         Figure 3: Encrypt strings under strings.xml 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 XMLEncrypt™ you'll notice that your Fusion Set you created in step 2.1.1 now bears the icon of the protection category that contains XMLEncrypt™

         

         Figure 4: Fusion Set that displays the newly added XMLEncrypt™ protection

      4. Extra Configuration with XMLEncrypt™:

         1. XMLEncrypt™

            Encrypt sensitive strings.xml values for all locales.

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

   Congratulations!  The XMLEncrypt™ protection is now added to the mobile app

3. Certify the XMLEncrypt™ feature in Android Apps.

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