How to Encrypt NSUserDefaults in iOS Apps

Learn to Encrypt In-App Preferences in iOS apps, in mobile CI/CD with a Data-Driven DevSecOps™ build system.

What are App Preferences (NSUserDefaults)?

In iOS app development, the NSUserDefaults class serves as an interface to the users’ defaults database, which allows an app to customize its behavior to match a user’s preferences. For example, you can allow users to specify their preferred units of measurement or media playback speed. Apps store these preferences by assigning key-value pairs to a set of parameters in a user’s defaults database, which maintain persistence across app launches.

Preferences are used for creating a sense of persistence and personalization for mobile users, in order to improve the user experience. Preferences are stored as plain-text data inside iOS apps and can be retrieved by other apps and systems.

Why Encrypt App Preferences in iOS apps?

Preferences can be any kind of text-based data that may include information about users that is highly personal, private or sensitive. For example, app preferences can be used for displaying a screen that contains a user’s preferred currency or type of credit card used to process transactions in an e-commerce app.  The use of app preferences is very broad and flexible, and there is no restriction on the type of information that can be stored in preferences and retrieved by other resources. Furthermore, App Preferences are stored as plain-text data (unencrypted) by default, which makes them an easy and target for hackers.

Encrypting In-App Preferences on iOS apps by Using Appdome

On Appdome, follow these 3 simple steps to create self-defending iOS Apps that Encrypt In-App Preferences 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. iOS Formats: .ipa

2. Build the feature: Encrypt In-App Preferences.

   1. Building Encrypt In-App Preferences by using Appdome’s DEV-API:

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

      Figure 1: Fusion Set that will contain the Encrypt In-App Preferences 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 In-App Preferences feature via Appdome Console, to add the Encrypt In-App Preferences 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 In-App Preferences feature via Appdome Console

      To build the Encrypt In-App Preferences 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) Encrypt In-App Preferences, 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 In-App Preferences.

         Figure 3: Encrypt In-App Preferences 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 In-App Preferences 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 In-App Preferences

         

         Figure 4: Fusion Set that displays the newly added Encrypt In-App Preferences protection

      4. Extra Configuration with Encrypt In-App Preferences:

         1. Encrypt In-App Preferences

            Encrypt NSUserDefaults.

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

   Congratulations!  The Encrypt In-App Preferences protection is now added to the mobile app

3. Certify the Encrypt In-App Preferences feature in iOS Apps.

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