How to Encrypt NSUserDefaults in iOS Apps

Last updated August 16, 2022 by Appdome

Learn to Encrypt 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 App Preferences on iOS apps by Using Appdome

On Appdome, follow these 3 simple steps to create self-defending iOS Apps that Encrypt 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 Protection: Data at Rest Encryption.

    1. Building Data at Rest Encryption by using Appdome’s DEV-API:

      1. Create and name the Fusion Set (security template) that will contain the Data at Rest Encryption feature as shown below:
      2. fusion set that contains Data at Rest Encryption

        Figure 1: Fusion Set that will contain the Data at Rest Encryption 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 Data at Rest Encryption feature via Appdome Console, to add the Data at Rest Encryption 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, 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 Data at Rest Encryption feature via Appdome Console

      To build the Data at Rest Encryption 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) Data at Rest Encryption, as shown below. Data at Rest Encryption option

        Figure 3: Encrypt App Preferences option

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

        Fusion Set applied Data at Rest Encryption

        Figure 4: Fusion Set that displays the newly added Data at Rest Encryption protection

      4. Extra Configuration with Data at Rest Encryption:
        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 Data at Rest Encryption protection is now added to the mobile app
  3. Certify the Data at Rest Encryption feature in iOS Apps.

    After building Data at Rest Encryption, Appdome generates a Certified Secure™ certificate to guarantee that the Data at Rest Encryption protection has been added and is protecting the app. To verify that the Data at Rest Encryption protection has been added to the mobile app, locate the protection in the Certified Secure™ certificate as shown below: Data at Rest Encryption shown in Certificate secure

    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 Data at Rest Encryption has been added to each iOS app. Certified Secure provides instant and in-line DevSecOps compliance certification that Data at Rest Encryption and other mobile app security features are in each build of the mobile app

Prerequisites to Using Data at Rest Encryption:

To use Appdome’s mobile app security build system to Encrypt App Preferences , you’ll need:

Using Appdome, there are no development or coding prerequisites to build secured Apps by using Data at Rest Encryption. 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 Data at Rest Encryption

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:

All apps protected by Appdome are fully compatible with any public app store, including Apple App Store, Google Play, Huawei App Gallery and more.

Protections Similar to Data at Rest Encryption

If you have any questions, please send them our way at or via the chat window on the Appdome platform.

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