How to Encrypt NSUserDefaults in iOS Apps

Last updated March 10, 2024 by Appdome

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.

Prerequisites for Using Encrypt In-App Preferences:

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

Encrypt In-App Preferences on iOS apps 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
    4. Encrypt In-App Preferences Compatible With: Obj-C, Java, Swift, Flutter, React Native, Unity, Xamarin, Cordova and more
  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:
      2. fusion set that contains Encrypt In-App Preferences

        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).

      3. 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.

      4. Open the Fusion Set Detail Summary by clicking the “...” symbol on the far-right corner of the Fusion Set. Copy 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, Circle 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: Check whether is toggled On (enabled), otherwise enable it . The feature Encrypt In-App Preferences is enabled by default, as shown below. 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.
        Encrypt In-App Preferences option

        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

        Fusion Set applied 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: Encrypt In-App Preferences 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 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

Using Threat-Events™ for In-App Preferences Intelligence and Control in iOS Apps

Appdome Threat-Events™ provides consumable in-app mobile app attack intelligence and defense control when In-App Preferences are detected. To consume and use Threat-Events™ for In-App Preferences in iOS Apps, use AddObserverForName in Notification Center, and the code samples for Threat-Events™ for In-App Preferences shown below.

The specifications and options for Threat-Events™ for In-App Preferences are:

Threat-Event™ Elements Encrypt In-App Preferences Method Detail
Appdome Feature Name Encrypt In-App Preferences
Threat-Event Mode
OFF, IN-APP DEFENSE Appdome detects, defends and notifies user (standard OS dialog) using customizable messaging.
ON, IN-APP DETECTION Appdome detects the attack or threat and passes the event in a standard format to the app for processing (app chooses how and when to enforce).
ON, IN-APP DEFENSE Uses Appdome Enforce mode for any attack or threat and passes the event in a standard format to the app for processing (gather intel on attacks and threats without losing any protection).
Certified Secure™ Threat Event Check x
Visible in ThreatScope™ x
Developer Parameters for Encrypting In-App Preferences Threat-Event™
Threat-Event NAME
Threat-Event DATA reasonData
Threat-Event CODE reasonCode
Threat-Event REF
Threat-Event SCORE
currentThreatEventScore Current Threat-Event score
threatEventsScore Total Threat-events score
Threat-Event Context Keys
message Message displayed for the user on event
failSafeEnforce Timed enforcement against the identified threat
externalID The external ID of the event which can be listened via Threat Events
osVersion OS version of the current device
deviceModel Current device model
deviceManufacturer The manufacturer of the current device
fusedAppToken The task ID of the Appdome fusion of the currently running app
kernelInfo Info about the kernel: system name, node name, release, version and machine.
deviceID Current device ID
reasonCode Reason code of the occurred event
buildDate Appdome fusion date of the current application
devicePlatform OS name of the current device
updatedOSVersion Is the OS version up to date
timeZone Time zone
deviceFaceDown Is the device face down
locationLong Location longitude conditioned by location permission
locationLat Location latitude conditioned by location permission
locationState Location state conditioned by location permission
wifiSsid Wifi SSID
wifiSsidPermissionStatus Wifi SSID permission status

With Threat-Events™ enabled (turned ON), iOS developers can get detailed attack intelligence and granular defense control in iOS applications and create amazing user experiences for all mobile end users when In-App Preferences are detected.

The following is a code sample for native iOS apps, which uses all values in the specification above for Encrypt In-App Preferences:


Using Appdome, there are no development or coding prerequisites to build secured iOS Apps by using Encrypt In-App Preferences. 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 Encrypt In-App Preferences

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:

How Do I Learn More?

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

Thank you!

Thanks for visiting Appdome! Our mission is to secure every app on the planet by making mobile app security easy. We hope we’re living up to the mission with your project.

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