Encrypted String

Encryption best practice

iOS and watchOS

Using ENCRYPTED_STRING and ENCRYPTED_STRING_IOS_WATCHOS guarantees that the plaintext of the list item values will not be included in the resulting application binary, only the ciphertext. The ciphertext can only be decrypted by Appfigurate using the correct private key.

You can verify that the plain text is not included in the RELEASE application binary using the macOS strings tool as follows:

Terminal

> cd ~/Library/Developer/Xcode/DerivedData/AppfigurateWorkspace-esajjxyazigjunfteipthjfiobut/Build/Products/Release-iphoneos/AppfigurateExample (iOS).app
> strings AppfigurateExample | grep "https://dev.appfigurate.io/list"     // no results
> strings AppfigurateExample | grep "H7o9Lgqd4RgMJ...rtJQGh8DiiSAQ=="     // prints H7o9Lgqd4RgMJ...rtJQGh8DiiSAQ==

It is best practice to use ENCRYPTED_STRING and ENCRYPTED_STRING_IOS_WATCHOS to encrypt sensitive information such as server urls (e.g. internal test environments), rather than expose them as plain text.

Android

Using a combination of BuildConfig.ENCRYPTED and ProGuard guarantees that the plaintext of the list item values will not be included in the resulting application binary, only the ciphertext. The ciphertext can only be decrypted by Appfigurate using the correct private key.

You can verify that the plaintext is not included in the RELEASE build variant APK or AAB using the macOS strings tool as follows:

Terminal

> cd AppfigurateExample/build/outputs/apk/release
> unzip AppfigurateExample-release.apk
> d2j-dex2jar -f classes.dex
> unzip classes-dex2jar.jar
> cd nz/co/electricbolt/appfigurateexample
> strings - ExampleConfiguration.class | grep "https://dev.appfigurate.io/list" // no results
> strings - ExampleConfiguration.class | grep "jm9SM4MEYa4FR...glwMGnpRI4JAQ==" // prints jm9SM4MEYa4FR...glwMGnpRI4JAQ==

The dex2jar tool can be installed using brew.

Mobile Flutter

The Appfigurate Flutter Plugin defers to the underlying native iOS app's APLConfiguration or Android app's nz.co.electricbolt.appfiguratelibrary.Configuration subclasses to read encrypted strings. Ensure you have read the encryption best practices for iOS and watchOS, and Android sections.

Objective-C (iOS, watchOS)

The default value of an encrypted NSString is nil. You must change the default value of the property by assigning a new plain text value in an overridden reset method.

@property(strong) NSString* propertyName;

This page describes encrypted strings. Appfigurate also supports plain textual strings.

NSString editable list implementation

ENCRYPTED_STRING_PROPERTY_LIST_EDIT(propertyName, regex, description, restart, ...)

The NSString property can be changed in Appfigurate by allowing the user to select from a predefined list of valid choices. The user can customize the list adding by additional values using a text field and a regular expression validating input.

Objective-C example

@import AppfigurateLibrary;

@interface Configuration : APLConfiguration

@property(nonatomic, strong) NSString* url;

@end

@implementation Configuration

ENCRYPTED_STRING_PROPERTY_LIST_EDIT(url, @"https://[\\w\\.-]+\\.appfigurate.io/.*", @"url", NO, @{
    @"Dev": ENCRYPTED_STRING_IOS_WATCHOS(@"https://dev.appfigurate.io/list",@"H7o9Lgqd4RgMJ...rtJQGh8DiiSAQ==",@""JaMa92a122zZs...Mnz23KamnZ0a="), 
    @"Test": ENCRYPTED_STRING_IOS_WATCHOS(@"https://test.appfigurate.io/list",@"PL+UtWB9WHuO7...aX5BdNqEcbmQE=",@"Na1MSadBCaDD...KKANZias199Km=="), 
    @"Prod": ENCRYPTED_STRING_IOS_WATCHOS(@"https://m.appfigurate.io/list",@"IxrJFFUarMg6p...E7OWYOC2uJ1AQ==",@"aZSDIMSaasiaM...8SKS1MMahfpIa=")});
...

Appfigurate UI element example

`ENCRYPTED_STRING` macro

ENCRYPTED_STRING(plaintext, ciphertext)

For an iOS app where the APLConfiguration subclass has one public key use the ENCRYPTED_STRING macro for each list item in the ENCRYPTED_STRING_PROPERTY_LIST_EDIT.

The first parameter of the ENCRYPTED_STRING macro is the plain text, and will be used by DEBUG builds. The second parameter of the ENCRYPTED_STRING macro is the ciphertext, and will be used by RELEASE builds. To generate the ciphertext, use the AppfigurateSE app or source editor extension for Xcode.

Objective-C example

ENCRYPTED_STRING_PROPERTY_LIST_EDIT(url, @"https://[\\w\\.-]+\\.appfigurate.io/.*", @"url", NO, @{
    @"Dev":ENCRYPTED_STRING(@"https://dev.appfigurate.io/list",@"H7o9Lgqd4RgMJ...rtJQGh8DiiSAQ=="), 
    @"Test":ENCRYPTED_STRING(@"https://test.appfigurate.io/list",@"PL+UtWB9WHuO7...aX5BdNqEcbmQE="), 
    @"Prod":ENCRYPTED_STRING(@"https://m.appfigurate.io/list",@"IxrJFFUarMg6p...E7OWYOC2uJ1AQ==")});

`ENCRYPTED_STRING_IOS_WATCHOS` macro

ENCRYPTED_STRING_IOS_WATCHOS(plaintext, ciphertextIOS, ciphertextWatchOS)

For an iOS and watchOS app where the APLConfiguration subclass has two public keys, use the ENCRYPTED_STRING_IOS_WATCHOS macro for each list item in the ENCRYPTED_STRING_PROPERTY_LIST_EDIT macro.

The first parameter of the ENCRYPTED_STRING macro is the plain text, and will be used by DEBUG builds. The second and third parameters of the ENCRYPTED_STRING macro are the ciphertext for iOS and watchOS apps, and will be used by RELEASE builds. To generate the ciphertext, use the AppfigurateSE app or source editor extension for Xcode.

Objective-C example

ENCRYPTED_STRING_PROPERTY_LIST_EDIT(url, @"https://[\\w\\.-]+\\.appfigurate.io/.*", @"url", NO, @{
    @"Dev": ENCRYPTED_STRING_IOS_WATCHOS(@"https://dev.appfigurate.io/list",@"H7o9Lgqd4RgMJ...rtJQGh8DiiSAQ==",@""JaMa92a122zZs...Mnz23KamnZ0a="), 
    @"Test": ENCRYPTED_STRING_IOS_WATCHOS(@"https://test.appfigurate.io/list",@"PL+UtWB9WHuO7...aX5BdNqEcbmQE=",@"Na1MSadBCaDD...KKANZias199Km=="), 
    @"Prod": ENCRYPTED_STRING_IOS_WATCHOS(@"https://m.appfigurate.io/list",@"IxrJFFUarMg6p...E7OWYOC2uJ1AQ==",@"aZSDIMSaasiaM...8SKS1MMahfpIa=")});

Swift (iOS, watchOS)

The default value of an encrypted String is nil. You must change the default value of the property by assigning a new plain text value in an overridden reset method.

This page describes encrypted strings. Appfigurate also supports plain textual strings.

String editable list implementation

@EncryptedStringPropertyListEdit(regex, description, encrypted, restart, values)
var propertyName: String

The String property can be changed in Appfigurate by allowing the user to select from a predefined list of valid choices. The user can customize the list adding by additional values using a text field and a regular expression validating input.

The encrypted parameter of EncryptedStringPropertyListEdit must be the result of calling the ENCRYPTED() function. e.g.

... description: "url", encrypted: ENCRYPTED(), restart: ...

Swift example

    @EncryptedStringPropertyListEdit(regex: #"https://[\w\.-]+\.appfigurate.io/.*"#, description: "url", encrypted: ENCRYPTED(), restart: false, values: [
        "Dev":ENCRYPTED_STRING_IOS_WATCHOS("https://dev.appfigurate.io/list","H7o9Lgqd4RgMJ...rtJQGh8DiiSAQ==","JaMa92a122zZs...Mnz23KamnZ0a="),
        "Test":ENCRYPTED_STRING_IOS_WATCHOS("https://test.appfigurate.io/list","PL+UtWB9WHuO7...aX5BdNqEcbmQE=","Na1MSadBCaDD...KKANZias199Km=="),
        "Prod":ENCRYPTED_STRING_IOS_WATCHOS("https://m.appfigurate.io/list","IxrJFFUarMg6p...E7OWYOC2uJ1AQ==","aZSDIMSaasiaM...8SKS1MMahfpIa=")])
    var url: String
    ...

Appfigurate UI element example

`ENCRYPTED_STRING` function

func ENCRYPTED_STRING(_ plaintext: String, _ ciphertext: String) -> String

For an iOS app where the APLConfiguration subclass has one public key use the ENCRYPTED_STRING function for each list item in the @EncryptedStringPropertyListEdit.

The first parameter of the ENCRYPTED_STRING function is the plaintext, and will be used by DEBUG builds. The second parameter of the ENCRYPTED_STRING macro is the ciphertext, and will be used by RELEASE builds. To generate the ciphertext, use the AppfigurateSE app or source editor extension for Xcode.

Swift example

    @EncryptedStringPropertyListEdit(regex: #"https://[\w\.-]+\.appfigurate.io/.*"#, description: "url", encrypted: ENCRYPTED(), restart: false, values: [
        "Dev":ENCRYPTED_STRING("https://dev.appfigurate.io/list","H7o9Lgqd4RgMJ...rtJQGh8DiiSAQ=="),
        "Test":ENCRYPTED_STRING("https://test.appfigurate.io/list","PL+UtWB9WHuO7...aX5BdNqEcbmQE="),
        "Prod":ENCRYPTED_STRING("https://m.appfigurate.io/list","IxrJFFUarMg6p...E7OWYOC2uJ1AQ==")])
    var url: String

`ENCRYPTED_STRING_IOS_WATCHOS` function

func ENCRYPTED_STRING_IOS_WATCHOS(_ plaintext: String, _ ciphertextIOS: String, _ ciphertextWatchOS: String) -> String

For an iOS and watchOS app where the APLConfiguration subclass has two public keys, use the ENCRYPTED_STRING_IOS_WATCHOS function for each list item in the @EncryptedStringPropertyListEdit.

The first parameter of the ENCRYPTED_STRING function is the plaintext, and will be used by DEBUG builds. The second and third parameters of the ENCRYPTED_STRING function are the ciphertext for iOS and watchOS apps, and will be used by RELEASE builds. To generate the ciphertext, use the AppfigurateSE app or source editor extension for Xcode.

Swift example

@EncryptedStringPropertyListEdit(regex: #"https://[\w\.-]+\.appfigurate.io/.*"#, description: "url", encrypted: ENCRYPTED(), restart: false, values: [
    "Dev":ENCRYPTED_STRING_IOS_WATCHOS("https://dev.appfigurate.io/list","H7o9Lgqd4RgMJ...rtJQGh8DiiSAQ==","JaMa92a122zZs...Mnz23KamnZ0a="),
    "Test":ENCRYPTED_STRING_IOS_WATCHOS("https://test.appfigurate.io/list","PL+UtWB9WHuO7...aX5BdNqEcbmQE=","Na1MSadBCaDD...KKANZias199Km=="),
    "Prod":ENCRYPTED_STRING_IOS_WATCHOS("https://m.appfigurate.io/list","IxrJFFUarMg6p...E7OWYOC2uJ1AQ==","aZSDIMSaasiaM...8SKS1MMahfpIa=")])
var url: String
...

`ENCRYPTED` function

func ENCRYPTED() -> Bool

Used in conjunction with the @EncryptedStringPropertyListEdit property wrapper. The encrypted parameter of @EncryptedStringPropertyListEdit must be the result of calling the ENCRYPTED() function. e.g.

... description: "url", encrypted: ENCRYPTED(), restart: ...

The function returns true if the calling app has been compiled in RELEASE mode or false if the calling app has been compiled in DEBUG mode.

Warning: This function will behave incorrectly if the apps build settings Swift compiler - Code generation ‣ Optimization Level is set to Optimize for Size (-Osize). The default Swift compiler optimization levels are No Optimization for DEBUG builds and Optimize for Speed -Ospeed for RELEASE builds. If you must use -Osize, then implement your own isEncrypted() style function as follows:

func isEncrypted() {
#if DEBUG
	return false
#else
	return true
#end
}

Then call your own isEncrypted() function instead of the provided ENCRYPTED() function e.g.

... description: "url", encrypted: isEncrypted(), restart: ...

Java (Android)

The default value of an encrypted String is null. You must change the default value of the property by assigning a new plaintext value in an overridden reset method.

This page describes encrypted strings. Appfigurate also supports plain textual strings.

`BuildConfig.ENCRYPTED` build constant

In your application's build.gradle:

Add the following into the android‣buildTypes‣debug section:
```
buildConfigField("boolean", "ENCRYPTED", "false")    
```
Add the following into the android‣buildTypes‣release section:
```
buildConfigField("boolean", "ENCRYPTED", "true")    
```
Ensure ProGuard runs on a Release build variant so that BuildConfig.ENCRYPTED == false dead code is stripped from the resulting APK or AAB (this will ensure the plaintext values are removed).

e.g.

apply plugin: 'com.android.application'

android {
    compileSdkVersion 32
    defaultConfig {
        ...
    }
    buildTypes {
        debug {
            debuggable true
            minifyEnabled false
            zipAlignEnabled false
            buildConfigField("boolean", "ENCRYPTED", "false")
        }
        release {
            minifyEnabled true
            shrinkResources true
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
            signingConfig signingConfigs.debug
            buildConfigField("boolean", "ENCRYPTED", "true")
        }
    }
}
...

Once you've modified build.gradle and synced the Gradle project, ensure the generated BuildConfig.java contains the following for a Debug build variant:

public static final boolean ENCRYPTED = false;

and the following for a Release build variant:

public static final boolean ENCRYPTED = true;

To generate the ciphertext, use the AppfigurateSE app.

String editable list implementation

@EncryptedStringPropertyListEdit(description, regularExpression, encrypted, restart)
String propertyName;

static Map<String, String> _propertyNameValues = new HashMap<>();

static {
    _propertyNameValues.put("key1", BuildConfig.ENCRYPTED ? "cipher1" : "plain1");
}

public Map<String, String> propertyNameValues() {
    return _propertyNameValues;
}

The encrypted parameter of EncryptedStringPropertyListEdit must be the result of calling BuildConfig.ENCRYPTED. e.g.

     ... description = "url", encrypted = BuildConfig.ENCRYPTED, restart = ...

You must implement a method with the same name as the property, but ending with Values. e.g. if your property name is url, your method must be named urlValues. The method must return a Map<String, String> of the possible property values.

Java example

import nz.co.electricbolt.appfiguratelibrary.Configuration;
import nz.co.electricbolt.appfiguratelibrary.annotations.EncryptedStringPropertyListEdit;

public class AppConfiguration extends Configuration {

    @EncryptedStringPropertyListEdit(description: "url", regularExpression = "https://[\w\.-]+\.appfigurate.io/.*", encrypted = BuildConfig.ENCRYPTED, restart = false)
    String url;
    
    static Map<String, String> _urlValues = new HashMap<>();

    static {
        _urlValues("Dev", BuildConfig.ENCRYPTED ? "H7o9Lgqd4RgMJ...rtJQGh8DiiSAQ==" : "https://dev.appfigurate.io/list");
        _urlValues("Test", BuildConfig.ENCRYPTED ? "PL+UtWB9WHuO7...aX5BdNqEcbmQE=" : "https://test.appfigurate.io/list");
        _urlValues("Prod", BuildConfig.ENCRYPTED ? "IxrJFFUarMg6p...E7OWYOC2uJ1AQ==" : "https://m.appfigurate.io/list");
    }

    public Map<String, String> urlValues() {
        return _urlValues;
    } 
...

Appfigurate UI element example

Kotlin (Android)

The default value of an encrypted String is null. You must change the default value of the property by assigning a new plaintext value in an overridden reset method.

This page describes encrypted strings. Appfigurate also supports plain textual strings.

`BuildConfig.ENCRYPTED` build constant

In your application's build.gradle:

Add the following into the android‣buildTypes‣debug section:
```
buildConfigField("boolean", "ENCRYPTED", "false")    
```
Add the following into the android‣buildTypes‣release section:
```
buildConfigField("boolean", "ENCRYPTED", "true")    
```
Ensure ProGuard runs on a Release build variant so that BuildConfig.ENCRYPTED == false dead code is stripped from the resulting APK or AAB (this will ensure the plaintext values are removed).

e.g.

apply plugin: 'com.android.application'

android {
    compileSdkVersion 32
    defaultConfig {
        ...
    }
    buildTypes {
        debug {
            debuggable true
            minifyEnabled false
            zipAlignEnabled false
            buildConfigField("boolean", "ENCRYPTED", "false")
        }
        release {
            minifyEnabled true
            shrinkResources true
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
            signingConfig signingConfigs.debug
            buildConfigField("boolean", "ENCRYPTED", "true")
        }
    }
}
...

Once you've modified build.gradle and synced the Gradle project, ensure the generated BuildConfig.java contains the following for a Debug build variant:

public static final boolean ENCRYPTED = false;

and the following for a Release build variant:

public static final boolean ENCRYPTED = true;

To generate the ciphertext, use the AppfigurateSE app.

String editable list implementation

@EncryptedStringPropertyListEdit(description, regularExpression, encrypted, restart)
var propertyName: String? = null

companion object {
    var _propertyNameValues: MutableMap<String, String> = HashMap()

    init {
        _propertyNameValues["key1"] = if (BuildConfig.ENCRYPTED) "cipher1" else "plain1"
    }
}

fun propertyNameValues(): Map<String, String> {
    return _propertyNameValues;
}

The encrypted parameter of EncryptedStringPropertyListEdit must be the result of calling BuildConfig.ENCRYPTED. e.g.

     ... description = "url", encrypted = BuildConfig.ENCRYPTED, restart = ...

You must implement a method with the same name as the property, but ending with Values. e.g. if your property name is url, your method must be named urlValues. The method must return a Map<String, String> of the possible property values.

Kotlin example

import nz.co.electricbolt.appfiguratelibrary.Configuration
import nz.co.electricbolt.appfiguratelibrary.annotations.EncryptedStringPropertyListEdit

class AppConfiguration : Configuration() {

    @EncryptedStringPropertyListEdit(description = "url", regularExpression = "https://[\w\.-]+\.appfigurate.io/.*", encrypted = BuildConfig.ENCRYPTED, restart = false)
    var url: String? = null
    
    companion object {
        var _urlValues: MutableMap<String, String> _urlValues = HashMap()  

        init {
            _urlValues["Dev"] = if (BuildConfig.ENCRYPTED) "H7o9Lgqd4RgMJ...rtJQGh8DiiSAQ==" else "https://dev.appfigurate.io/list"
            _urlValues["Test"] = if (BuildConfig.ENCRYPTED) "PL+UtWB9WHuO7...aX5BdNqEcbmQE=" else "https://test.appfigurate.io/list"
            _urlValues["Prod"] = if (BuildConfig.ENCRYPTED) "IxrJFFUarMg6p...E7OWYOC2uJ1AQ==" else "https://m.appfigurate.io/list"
        }
    }

    fun urlValues(): Map<String, String> {
        return _urlValues
    } 
...

Appfigurate UI element example

Dart (Flutter for iOS, Flutter for Android)

The flutter APLNativeConfiguration class defers to the underlying platform APLConfiguration (iOS) or nz.co.electricbolt.appfiguratelibrary.Configuration (Android) subclass to read property values.

The underlying platform property value can either be a plain textual string or an encrypted string.

String implementation

String get propertyName => nativeString('propertyName');

Dart example

import 'package:appfigurateflutter/appfigurateflutter.dart';

public class Configuration extends APLNativeConfiguration {

    String get foregroundColorHex => nativeString('foregroundColorHex');
    ...

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Last updated 6 months ago

Encryption best practice

iOS and watchOS

Android

Mobile Flutter

Objective-C (iOS, watchOS)

NSString editable list implementation

ENCRYPTED_STRING macro

ENCRYPTED_STRING_IOS_WATCHOS macro

Swift (iOS, watchOS)

String editable list implementation

ENCRYPTED_STRING function

ENCRYPTED_STRING_IOS_WATCHOS function

ENCRYPTED function

Java (Android)

BuildConfig.ENCRYPTED build constant

String editable list implementation

Kotlin (Android)

BuildConfig.ENCRYPTED build constant

String editable list implementation

Dart (Flutter for iOS, Flutter for Android)

String implementation

`ENCRYPTED_STRING` macro

`ENCRYPTED_STRING_IOS_WATCHOS` macro

`ENCRYPTED_STRING` function

`ENCRYPTED_STRING_IOS_WATCHOS` function

`ENCRYPTED` function

`BuildConfig.ENCRYPTED` build constant

`BuildConfig.ENCRYPTED` build constant