flutter_secure_storage: App Crashes on Startup (Android 4.4)

App Crashes on Samsung Galaxy S3 Neo (Android 4.4). Exception in Logcat:

    Process: com.it_nomads.fluttersecurestorageexample, PID: 3794
    java.lang.VerifyError: com/it_nomads/fluttersecurestorage/ciphers/RSACipher18Implementation
        at com.it_nomads.fluttersecurestorage.ciphers.StorageCipher18Implementation.<init>(StorageCipher18Implementation.java:31)
        at com.it_nomads.fluttersecurestorage.FlutterSecureStoragePlugin.<init>(FlutterSecureStoragePlugin.java:46)
        at com.it_nomads.fluttersecurestorage.FlutterSecureStoragePlugin.registerWith(FlutterSecureStoragePlugin.java:33)
        at io.flutter.plugins.GeneratedPluginRegistrant.registerWith(GeneratedPluginRegistrant.java:14)
        at com.it_nomads.fluttersecurestorageexample.MainActivity.onCreate(MainActivity.java:12)
        at android.app.Activity.performCreate(Activity.java:5451)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2292)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2386)
        at android.app.ActivityThread.access$900(ActivityThread.java:169)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1277)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5476)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
        at dalvik.system.NativeStart.main(Native Method)

I think the problem is the StrongBoxUnavailableException in the createKeys method (RSACipher18Implementation). I tried to comment it out and it works, but I have no idea how to replace it properly.