Android KeyStore crashes in Android Instant App - kotlin

Question

val masterKey =
MasterKey
.Builder(applicationContext)
.setKeyScheme(MasterKey.KeyScheme.AES256_GCM)
.build()
Running this code in an Instant App crashes my app with the following Stack Trace:
2020-12-21 13:07:29.654 28949-28949/com.example.instantappandroidkeystore E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.instantappandroidkeystore, PID: 28949
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.instantappandroidkeystore/com.example.instantappandroidkeystore.MainActivity}: java.lang.NullPointerException: Attempt to invoke interface method 'int android.security.keystore.IKeystoreService.exist(java.lang.String, int)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3448)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3595)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2147)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:237)
at android.app.ActivityThread.main(ActivityThread.java:7814)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1068)
Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'int android.security.keystore.IKeystoreService.exist(java.lang.String, int)' on a null object reference
at android.security.KeyStore.contains(KeyStore.java:408)
at android.security.keystore.AndroidKeyStoreSpi.engineContainsAlias(AndroidKeyStoreSpi.java:1038)
at java.security.KeyStore.containsAlias(KeyStore.java:1293)
at androidx.security.crypto.MasterKeys.keyExists(MasterKeys.java:154)
at androidx.security.crypto.MasterKeys.getOrCreate(MasterKeys.java:96)
at androidx.security.crypto.MasterKey$Builder.buildOnM(MasterKey.java:357)
at androidx.security.crypto.MasterKey$Builder.build(MasterKey.java:314)
at com.example.instantappandroidkeystore.MainActivity.onCreate(MainActivity.kt:32)
at android.app.Activity.performCreate(Activity.java:7955)
at android.app.Activity.performCreate(Activity.java:7944)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1307)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3423)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3595) 
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83) 
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2147) 
at android.os.Handler.dispatchMessage(Handler.java:107) 
at android.os.Looper.loop(Looper.java:237) 
at android.app.ActivityThread.main(ActivityThread.java:7814) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1068) 
I have no luck finding this issue in StackOverflow, but I have found it in Google Issue Tracker, but with no response. So I created submitted an issue to Google with more information. https://issuetracker.google.com/issues/176085956
Has anyone encounter this issue and was able to solve it.
My working environment is:
Mac OS 10.15.7
Android Studio 4.0.1
Samsung A70
Android version 10

Answer 1

While this is not documented formally on developer.android forum, looks like AndroidKeyStore access is restricted for instant apps. I came across this link https://www.reddit.com/r/androiddev/comments/7a4tdw/why_no_hardware_backed_keystore_in_instant_apps/
This is quite strange that keystore is restricted and no android documentation explains it. I am not sure on an alternative to accessing KeyStore as we have lot of dependency on keystore for our regular app (non instant) and I can't think of a better option. Looking forward for suggestions !