Most secure way to store strings and use for later

I am developing an app where I need to store two strings for later use . I used sharedpreferences for that . But later I found that this is not secure enough . For rooted phones it is very easy to get the preferences and there are other processes too . I'm finding a secure way to store these two strings so that any app can't access those even if the phone is rooted . These strings will to totally invisible to other apps .

I would look into the Android Keystore Subsystem for that. Normally you would use the Keystore to store a symmetric key and then use that stored key with AES (or something similar) to encrypt/decrypt the data.