Android Crackme and Structure offset propagation

Today we will look into the recently introduced feature in r2 - structure offset propagation. We will use it to solve a crackme based on reversing an Android JNI (Java Native Interface) library.Beware that the feature is still WIP and being constantly improved. This challenge is originally from NDH2012-wargame, so we are provided with an NDH.apk file, now after decompiling and using JD-GUI to browse through the code we can find some interesting functions :