Android 04
This exercise will guide you through the process of reversing a simple Android code
In this challenge, you are tasked with retrieving a key from an Android application that prompts for a pin code. However, the pin code is not set, making it impossible to retrieve the key through normal means. There are two methods to approach this exercise: using apktool to decompile and inspect the smali code, or manually extracting the classes.dex file from the APK, converting it to a JAR file with dex2jar, and decompiling it using jd-gui to inspect the Java code.
By examining the decompiled code, you will find that the key has been "encrypted" using a simple XOR operation with a single character. Understanding this, you can write a script to reverse the XOR operation and retrieve the clear text key. This exercise will help you gain practical experience in reverse engineering Android applications and understanding basic encryption techniques.