This.f1700 = new C0457( this, null, "my_prefs.xml") Ĭode snippet 2: App.java decompiled with jadx after applying name obfuscation String encryptionĮncryption is another obfuscation technique that a decompiler can’t overcome. Such techniques can only aim to change the identifiers to more readable names, but they can’t recover the original identifiers since these are completely stripped from the binary. Others use standard names like Class001, Class002 etc. Some decompilers, like Deguard, try to overcome this problem by performing pattern recognition and semantic analysis to guess possible identifier names. This.ˊ = new ᴮ( this, null, "my_prefs.xml") Ĭode snippet 1: App.java decompiled with JD-GUI after applying name obfuscation We get comparable results when we use CFR or Proycon. When we apply name obfuscation to the App.java class and try to decompile it with JD-GUI, we see that the output no longer contains any semantic information. This technique consists in replacing the names of classes, fields, methods and resources with meaningless characters to make the code of application more difficult to read and interpret. Renaming identifiers is a simple but powerful obfuscation technique. We focus on three techniques: name obfuscation, string encryption and control flow obfuscation. To illustrate what code hardening does, we analyze a sample application (App.java) protected with DexGuard using basic and popular reverse engineering tools. In some cases, it changes the bytecode so significantly that it’s impossible to revert it back to its original form.
It transforms the code through various techniques without affecting the functionality to make it obscure and unintelligible. Once an attacker has retrieved the source code, he is able to steal parts of it, extract valuable information from it or modify it.Ĭode hardening (obfuscation and encryption) is an effective way of protecting mobile applications against reverse engineering. These tools are used to dump the executable code and, in some cases, reconstruct the source code.
Android applications can be reverse engineered using a host of freely available tools such as Apktool, dex2jar, dexdump, Jadx, JD-GUI, CFR and Procyon.
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