Obfuscation techniques in Java Therese Berge Jonas Ringedal

Presentation Goal of the project Background Obfuscation techniques Tests Evaluation and results

Goal of the project Gain knowledge about different obfuscation techniques Find the best technique for us –Testing existing programs –Evaluating the techniques

Background Java increased the threat of reverse engineering –High-level bytecode –Platform independent Portable Anyone can have access to the bytecode Reverse engineering –Analyse system to create higher level representation –Recreate Java source code

Obfuscation techniques Layout Obfuscation Data Obfuscation Control Obfuscation Preventative Transformations

Layout Obfuscation Changing variables Removing comments Both methods: –Free of cost –One way functions

Data Obfuscation Encoding for(int i = 0; i < 100; i++ ){} f(i) = 2*i+5 for(int i = 5; i < 205; i =i+2){} Split array Change ordering –Variable declaration spread out

Hide information flow –Dead code –Parallelize Code Control Obfuscation

Preventative Transformations Crash deobfuscators –Use known weaknesses Stealth Hide obfuscation

Tests Obfuscator: JShrink Decompiler: JAD Test code: Password.java Test results JShrink JAD from.class JAD from obfuscated code

Evaluation and results Obfuscators major tools for protecting Java programs from reverse engineering Hard to find free programs Layout Obfuscation not enough Best: Combination of manually changed code, stealth and obfuscators. Goal achieved