Share via

Control Flow Obfuscation

  • Article

This process synthesizes branching, conditional, and iterative constructs that produce valid forward (executable) logic, but yield non-deterministic semantic results when decompilation is attempted. Control Flow obfuscation produces spaghetti logic that can be very difficult for a cracker to analyze. Consider the following example processed by Dotfuscator Professional Edition:

Original Source Code Before Obfuscation
© 2001, Microsoft Corporation
(Snippet from WordCount.cs C# example code)		 
public int CompareTo(Object o) {
    int n = occurrences – ((WordOccurrence)o).occurrences;
    if (n == 0) {
        n = String.Compare(word, ((WordOccurrence)o).word);
    }
    return(n);
}
Reverse-Engineered Source Code
After Control Flow Obfuscation
By Dotfuscator Professional Edition		 
public virtual int _a(Object A_0) {
    int local0;
    int local1;
    local0 = this.a – (c) A_0.a;
    if (local0 != 0) goto i0;
    goto i1;
    while (true) {
       return local1;
       i0: local1 = local0;
    }
    i1: local0 = System.String.Compare(this.b, (c) A_0.b);
    goto i0;
}

© 2002-2007 PreEmptive Solutions. All rights reserved.