My Short Experience with The Awesome DexGuard

gistfile1.txt

Hi, i would like to share my experience of using DexGuard (https://www.guardsquare.com/dexguard) as a premium obfuscator tool for Android APK. As we knew that apk is similar 
to zip and rar. It only wraps our project and there are a lot of tools that able to decompile apk. Even when devs have set proguard to 
the app they are still readable. This experience i got when i was training about android security, and i recommended the client to buy 
the DexGuard Lisence. The most expensive computer file that i have ever seen. They spent more than $4000 for 66 Mb and it's only to 
A SINGLE PACKAGE NAME !. 

I give you the sample, this is the Java File :
public class HelloWorldActivity extends AppCompatActivity
{
    private static final String MESSAGE = "Hello world!";


    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);

        TextView view = new TextView(this);
        view.setText(MESSAGE);
        view.setGravity(Gravity.CENTER);
        setContentView(view);

    }
}

And this is the output (after decompiling the apk) : 
public class HelloWorldActivity extends AppCompatActivity
{
  private static final byte[] ËŠ;
  private static int Ë‹ = 0;
  private static int ËŽ = 1;

  static
  {
    byte[] arrayOfByte = new byte[15];
    arrayOfByte[0] = 31;
    arrayOfByte[1] = -3;
    arrayOfByte[2] = -123;
    arrayOfByte[3] = -91;
    arrayOfByte[4] = -25;
    arrayOfByte[5] = -3;
    arrayOfByte[6] = 4;
    arrayOfByte[7] = 1;
    arrayOfByte[8] = 83;
    arrayOfByte[9] = -83;
    arrayOfByte[10] = 12;
    arrayOfByte[11] = 1;
    arrayOfByte[12] = 10;
    arrayOfByte[13] = 12;
    arrayOfByte[14] = 71;
    ËŠ = arrayOfByte;
  }

  // ERROR //
  private static java.lang.String ËŠ(int paramInt, byte paramByte1, byte paramByte2)
  {
    // Byte code:
    //   0: bipush 72
    //   2: iload_2
    //   3: iconst_3
    //   4: imul
    //   5: isub
    //   6: istore_3
    //   7: getstatic 29	com/example/HelloWorldActivity:ËŠ	[B
    //   10: astore 4
    //   12: iconst_0
    //   13: istore 5
    //   15: iconst_4
    //   16: iload_0
    //   17: iconst_2
    //   18: imul
    //   19: isub
    //   20: istore 6
    //   22: bipush 12
    //   24: iload_1
    //   25: iconst_3
    //   26: imul
    //   27: isub
    //   28: istore 7
    //   30: iload 7
    //   32: newarray byte
    //   34: astore 8
    //   36: iload 5
    //   38: istore 9
    //   40: iinc 5 1
    //   43: aload 8
    //   45: iload 9
    //   47: iload_3
    //   48: bastore
    //   49: iload 5
    //   51: iload 7
    //   53: if_icmpne +6 -> 59
    //   56: goto +155 -> 211
    //   59: goto +78 -> 137
    //   62: iconst_4
    //   63: iload_3
    //   64: iload 10
    //   66: isub
    //   67: iadd
    //   68: istore_3
    //   69: iinc 6 1
    //   72: goto +81 -> 153
    //   75: iconst_0
    //   76: istore 14
    //   78: goto +177 -> 255
    //   81: astore 17
    //   83: aload 17
    //   85: athrow
    //   86: iload 5
    //   88: istore 15
    //   90: iinc 5 1
    //   93: aload 8
    //   95: iload 15
    //   97: iload_3
    //   98: bastore
    //   99: iload 5
    //   101: iload 7
    //   103: if_icmpne +6 -> 109
    //   106: goto +105 -> 211
    //   109: goto +28 -> 137
    //   112: iconst_1
    //   113: istore 12
    //   115: goto +68 -> 183
    //   118: iconst_4
    //   119: iload_3
    //   120: iload 10
    //   122: isub
    //   123: iadd
    //   124: istore_3
    //   125: iinc 6 1
    //   128: goto +25 -> 153
    //   131: iconst_1
    //   132: istore 14
    //   134: goto +121 -> 255
    //   137: aload 4
    //   139: iload 6
    //   141: baload
    //   142: istore 10
    //   144: goto +82 -> 226
    //   147: iconst_0
    //   148: istore 12
    //   150: goto +33 -> 183
    //   153: bipush 33
    //   155: getstatic 15	com/example/HelloWorldActivity:ËŽ	I
    //   158: iadd
    //   159: istore 13
    //   161: iload 13
    //   163: sipush 128
    //   166: irem
    //   167: putstatic 13	com/example/HelloWorldActivity:Ë‹	I
    //   170: iload 13
    //   172: iconst_2
    //   173: irem
    //   174: ifeq +6 -> 180
    //   177: goto -46 -> 131
    //   180: goto -105 -> 75
    //   183: iload 12
    //   185: tableswitch	default:+23 -> 208, 0:+-67->118, 1:+-123->62
    //   209: impdep2
    //   210: if_icmpne -17664 -> -17454
    //   213: fload_3
    //   214: dup
    //   215: aload 8
    //   217: iconst_0
    //   218: invokespecial 40	java/lang/String:<init>	([BI)V
    //   221: astore 16
    //   223: aload 16
    //   225: areturn
    //   226: iconst_5
    //   227: getstatic 13	com/example/HelloWorldActivity:Ë‹	I
    //   230: iadd
    //   231: istore 11
    //   233: iload 11
    //   235: sipush 128
    //   238: irem
    //   239: putstatic 15	com/example/HelloWorldActivity:ËŽ	I
    //   242: iload 11
    //   244: iconst_2
    //   245: irem
    //   246: ifne +6 -> 252
    //   249: goto -137 -> 112
    //   252: goto -105 -> 147
    //   255: iload 14
    //   257: tableswitch	default:+23 -> 280, 0:+-221->36, 1:+-171->86
    //   281: impdep2
    //   282: baload
    //
    // Exception table:
    //   from	to	target	type
    //   211	223	81	java/lang/Exception
  }

  // ERROR //
  public void onCreate(android.os.Bundle paramBundle)
  {
    // Byte code:
    //   0: goto +8 -> 8
    //   3: astore 10
    //   5: aload 10
    //   7: athrow
    //   8: aload_0
    //   9: aload_1
    //   10: invokespecial 44	android/app/Activity:onCreate	(Landroid/os/Bundle;)V
    //   13: new 46	android/widget/TextView
    //   16: dup
    //   17: aload_0
    //   18: invokespecial 49	android/widget/TextView:<init>	(Landroid/content/Context;)V
    //   21: astore_2
    //   22: getstatic 29	com/example/HelloWorldActivity:ËŠ	[B
    //   25: bipush 7
    //   27: baload
    //   28: istore_3
    //   29: iload_3
    //   30: iconst_1
    //   31: isub
    //   32: i2b
    //   33: istore 4
    //   35: iload 4
    //   37: istore 5
    //   39: iload 5
    //   41: istore 6
    //   43: iload 4
    //   45: iload 5
    //   47: iload 6
    //   49: invokestatic 51	com/example/HelloWorldActivity:ËŠ	(IBB)Ljava/lang/String;
    //   52: astore 7
    //   54: aload 7
    //   56: invokevirtual 55	java/lang/String:intern	()Ljava/lang/String;
    //   59: astore 8
    //   61: aload_2
    //   62: aload 8
    //   64: invokevirtual 59	android/widget/TextView:setText	(Ljava/lang/CharSequence;)V
    //   67: aload_2
    //   68: bipush 17
    //   70: invokevirtual 63	android/widget/TextView:setGravity	(I)V
    //   73: aload_0
    //   74: aload_2
    //   75: invokevirtual 67	com/example/HelloWorldActivity:setContentView	(Landroid/view/View;)V
    //   78: aload_0
    //   79: ldc 69
    //   81: iconst_1
    //   82: invokestatic 75	android/widget/Toast:makeText	(Landroid/content/Context;Ljava/lang/CharSequence;I)Landroid/widget/Toast;
    //   85: astore 9
    //   87: aload 9
    //   89: invokevirtual 78	android/widget/Toast:show	()V
    //   92: return
    //   93: pop
    //   94: dload_3
    //   95: athrow
    //
    // Exception table:
    //   from	to	target	type
    //   8	13	3	java/lang/Exception
    //   13	13	3	java/lang/Exception
    //   13	22	3	java/lang/Exception
    //   22	29	3	java/lang/Exception
    //   43	54	3	java/lang/Exception
    //   54	61	3	java/lang/Exception
    //   61	67	3	java/lang/Exception
    //   67	73	3	java/lang/Exception
    //   73	78	3	java/lang/Exception
    //   78	87	3	java/lang/Exception
    //   87	92	3	java/lang/Exception
    //   13	13	93	java/lang/Exception
  }
}

/* Location:           C:\Users\inte\Downloads\APKtoJava_RC2\tools\classes-dex2jar.jar
 * Qualified Name:     com.example.HelloWorldActivity
 * JD-Core Version:    0.6.0
 */
I use ApkToJava RC2 to decompile the apk. And as you can see.. you can not see the codes inside the Activity.
As a Android Developer i could say that the dexguard does its job very well and it makes the reverse engineering process become harder
Hope in the future, Android Framework has a the same obsfucator tool to make our live easier. 

Thanks