Click here to Skip to main content
13,634,012 members
Click here to Skip to main content
Add your own
alternative version

Tagged as

Stats

9K views
42 bookmarked
Posted 22 May 2018
Licenced Ms-PL

Protect your Source Code from Decompiling or Reverse Engineering

, 22 May 2018
Rate this:
Please Sign up or sign in to vote.
How to protect your source code from decompiling or reverse engineering

Many developers are still not aware that Portable Executable (PE) files can be decompiled to readable source code. Before learning how to prevent or make it hard for the decompilers to reverse engineer the source code, we need to understand a few basics concepts.

What is a Portable Executable File?

When source code is complied, it generates a Portable Executable (PE) file. Portable Executable (PE) is either a DLL or an EXE. PE file contains MSIL (Microsoft Intermediate Language) and Metadata. MSIL is ultimately converted by CLR into the native code which a processor can understand. Metadata contains assemble information like Assembly Name, Version, Culture and Public Key.

How Can We Get Source Code from DLL or EXE?

Yes, we can get the source code from DLL or EXE. To demonstrate this, let's create a simple application first.

Open Visual Studio, create a new project and select console based application.

image

Add some sample code into the Program.cs:

using System;
 
namespace MyConsoleApp
{
  internal class Program
  {
    private static void Main(string[] args)
    {
      Console.WriteLine(PublicMethod());
      Console.WriteLine(PrivateMethod());
    }
 
    public static string PublicMethod()
    {
      // Your source code here
      return "Public Method";
    }
 
    private static string PrivateMethod()
    {
      // Your source code here
      return "Private Method";
    }
  }
}

Now build the application, an EXE will be generated in the bin/debug folder:

image

Now let's try to get the source code from the EXE file. For the first, open Visual Studio command prompt.

image

Type ildasm and hit enter. IL DASM is MSIL Disassembler. It basically has an ability to read Intermediate Language.

image

IL DASM will open, now open the EXE file we created.

image

As we can see, IL DASM disassembles the EXE and lots of useful information can be retrieved, though it does not provide the original source code completely, a lot can be interpreted. The easy way to reverse engineer and get the exact source code there are decompilers available in the market for free such as Telerik JustDecompile and Jet Brains dotPeek through which we can convert the Intermediate Language into the original source code.

image

As we can see in the above screenshot when we open the EXE with Telerik JustDecompile, we are able to see the original source code, this can lead to piracy and ultimately you can lose your profits.

How to Prevent EXE and DLL from Getting Decompiled?

The process of protecting the EXE and DLL from getting decompiled into the original source code is called Obfuscation. There are a lot of paid and free software available to Obfuscate the .NET assemblies, Dotfucator from PreEmptive Solutions is one of the popular ones and their community edition is free and included with Visual Studio. If you are interested in buying other version, check out this comparison. The Dofuscator community edition has limited features and the professional edition is very expensive. So instead of gaining profits by protecting them from reverse engineering, we will end up spending a lot on Obfuscation.

One of the best alternate utility for obfuscating is ConfuserEx - it is a completely free and opensource. You can ConfuserEx download from here.

After downloading, extract the zip into a folder and then run ConfuserEx.exe.

image

Drag and drop the EXE you want to protect on the ConfuserEx or you can manually select Base Directory, Output Directory and add the DDL or EXE.

image

Once you have done setting up the directories and adding DLL or EXE, go to the Settings tab in ConfuserEx. You can either add rules to Gobal settings or set individually for each DLL or EXE.

image

Click on “+” button, you will see “true” under Rules. Now click on edit rule (button below “-”).

image

On clicking edit rule, a new window will appear as shown below. Click on “+” button.

image

You can select different ways of adding levels of protection. If you want to learn Obfuscation in depth, check out this article.

image

Select only with “Anti IL Dasm” and “Anti Tamper”, that is enough for making it hard enough to reverse engineer for the decompilers.

image

After you click on Done, go to Protect tab and click on Protect button.

image

image

You can find the protected DLL or EXE in the output directory selected.

image

Test the EXE or DLL generated by ConfusedEx and check if it is working as usual. Now try to decompile it with a decompiler.

image

As we can see, the confused DLL or EXE which gets generated by ConfuserEx cannot be decompiled any more.

License

This article, along with any associated source code and files, is licensed under The Microsoft Public License (Ms-PL)

Share

About the Author

Arun Endapally
Technical Lead Thomson Reuters
India India
No Biography provided

You may also be interested in...

Pro
Pro

Comments and Discussions

 
QuestionI don't understand ... Pin
RenniePet23-Jun-18 21:51
memberRenniePet23-Jun-18 21:51 
QuestionCommand line... Pin
Archimedes2424-May-18 22:01
memberArchimedes2424-May-18 22:01 
QuestionObvious answer Pin
Roland M Smith24-May-18 3:31
memberRoland M Smith24-May-18 3:31 
General[My vote of 1] Title should refer to .NET Pin
Peter Turtle23-May-18 7:48
professionalPeter Turtle23-May-18 7:48 
Question[My vote of 1] It's not an article! Pin
Thornik23-May-18 4:50
memberThornik23-May-18 4:50 
SuggestionA good start Pin
enhzflep23-May-18 0:52
memberenhzflep23-May-18 0:52 
QuestionObfuscators... Pin
dandy7222-May-18 12:20
memberdandy7222-May-18 12:20 
QuestionHow can I use that with an application that is deployed via ClickOnce ? Pin
Ahmad_kelany22-May-18 10:34
memberAhmad_kelany22-May-18 10:34 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Praise Praise    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

Permalink | Advertise | Privacy | Cookies | Terms of Use | Mobile
Web01-2016 | 2.8.180712.1 | Last Updated 22 May 2018
Article Copyright 2018 by Arun Endapally
Everything else Copyright © CodeProject, 1999-2018
Layout: fixed | fluid