How to Prevent My .Net Dll to be decompiled

Dll is data link library that stores some of the important information within it. This shared library stores information about the data present in our application. Protecting this data from being decompiled from our application is very important when original coding of the application is on the client machine. In case of web-based applications, it is not mandatory to protect coding. If you want to prevent the dll from decompiling, you may be wondering, how to prevent my .net dll to be decompiled.

In case of applications developed using C# and VB.net or any applications developed using .net framework or visual Studio; the compilers convert the code into (Intermediate Language) IL. This IL code is very close to the original code and the rest of the compilation is to be done by Just In Time (JIT) compiler when the application is run. The IL code contains instances and static variables, methods and types in their original form even when the application is released. Therefore, it is essential that you prevent the code and the dll of the applications developed using these languages by some methods.

Here are some tips and suggestions that will help you in preventing decompilation of .net dll.

  • Decompilation is the process by which the machine level code is converted into human understandable form and this can be more easily done in case of .net applications.
  • Some of the tools that can easily decompile your .net dll’s are ILDASM and Reflector. These tools can convert your important code into readable form and your private property into an open source software product.
  • To prevent decompilation of the data link library or dll in .net or the application designed using any other language, the process of obfuscation is used.
  • We need to use  third party tools in preventing the decompilation of dll. These tools are called obfuscation tools.
  • The tools used in the process of obfuscation include Demeanor and Xenocode. Using these tools, you can easily obfuscate your code. Either you can use these third-party tools for obfuscating the code or there is a built in tool in Visual studio that will help you in obfuscating the code.
  • The obfuscation package provided with Visual Studio is Dotfuscator. This package will not function as all the other full-fledged tools do, but it will perform some primary tasks.
  • This process of obfuscation will not prevent the code entirely from being decompiled, but it will convert the code into a complicated format, which is hard to understand when the code is decompiled.
  • Process of linking can also be used in protecting the .net libraries from being decompiled. You will get a number of linkers to prevent the decompilation of the libraries in .net. These linkers are quiet expensive, but give a high level of protection to your system as compared to the obfuscators.
  • Obfuscating and linking tools should be used throughout the development life cycle to ensure proper security.
  • Securing your code is also an important step that should be carried out while you are developing the code. If you provide high-level security to the code, it will be difficult to identify what your code does. Secured code will make it difficult for people to understand how your product exactly works.
  • Implementing proper license checking method is also very important while you are developing the code to prevent the dll from decompiling.

Following the suggestions given above, you will be able to prevent your .net dll from being decompiled and provide protection to some vital information of your application.


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