C# WinForms hide encryption key

Question

I have a WinForms application which reads data from a sensitive file and performs calculations using that data. In order to keep the sensitive information from people's PCs, we decided to move the calculations to a web service, where the file will hide in a protected folder and only is accessible by the web service program itself.

Due to some complications it looks like it may not be possible to secure the server space in the required timeframe, so what we are now looking to do is use encryption to protect the file so that it can be safely distributed to people's PCs.

My question is this. Is is possible to encrypt a file (once, so a pre-encrypted file will be attached to the project) and then decrypt the file for use by the application without revealing

• The sensitive information inside the file
• The Encryption key used to decrypt the file

I know it is possible to generate source code from a .exe file so I would be looking for a solution that bears this in mind. I am new to this kind of app development so please excuse me if this is a stupid question and that what I am trying to do is not actually possible.

Cheers

Answer 1

No, it is not possible, you can only make it hard to do those two things. You can not make it impossible. All you can do is just make it hard enough it is not worth the effort to try, and that takes money to do (via specialized obfuscation software and paying experts in the field to look at your code and make it more secure)