I have a maybe simple or maybe strange question.
I'm just looking for how is this normally dealt with, what is the practice?
For a Windows form application to access a SQL server, (or other things) it will need that login information available somewhere, somewhere also the user will have access to. At the same time you might not want everyone in your organization to have direct SQL access to your database. So you'll need to protect this type of information, even from the users.
At the same time I understand it's relatively easy to de-compile any .net program and get back to something very close to the source code. So even things written in your code is not really "safe".
Connection strings I assume you would often want to put into a separate file so it's easy to change, without having to re-compile and distribute your program. You can encrypt that in the file so it can't easily be read by anyone. But you need to keep the key to de-crypt it again somewhere. I'm guessing this would normally be kept in the code itself and not saved externally in plain text. (You can't encrypt the key used to de-crypt the same key.)
So if anyone can de-compile your .net code, read through the code and find the key (and salt value etc) they also know how to de-crypt the connection string.
Then how do you protect that "application secret"?
I can think of a few ways to try to deal with it.
-Tools to obscure your code (code obfuscation, I guess is the correct term) would make it more difficult to find the key, I guess?
-In terms of SQL login you move the security to the SQL server and limit the application user - can't login with Management Studio, can only run stored procedures etc.
-If other languages is harder to de-compile or disassemble, maybe create a .dll in for example C that handles the de-cryption?
So how do you normally protect information like encryption key etc?