title: Attach hidden information to txt file in c#
body: <p>I'm building a simple cryptography application which be able to encrypt and decrypt a text inside any given txt file. The decryption proccess should determine which encryption type was used on the text, and with that type decrypt the specified txt files text.
  My question is, is there any way to attach a hidden information to a txt file which I will be able to read in the decryption proccess.
  Edit:
  What I mean by hidden, is that the user will not be able to see it in any way. It also should not reflect on the encrypted text.</p>