AP File Protector is a program for protecting your private files and folders. It uses a well-known encryption algorithm, 256-bit Rindjael AES and lets you add a password protection. Very easy to use; you only have to click on the file to be protected via Windows Explorer and type a password in the dialog box. Once encrypted, the file is assigned a. Cyt extension. To unlock the file, click on it and then enter the appropriate password.