Add a new encryption method

Hi, guys. How can I add a new encryption method in openwrt firmware? Or tell me which files are changing while compiling, when I switch AES/DES in Web interface

For which purpose would you like to change the encryption method, i.e. for the WiFi connection or the web interface or ...?

To encrypt data transmitted over wifi

So you're talking about the wireless encryption method you can set up in LuCI at "Wireless Security"?