I'm very new to encryption and I wanted to know if it is secure or just possible to use encryption on single chars. I did some research, but nothing to clear and i'm a bit confused. The modes I think it is possible to do it with are one-time pad, RSA and AES in counter mode.
These are probably wrong ,but I have no idea why. So please explain me why these can't be used or maybe can be used.
EDIT: since I'm building a keylogger I could just buffer up and encrypt the whole buffer, encrypting a single char is not necessary.