Authentication is the process of how one proves that they are who they claim that they are. When one claims to be “Ahmet San” by logging into a computer as “ahmetsan”, the computer system will most likely ask him for a password. He has claimed to be that person by entering the name into the username field. This part is the identification process. However, now he must prove that he is really that person. This is the authentication part. Almost all user access control systems require a password.