dentities by answering one or more short questions. However, some people consider the system inconvenient, which may lead to churn. Some common authentication methods use RADIUS (remote authentication dial-in user service) and LDAP (lightweight directory access protocol). See below. It is important to understand that the right response is not a guarantee that we are directly communicating with the right party. There is a very serious attack called 'man in the middle'. Let us take an example from the real world. Mallory claims that he is a master chess player although he is not. If some chess master challenges him to play, Mallory arranges the game to happen in the computer network. Then Mallory challenges still another chess master. When the first master makes a move, Mallory mediates it to another master. They both think that they are playing with Mallory - but actually they Security are playing against each other. The same can be easily done in the Internet where a challenged party can quickly challenge the right party and give the right answer. The solution to the man in the middle attack is to carefully combine authentication and key exchange. 6.7.1 BIOMETRICS Biometric recognition uses fingerprints, faces, the iris and other parts of the body for identification. If successful and affordable, such methods can fully replace identity cards, codes and passwords. This will no doubt make life easier, since we won't have to carry identification cards or keys or remember a lot of digits any more. Biometrics is nothing new. The old Egyptians used it to handle 'secure transactions' when the society became more organized and anonymous. The biggest advantage is that nobody can steal your biometric identity as opposed to keys and codes. Computer-supported biometry came into use in criminology for comparing a fingerprint with fingerprints in a catalogue. One of the safest methods is scanning of the iris. The technique was initially developed in Cambridge. Even twins have different iris. Scanning is possible also with glas