r. 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 glasses. A half-year trial in the USA gave encouraging but not perfect results. Less reliable are voice recognition and (handwritten) signatures. Mobile phones could use biometry to support e-commerce, most likely using fingerprints. The fact that we cannot change our biometrical identity might be a drawback if the stored identity is stolen. 6.7.2 RADIUS RADIUS is a flexible system, which can be used for many types of authentication services. Its original use was for dial-up connections to companies or to the Internet. The main idea is to protect and/or charge dial-up connections. The building blocks of a RADIUS system can be seen in Figure 6.15. Radius consists basically of a client and a server. The client, who is situated between the modem pool and the server, asks the user for identity and a password. A typical client location is a NAS, which is the access point to the Internet/intranet. The RADIUS server is nothi