Authentication serves as proof that you are who you say you are or what you claim to be.
Authentication is critical if there is to be any trust between parties. Authentication is required
when communicating over a network or logging onto a network. When communicating over a
network you should ask yourself two questions: 1) With whom am I communicating? and 2)
Why do I believe this person or entity is who he, she, or it claims to be? If you don't have a
good answer for question 2, then chances are you are wrong on question 1.
When logging onto a network, three basic schemes are used for authentication. Very often
networks will use a combination of more than one of the schemes-something you know,
something you have, and something you are-which are described as follows.