A passphrase is similar to a password but is usually longer and something memorable to the user. There are three basic ways in which authentication can be performed: • Something the user knows: This is authentication by what a user has knowledge of such as ATM card PINs, usernames and passwords, etc. • Something the user has: This is authentication by something the user possesses such as smart cards, tokens, etc. • Something the user is: Authentication in this case is by a physical feature unique to the user such as fingerprints, retina, etc.