Password

A password is usually a short string of characters, which is supposed to be known only to the legitimate user of a system and is used to authenticate this user to the system, in order to grand him/her access. Different systems impose different constraints on how passwords can be constructed - i.e., minimum and maximum length, set of characters permitted for use and so on. More advanced systems allow the user of passphrases - very long strings characters, grouped into usually meaningful words or even sentences. High-security systems employ various additional means for authentication, such as biometrics, smart cards and so on.