Passwords may be used in many situations where a user needs to be authenticated. Situations requiring authentication may include the ability to access or use a computer, mobile phone, PDA, or any other device. They may also enable access to a physical location, or allow use of a credit/debit card or similar instrument. Passwords are typically alpha-numeric strings or sequences entered on a keyboard. Graphical authentication systems, where passwords are comprised of graphical components, also exist.
Like reference numerals are used in the drawings to denote like elements and features.