'''Two-factor authentication''' is an [[authentication]] [[protocol]] that requires two forms of authentication to access a system.
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The first factor in the authentication may be something the user knows such as a password or [[Personal Identification Numer|PIN]]. The second factor may be something the user has or is such as a card, token, electronic badge, fingerprint or retinal pattern ([[biometrics]]).
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This contrasts with traditional password authentication which requires that a user
