Authentication methods are used to assure that a user has a claimed identity. These methods can be based on knowledge (e.g. a password or a key), on a token (e.g. a smart card), or on biometrics (e.g. a human fingerprint). Different methods can be combined to strengthen the assurance. If two methods are combined, this is called two-factor authentication, e.g. smart cards typically need to be unlocked by a PIN.

Use this tag if your question is primarily concerned about authentication mechanisms. If you tag your question with , then avoid the tag unless your question is about the security of a particular mechanism.

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