Editing Authentication (section)

==== Multi-factor authentication ====
{{Main|Multi-factor authentication}}

Multi-factor authentication involves two or more authentication factors (something you know, something you have, or something you are). Two-factor authentication is a special case of multi-factor authentication involving exactly two factors.<ref name="Turner-DigitalAuthentication-Basics" />

For example, using a bank card (something the user has) along with a PIN (something the user knows) provides two-factor authentication. Business networks may require users to provide a password (knowledge factor) and a pseudorandom number from a security token (ownership factor). Access to a very-high-security system might require a [[mantrap (access control)|mantrap]] screening of height, weight, facial, and fingerprint checks (several inherence factor elements) plus a PIN and a day code (knowledge factor elements),<ref>{{Cite book |last1=Ali |first1=Saqib |title=Cyber Security for Cyber Physical Systems |last2=Al Balushi |first2=Taiseera |last3=Nadir |first3=Zia |last4=Khadeer Hussain |first4=Omar |publisher=[[Springer Nature]] |year=2018 |isbn=978-3-319-75879-4 |series=Studies in Computational Intelligence |language=en |chapter=ICS/SCADA System Security for CPS |doi=10.1007/978-3-319-75880-0 |eissn=1860-9503 |issn=1860-949X}}</ref> but this is still a two-factor authentication.