Out of curiosity and interest I was wondering if anyone had come across any web based services which offer users other forms of authentication, other than the standard password or PIN? Or if authentication on the web can even reach beyond these methods?
closed as too broad by user10211, TildalWave, Adi, Xander, NULLZ Oct 25 '13 at 14:11
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Some ways of authentication that you haven't mentioned: third party (login with Facebook, Google) authentication, 2 factor authentication (text message, call to your phone, challenge-response token)
My health insurance, bank, and customs websites allow me to login using the Chip and PIN implemented in my national ID card if I have a reader connected to my computer.
Some services in my school's website require a client certificate as a 2nd factor for authentication.
There's no shortage of web apps which use something like source IP addresses as "authentication" if you consider that authentication. Try doing a security audit on an internal network for some big companies.. Some of the apps wont work any other way though.
We use SSL Client Certs on some Services, but you dont want to do this on "public" sites.