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- How does Google Authenticator work? 3 answers
I'm trying to understand How google authenticator - counter based work. I have tried googling around finding a demo or at least how this work. I understand its a one time password but not like TOTP. I am already working on TOTP but i'm terribly having issue with time sync, because i'm working on an offline PC. So the windows time - well every 2 days or so the time keep shifting two or three seconds ahead.
Anyways, I am looking for a PHP code for HOTP counter based . I have found one or two examples but they have so many missing files.
Please, I would like to find a tutorial about that in PHP language or at least a basic idea to start with. BTW i found this http://www.ietf.org/rfc/rfc4226.txt .