!!! Overview[1]
[{$pagename}] is an ([HOTP]) is a cornerstone of Initiative For Open Authentication [Initiative for Open Authentication].

[{$pagename}] is a [One-Time Password System]

[{$pagename}] is an specific algorithm to create [One-Time password].

[{$pagename}] was published as an informational IETF [RFC 4226] in December 2005, documenting the algorithm along with a Java implementation. 

Since then, the [{$pagename}] algorithm has been adopted by many companies worldwide. The [{$pagename}] algorithm is a freely available open standard.

[{$pagename}] uses a secret key and a counter as input to the HMAC-SHA1 [Message Authentication Code] (MAC) algorithm, truncates the calculated MAC value and converts it to a to human readable code, usually a 6-digit number. 


!! More Information
There might be more information for this subject on one of the following:
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* [#1] - [HMAC-based One Time Password algorithm|https://en.wikipedia.org/wiki/HMAC-based_One-time_Password_Algorithm|target='_blank'] - based on 2015-02-12.