Erlang adaptation of HMAC-Based One-Time Password Algorithm, as described in RFC 4226.
Simplest example:
1> Secret = hotp_secret:new().
<<104,212,164,165,146,193,202,163,7,141,26,71,82,17,133,
95,108,68,35,130>>
2>
2> hotp:cons(Secret, 0).
130575
3>
See tests for more.