The library can be used to create software token (don’t forget to protect the key of the token…). Usually the token generator is executed on a different device (e.g. a phone with a browser with javascript enabled) than the one using the OTP authentication.

If you want to use the library, you’ll need to load the crypto-js (sha1 and hmac) and hotp.js.

Calling the library is easy, you just have to set the hex key of the token, the counter plus the output format.

 otp = hotp("3132333435363738393031323334353637383930","4","dec6");

Current output formats are : hex40 (format used by Open OTP, a free software library) and dec6 (the 6 decimal digit as described in the RFC 4226).

A sample page with the test vector : http://www.foo.be/hotp/example.html