What is HOTP: HOTP is a class that simplifies One Time Password systems for PHP Authentication. The HOTP/TOTP Algorithms have been around for a bit, so this is a straightforward class to meet the test vector requirements.

What works with HOTP/TOTP: It's been tested to the test vectors, and I've verified the time-sync hashes against the following:

• Android: Mobile-OTP
• iPhone: OATH Token

Why would I use this: Who wouldn't love a simple drop-in class for HMAC Based One Time Passwords? It's a great extra layer of security (creating two-factor auth) and it's pretty darn zippy.

Okay you sold me. Give me some docs:

• $result = HOTP::generateByCounter($key, $counter); // event based
• $result = HOTP::generateByTime($key, $window); // time based within a "window" of time
• $result = HOTP::generateByTimeWindow($key, $window, $min, $max); // same as generateByTime, but for $min windows before and $max windows after

with $result, you can do all sorts of neat things...

• $result->toString();
• $result->toHex();
• $result->doDec();
• $result->toHotp($length); // how many digits in your OTP?