This is a server implementation in PHP for utilising Yubikey timestamps for more secure logins. It supports multiple OTPs at once for more secure one-time logins and the handling of OTPs during session logins.

The implementation utilises the Yubikey API protocol for verification of OTPS as implemented in

http://code.google.com/p/yubikey-val-server-php/

For more information read the introduction at

http://code.google.com/p/yubikey-timedelta-server-php/wiki/Introduction