mod_authn_otp - Apache module for one-time password authentication

mod_authn_otp is an Apache web server module for two-factor authentication
using one-time passwords (OTP) generated via the HOTP/OATH algorithm
defined in RFC 4226. This creates a simple way to protect a web site with
one-time passwords, using any RFC 4226-compliant hardware or software
token device. mod_authn_otp also supports the Mobile-OTP algorithm.

mod_authn_otp supports both event and time based one-time passwords. It
also supports "lingering" which allows the repeated re-use of a previously
used one-time password up to a configurable maximum linger time. This
allows one-time passwords to be used directly in HTTP authentication
without forcing the user to enter a new one-time password for every
page load.

mod_authn_otp supports both basic and digest authentication, and will
auto-synchronize with the user's token within a configurable maximum
offset (auto-synchronization is not supported with digest authentication).

WWW: http://mod-authn-otp.googlecode.com/