CentOS and OTP

[lancherider]

I'm looking for a backup way to do software OTP on CentOS.

Let me give a little background. At work, we're already using Yubikeys for hardware tokens, but a recent failure of the backend authentication server left us with absolutely no way to log into our systems other than rebooting into single user mode, which got me thinking, how can we give ourselves a secure way of logging in even if our auth server goes down? I have used S/KEY on BSD systems in the past, and there's even smartphone apps that will generate S/KEY tokens. That's very convenient, but I am having trouble finding a recent port to linux.

I have looked into OPIE and OTPW, but it's been so long since they were under serious development and I'd really like something that has some recent traction. Is anyone else using something that works well, especially using S/KEY and/or PAM? If so, what? Thanks much for any feedback!

[KermitDaFragger]

As a fallback you could create a user with a strong password (ie. 20 random characters which you keep on a piece of paper in a safe) who can only log on to TTY1 (ie. the physical terminal with mouse, keyboard, etc ) ? Its low tech and easy to implement.

There is also OTPW (One time passwords): http://www.cl.cam.ac.uk/~mgk25/otpw.html