I'm evaluating potential two factor authentication solutions for a client and we're looking at standards-based TOTP (time-based one time password, you know, you have an app on your phone, it shows a number that changes every sixty seconds, and you have to enter the current one to get authenticated).
What I'd really like is a radius server that authenticates TOTP that can be on the back side of a dial-up VPN solution. I can't find anything like that from some web searching. Is anyone familiar with drop-in solutions like that?