[gnoway]

I have a few of their basic model keys. They have implemented OATH-HOTP as well as their own OTP scheme and HMAC-SHA1 challenge-response. You can also embed a static password. The keys have two slots and both of them can be used for any of the supported schemes.

They have some fancier keys that support a 'universal 2 factor' standard which I think they may have had a hand in creating.

I've used mine in OATH-HOTP and HMAC-SHA1 along with KeePass to do two-factor on my password db. You do need a server-side or peer component to initially sync with to do OTP or challenge-response.

[Yubi_David]

The new U2F protocol removes the need to have a central authentication server - the authentication process is just between the U2F device and the authenticating service. For more details, you can see: https://developers.yubico.com/U2F/