===Key Preparation===To use U2F on the yubikey, one must first enable U2F mode (only supported on NEO and 4). The U2F-only yubikey and the yubikey edge already supports U2F out of the box, and Yubikeys purchased from the VT Bookstore also have U2F enabled.

===Install Packages===You may need to install an extra package if using Linux. It doesn't seem to be required on Ubuntu 16.04, but does on Fedora 24.For Fedora: sudo dnf install libu2f-host ===Using with Virginia Tech 2-Factor (Duo)===There are two ways to use two factor with CAS login. Both will require Chrome (Chromium may work, but is currently untested). Option 2 allows Firefox usage after the initial setup. 1. Open Chrome. When logging in using CAS, the Duo popup will open asking what source to use for two factor. On the sidebar, click add device. It will want to confirm using an existing method first. Then, select that you want to enroll a U2F devices token. Follow the instructions onscreen to enroll. Once completed, you can be self-registeredjust tap your Yubikey (or other U2F token) to authenticate. 2. This is only if you want to use Firefox and still want to use U2F. First, setup U2F using Chrome. Then, download the Firefox U2F extension and UAControl. Setup UAControl to send a Chrome User Agent to login.vt.edu instead of the normal Firefox one, however and it only can be used on Chromeshould then allow you to use 2FA under Firefox.  See the [https://wiki.archlinux.org/index.php/Yubikey#Enabling_U2F_in_the_browser Arch Wiki]for more information.