Google is one of the major proponents of U2F, which is based on hardware tokens. Yubikeys support it, either the cheap U2F-only one or a Neo / 4. I use it and i

Google is one of the major proponents of U2F, which is based on hardware tokens. Yubikeys support it, either the cheap U2F-only one or a Neo / 4. I use it and it works flawlessly. At the moment, only Chrome implements the required APIs as far as I know, but Mozilla is working on adding it to Firefox.