The following page on LifeHacker explains it quite well: http://lifehacker.com/5932700/please-turn-on-two+factor-authentication http://lifehacker.com/5932700/pl

The following page on LifeHacker explains it quite well: http://lifehacker.com/5932700/please-turn-on-two+factor-authentication http://lifehacker.com/5932700/please-turn-on-two+factor-auth... The application I wrote works for all the mentioned websites, e.g. Drupal, Amazon, Dreamhost, Dropbox, etc since it implements the standard HOTP specification. It is merely named G since this is the most well-known implementation and was my first use-case.