Hey Michael, you can try ours, it's specifically designed to work along with certificate's instead of passwords: http://blog.authy.com/two-factor-ssh-in-thirty

Hey Michael, you can try ours, it's specifically designed to work along with certificate's instead of passwords: http://blog.authy.com/two-factor-ssh-in-thirty-seconds http://blog.authy.com/two-factor-ssh-in-thirty-seconds (disclaimer: I am a founder of the company).