1Duo provides simple two-factor authentication as a service via:
2
3    1.  Phone callback
4    2.  SMS-delivered one-time passcodes
5    3.  Duo mobile app to generate one-time passcodes
6    4.  Duo mobile app for smartphone push authentication
7    5.  Duo hardware token to generate one-time passcodes
8
9This package allows an admin (or ordinary user) to quickly add Duo
10authentication to any Unix login without setting up secondary user
11accounts, directory synchronization, servers, or hardware.
12