Before explaining how to generate one-time passwords, we should go over an S/Key login prompt:
$ telnet himalia
Trying 18.26.0.186...
Connected to himalia.lcs.mit.edu.
Escape character is '^]'.
s/key 92 hi52030
Password:
Note that, before prompting for a password, the login program prints out the iteration number and seed which you will need in order to generate the appropriate key. You will also find a useful feature (not shown here): if you press return at the password prompt, the login program will turn echo on, so you can see what you are typing. This can be extremely useful if you are attempting to type in an S/Key by hand, such as from a printout.
If this machine were configured to disallow UNIX passwords over a
connection from my machine, the prompt would have also included the
annotation `(s/key required)', indicating that only S/Key one-time
passwords will be accepted.