- Important when you don't trust the computer you are using, such as a library computer or internet kiosk.
- Available by default in Free/Net/Open BSD.
- FreeBSD uses OPIE, Net/Open use S/Key.
- One time passwords are based on your pass phrase, a non-repeating sequence number, and a seed.
- Initial setup should be done directly on the server.
- "skeyinit" for Net/Open, "opiepasswd -c" for FreeBSD.
- Enter a pass phrase that is not your regular account password.
- Find your current sequence number and seed with "opieinfo" or "skeyinfo", for example: "497 pc5246".
- Generate a list of the next 10 passwords and write them down, using "opiekey -n 10 497 pc5246" or "skey -n 10 497 pc5246".
- When you log in from a remote machine that might have a keystroke logger, you can now use a one time password instead of your regular password.
- For OpenBSD, log in as account:skey, for example "bob:skey", which will cause the system to present the s/key challenge.
- For NetBSD, the system will always present you with the s/key challenge if it is configured for your account, although you can still use your regular password.
- FreeBSD by default will force you to use a one time password if it is configured for your account.
- If you want both OPIE and password authentication, FreeBSD allows you to list trusted networks or hosts in /etc/opieaccess.
- Instead of carrying a list of passwords around, you can use s/key generators on a portable device that you trust, such as a palm pilot.
- For more info, check the man pages.