algorithmic password on sshd

Question

ok, i got this in my mind and curious if its possible. On linux systems, is there any way to generate a valid algorithmic password combination to login SSH, that we can generate valid password with a little application or device (like o some banks' internet interface,say a key generator if you wish) ? if its possible on sshd, application is not problem.

example scenario:

key generator generates key with an algorithm -> 124a5s589s6fqwer SSHd checks if generated key is valid, and lets login.

Answer 1

Check one-time-passwords (OTP). Here's an example

Answer 2

Yes, this is possible. This is exactly the private key authentification over SSH works.

The usual scenario is that the person who wants to log-in receives some kind of "challenge" (this could be a random number, but the current time is also possible if there is some way to ensure synchronous clocks). This challenge is then combined with a secret and the resulting password is sent back. Only if it matches, the person is allowed to log in.

The key authentication just keeps all those things in the background, so you never notice them. If you set a password for a private ssh key, this password will be used for accessing the secret to be combined with the challenge. It will never be transmitted to the other machine, so this is the safest way to use SSH.

This is exactly how those tan generators work in the background. With tan lists it is a bit different.