libpam-ssh | Single sign-on via private SSH key | Mehr ...
This pluggable authentication module (PAM) provides single sign-on behavior for secure shell (SSH). During login, users type a SSH passphrase and is authenticated if the passphrase successfully decrypts the user's SSH private keys. In the PAM session phase, an ssh-agent process is started and keys are added, and thus users can SSH to other hosts that accept key authentication without typing any passwords for the entire session.
