libpam-ssh | Authenticate using SSH keys | Mehr ...
This pluggable authentication module (PAM) provides single sign-on using secure shell (SSH) keys. During authentication, the user types 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 decrypted keys are added, and thus the user can SSH to other hosts that accept key authentication without typing more passwords for the entire session.