It is possible to generate SSH key pair in Linux with ssh-keygen command.
A file will be requested wherein the key should be saved along with the passphrase (password) for the key.
whb@host: ssh-keygen -t dsa Generating public/private dsa key pair. Enter file in which to save the key (/home/jolt/.ssh/id_dsa): Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in id_dsa. Your public key has been saved in id_dsa.pub. The key fingerprint is: 11:9e:ef:f2:14:a9:b9:c8:32:9c:b1:c3:c1:f5:d5:61 jolt@host
This will create a private key saved in /home/jolt/.ssh/id_dsa and a public key saved in /home/jolt/.ssh/id_dsa.pub
The passphrase is used whenever you connect using SSH.