Create keys on local machine

 ssh-keygen

Copy Public Key (id_dsa.pub) to PC you want to log into

 scp ~/.ssh/id_rsa.pub username@host:

On the PC you want to log into go to the .ssh folder in the home dir and add the key in to the authorised keys file

 cat id_rsa.pub >> .ssh/authorized_key

Thats it. The pub key can be deleted off the server your logging into. Job Done.

Original = http://www.redbrick.dcu.ie/help/tutorials/ssh_keys/