Using scp without password login

$ ssh-keygen -t dsa
Generating public/private dsa key pair.
Enter file in which to save the key (/home/udanax/.ssh/id_dsa):
Created directory '/home/udanax/.ssh'.
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/udanax/.ssh/id_dsa.
Your public key has been saved in /home/udanax/.ssh/id_dsa.pub.
The key fingerprint is: blah~ blah~
$ _

and, then

$ cat ~/.ssh/id_dsa.pub | ssh id@host "cat >> .ssh/authorized_keys"
password: enter the password