$ ssh-keygen -t dsa
Generating public/private dsa key pair.
Enter file in which to save the key (/home/pierrick/.ssh/id_dsa): /home/pierrick/.ssh/id_dsa2
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: /home/pierrick/.ssh/id_dsa2.pub.
Your identification has been saved in /home/pierrick/.ssh/id_dsa2.
Your public key has been saved in /home/pierrick/.ssh/id_dsa2.pub.

Add the content of /home/pierrick/.ssh/id_dsa2.pub into remote ~/.ssh/authorized_keys

$ export EDITOR=vi; crontab -e
* * * * * ssh -i /home/pierrick/.ssh/id_dsa2 remote_user@remote_server 'echo $(date) >> /tmp/pierrick.log'

And see that every second, the date is appended to the remote /tmp/pierrick.log