cd /etc/ssh
sudo ssh-keygen -t rsa -f ssh_host_rsa_key -C '' -N ''
sudo chmod 600 ssh_host_rsa_key
sudo chmod 644 ssh_host_rsa_key.pub
sudo ssh-keygen -t dsa -f ssh_host_dsa_key -C '' -N ''
sudo chmod 600 ssh_host_dsa_key
sudo chmod 644 ssh_host_dsa_key.pub
/etc/init.d/ssh restart