#Creating and using keypairs http://sshkeychain.sourceforge.net/mirrors/SSH-with-Keys-HOWTO/SSH-with-Keys-HOWTO-4.html#ss4.1
ssh-keygen -t dsa
Passphrase: a1b2c3d4e5
Saved in ~/.ssh
Now we have two files the key (private) and key.pub (public)
The key.pub should be in the server
cat key.pub >> ~/.ssh/authorized_keys to copy the public key in the server
The first time for login should require the passphrase
We were using ssh protocl version2