~/.ssh/authorized_keys
         Lists the public keys (RSA/DSA) that can be used for logging in
         as this user.  The format of this file is described above.  The
         content of the file is not highly sensitive, but the recommended
         permissions are read/write for the user, and not accessible by
         others.

         If this file, the ~/.ssh directory, or the user's home directory
         are writable by other users, then the file could be modified or
         replaced by unauthorized users.  In this case, sshd will not
         allow it to be used unless the StrictModes option has been set to
         “no”.

PasswordAuthentication no

sudo /etc/init.d/ssh restart

chmod 600 /data/dropbear/.ssh/authorized_keys

chmod 700 /data/dropbear/.ssh/authorized_keys # In case of MacOS X 10.6-10.8

chmod 755 /data/dropbear/ /data/dropbear/.ssh

$ ec2-authorize default -p 22

$ ec2-authorize default -p 22 --region us-west-1